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Find video protocols related to scientific articles indexed in Pubmed.
A polymorphism (-455G>A) in the ?-fibrinogen gene is associated with an increased risk of cerebral infarction in the Chinese population: A meta-analysis.
J Renin Angiotensin Aldosterone Syst
PUBLISHED: 11-16-2014
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Previous studies have investigated the association between a polymorphism (-455G>A) in the ?-fibrinogen gene and the risk of cerebral infarction. However, these results are controversial. To shed light on these inconclusive findings, we performed a meta-analysis of studies relating the ?-fibrinogen genetic polymorphism (-455G>A) to the risk of cerebral infarction.
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Using the ubiquitous pH meter combined with a loop mediated isothermal amplification method for facile and sensitive detection of Nosema bombycis genomic DNA PTP1.
Chem. Commun. (Camb.)
PUBLISHED: 11-10-2014
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Here we show an amplification-coupled detection method for directly measuring released hydrogen ions during the loop mediated isothermal amplification (LAMP) procedure by using a pH meter. The genomic DNA of Nosema bombycis (N. bombycis) was amplified and detected by employing this LAMP-pH meter platform for the first time.
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Multiplexed and Amplified Electronic Sensor for the Detection of MicroRNAs from Cancer Cells.
Anal. Chem.
PUBLISHED: 11-06-2014
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The detection of microRNA expression profiles plays an important role in early diagnosis of different cancers. On the basis of the employment of redox labels with distinct potential positions and duplex specific nuclease (DSN)-assisted target recycling signal amplifications, we have developed a multiplexed and convenient electronic sensor for highly sensitive detection of microRNA (miRNA)-141 and miRNA-21. The sensor is constructed by self-assembly of thiol-modified, redox species-labeled hairpin probes on the gold sensing electrode. The hybridizations between the target miRNAs and the surface-immobilized probes lead to the formation of RNA/DNA duplexes, and DSN subsequently cleaves the redox-labeled hairpin probes of the RNA/DNA duplexes to recycle the target miRNAs and to generate significantly amplified current suppression at different potentials for multiplexed detection of miRNA-141 and miRNA-21 down to 4.2 and 3.0 fM, respectively. The sensor is also highly selective toward the target miRNAs and can be employed to monitor miRNAs from human prostate carcinoma (22Rv1) and breast cancer (MCF-7) cell lysates simultaneously. The sensor reported here thus holds great potential for the development of multiplexed, sensitive, selective, and simple sensing platforms for simultaneous detection of a variety of miRNA biomarkers for clinic applications with careful selection of the labels.
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Enhanced electrochemiluminescence sensor for detecting dopamine based on gold nanoflower@graphitic carbon nitride polymer nanosheet-polyaniline hybrids.
Analyst
PUBLISHED: 10-31-2014
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In this work, an enhanced electrochemiluminescence (ECL) sensor based on gold nanoflower@graphitic carbon nitride polymer nanosheet-polyaniline hybrids (AuNF@g-C3N4-PANI) was prepared for the detection of dapamine (DA). First, the bulk g-C3N4 was prepared through polymerizing melamine under 600 °C. And then the g-C3N4 nanosheet was obtained by ultrasonication-assisted liquid exfoliation of bulk g-C3N4. Finally, polyaniline (PANI) and gold nanoflowers (AuNFs) were successively formed on the g-C3N4 nanosheet through an in situ synthesis method. The resulting AuNF@g-C3N4-PANI hybrids were modified onto the surface of glassy carbon electrode to achieve a sensor (AuNF@g-C3N4-PANI/GCE) for detecting dopamine. Under the optimal conditions, the ECL signal increased linearly with the concentration of dopamine. The linear range of 5.0 × 10(-9) to 1.6 × 10(-6) M was obtained, while the detection limit was 1.7 × 10(-9) M. The prepared sensor exhibited a low detection limit and high sensitivity for the determination of dopamine. The combination of g-C3N4 nanosheet, PANI and AuNF would provide a new opportunity for the ECL sensor.
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Ultrasensitive immunoassay based on a pseudobienzyme amplifying system of choline oxidase and luminol-reduced Pt@Au hybrid nanoflowers.
Chem. Commun. (Camb.)
PUBLISHED: 10-15-2014
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A multi-functional luminol-reduced Pt@Au hybrid flower-like nanocomposite (luminol-Pt@AuNF) which not only acts as an efficient signal probe but also constitutes a pseudobienzyme amplifying system with choline oxidase (ChOx) was firstly synthesized and applied to the construction of a solid-state luminol electrochemiluminescence (ECL) immunosensor for cardiac troponin I (cTnI) detection.
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Bivalent histone modifications during tooth development.
Int J Oral Sci
PUBLISHED: 10-10-2014
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Histone methylation is one of the most widely studied post-transcriptional modifications. It is thought to be an important epigenetic event that is closely associated with cell fate determination and differentiation. To explore the spatiotemporal expression of histone H3 lysine 4 trimethylation (H3K4me3) and histone H3 lysine 27 trimethylation (H3K27me3) epigenetic marks and methylation or demethylation transferases in tooth organ development, we measured the expression of SET7, EZH2, KDM5B and JMJD3 via immunohistochemistry and quantitative polymerase chain reaction (qPCR) analysis in the first molar of BALB/c mice embryos at E13.5, E15.5, E17.5, P0 and P3, respectively. We also measured the expression of H3K4me3 and H3K27me3 with immunofluorescence staining. During murine tooth germ development, methylation or demethylation transferases were expressed in a spatial-temporal manner. The bivalent modification characterized by H3K4me3 and H3K27me3 can be found during the tooth germ development, as shown by immunofluorescence. The expression of SET7, EZH2 as methylation transferases and KDM5B and JMJD3 as demethylation transferases indicated accordingly with the expression of H3K4me3 and H3K27me3 respectively to some extent. The bivalent histone may play a critical role in tooth organ development via the regulation of cell differentiation.International Journal of Oral Science advance online publication, 14 November 2014; doi:10.1038/ijos.2014.60.
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A supersandwich electrochemiluminescence immunosensor based on mimic-intramolecular interaction for sensitive detection of proteins.
Analyst
PUBLISHED: 08-15-2014
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An electrochemiluminescence (ECL) immunoassay protocol was developed based on mimic-intramolecular interaction for sensitive detection of prostate specific antigen (PSA). It was constructed by integrating the ECL luminophore (tris(4,4'-dicarboxylicacid-2,2'-bipyridyl)-ruthenium(ii)dichloride (Ru(dcbpy)3(2+))) and coreactant (histidine) into the supersandwich DNA structure. This strategy was more effective in amplifying the ECL signal by shortening the electronic transmission distance, improving the ECL luminous stability and enhancing the ECL luminous efficiency. The ECL matrices denoted as MWCNTs@PDA-AuNPs were fabricated through spontaneous oxidative polymerization of dopamine (DA) on multiwalled carbon nanotubes (MWCNTs) and reducing HAuCl4 to produce gold nanoparticles (AuNPs) by DA simultaneously. Then, the prepared matrices were applied to bind capture antibodies. Moreover, supersandwich Ab2 bioconjugate was designed using a PAMAM dendrimer to immobilize the detection antibody and supersandwich DNA structure. The PAMAM dendrimer, with a plurality of secondary and tertiary amine groups, not only facilitated high-density immobilization of the detection antibody and supersandwich DNA structure, but also greatly amplified the ECL signal of Ru(dcbpy)3(2+). The supersandwich DNA structure contained multiple Ru(dcbpy)3(2+) and histidine, further amplifying the ECL signal. The proposed supersandwich immunosensor showed high sensitivity with a detection limit of 4.2 fg mL(-1) and a wide linear range of 0.01 pg mL(-1)-40.00 ng mL(-1). With the excellent stability, satisfying precision and reproducibility, the proposed immunosensor indicates promising practicability for clinical diagnosis.
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Highly efficient electrogenerated chemiluminescence quenching of PEI enhanced Ru(bpy)?²? nanocomposite by hemin and Au@CeO? nanoparticles.
Biosens Bioelectron
PUBLISHED: 08-01-2014
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In this work, a new signal amplified strategy based on the quenching effect of hemin and Au nanoparticles decorated CeO2 nanoparticles (Au@CeO2 NPs) for ultrasensitive detection of thrombin (TB) is reported for the first time. Herein, the poly(ethylenimine) (PEI) enhanced Ru(bpy)3(2+) nanocomposite was implemented by direct chemical polymerization, which could provide the desirable enhanced initial ECL signal. Furthermore, the detection aptamer of thrombin (TBA 2) was immobilized on Au@CeO2 NPs to form TBA 2/Au@CeO2 conjugates. Then, the G-rich DNA of TBA 2 sequence could fold into a G-quadruplex structure to embed hemin to obtain the quenching probe of hemin/TBA 2/Au@CeO2 conjugates. In the presence of target TB, the sandwiched structure could be formed between capture aptamer (TBA 1), TB and hemin/TBA 2/Au@CeO2 conjugates, thereby resulting in a proportional quenching in ECL response with TB, due to the quenching of both hemin and Au@CeO2 NPs. As a result, the signal-off aptasensor showed a wider linear range response from 10(-13) to 10(-8) M with lower detection limit of 0.03 pM.
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A super intramolecular self-enhanced electrochemiluminescence immunosensor based on polymer chains grafted on palladium nanocages.
Nanoscale
PUBLISHED: 07-29-2014
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An intramolecular self-enhanced electrochemiluminescent derivative is prepared by grafting polystyrene (PS)-based polymer chains with pendant Ru(ii) luminophore from poly(ethylenimine) (PEI) on the surface of palladium nanocages (PdNCs). In this way, the Ru(ii) luminophore and its co-reactive group (amine groups in PEI) exist in the same polymer molecule, which shortens the electronic transmission distance between them and enhances the luminous stability. Meanwhile, through atom transfer radical polymerization (ATRP), the loading amount of Ru(ii) luminophore is greatly increased. Therefore, the obtained electrochemiluminescent derivative (PdNC-PEI-PSRu) has high luminous efficiency and stability. Furthermore, due to their special nanostructures of porous walls and hollow interiors, PdNCs have great advantages in high specific surface areas and good electrocatalytic ability, which make them act as an excellent immobilized platform for PEI and detection antibody. Based on the sandwiched immunoreactions, a sensitive "signal on" electrochemiluminescence immunosensor is constructed for the detection of carbohydrate antigen 15-3 (CA 15-3). As a result, a wide linear range from 0.01 U mL(-1) to 120 U mL(-1) is acquired with a relatively low detection limit of 0.003 U mL(-1).
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Treatment with CA-074Me, a Cathepsin B inhibitor, reduces lung interstitial inflammation and fibrosis in a rat model of polymyositis.
Lab. Invest.
PUBLISHED: 07-19-2014
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Cathepsin B (CB) is involved in the turnover of proteins and has various roles in maintaining the normal metabolism of cells. In our recent study, CB is increased in the muscles of polymyositis/dermatomyositis (PM/DM). However, the role of CB in interstitial lung disease (ILD) has not been reported. ILD is a frequent complication of PM/DM, which is the leading cause of death in PM/DM. It carries high morbidity and mortality in connective tissue diseases, characterized by an overproduction of inflammatory cytokines and induced fibrosis, resulting in respiratory failure. The etiology and pathogenesis of ILD remain incompletely understood. This study investigated whether treatment with CA-074Me, a specific inhibitor of CB, attenuates ILD in PM. CB expression, inflammation, and fibrosis were analyzed in the lung tissues from patients with PM/DM. The animal model of PM was induced in guinea pigs with Coxsackie virus B1 (CVB1). CA-074Me was given 24?h after CVB1 injection for 7 consecutive days. At the end of the experiment, the animals were killed and lung tissues were collected for the following analysis. Inflammation, fibrosis and apoptosis cells, and cytokines were assessed by histological examinations and immunohistochemical analyses, western blot analysis and transferase-mediated dUTP nick-end labeling assay. In patients with PM/DM, the protein levels of CB were significantly elevated in lung tissues compared with healthy controls, which correlated with increases in inflammation and fibrosis. Similarly, the expression of CB, inflammation and fibrosis, CD8(+) T cell, CD68(+) cell, tumor necrosis factor-alpha, transforming growth factor-beta1 infiltrations, and apoptotic cell death were significantly increased in lung tissues of the guinea-pig model of CVB1-induced PM. These changes were attenuated by the administration of CA-074Me. In conclusion, this study demonstrates that PM/DM increases CB expression in lung tissues and inhibition of CB reduces ILD in a guinea-pig model of CVB1-induced PM. This finding suggests that CB may be a potential therapeutic target for ILD.Laboratory Investigation advance online publication, 10 November 2014; doi:10.1038/labinvest.2014.135.
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Serum Brain-derived neurotrophic factor levels in post-stroke depression.
J Affect Disord
PUBLISHED: 07-18-2014
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Depression is a frequent mood disorder that affects around a third of stroke patients and has been associated with poorer outcome. Our aim was to determine whether there is a relationship between serum Brain-derived neurotrophic factor (BDNF) levels and post-stroke depression (PSD).
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Neuroprotective Effects of ?-Asarone Against 6-Hydroxy Dopamine-Induced Parkinsonism via JNK/Bcl-2/Beclin-1 Pathway.
Mol. Neurobiol.
PUBLISHED: 07-05-2014
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?-asarone, a major component of Acorus tatarinowii Schott, has positive effects in neurodegeneration disease, however, its effect on the Parkinson's disease (PD) remains unclear. In this study, the effects of ?-asarone on behavioral tests, neurotransmitters, tyrosine hydroxylase (TH), and ?-synuclein (?-syn) were investigated in 6-hydroxydopamine (6-OHDA) induced rats. Furthermore, the JNK/Bcl-2/Beclin-1 autophagy pathway was also studied. The results showed that ?-asarone improved the behavioral symptoms of rats in the open field, rotarod test, initiation time, and stepping time. And it increased the HVA, Dopacl, and 5-HIAA levels in striatum but not the DA and 5-HT levels. After administration of ?-asarone, the TH level was elevated but the ?-syn was declined in rats. It inhibited the expressions of LC3-II, but increased the p62 expression in SN4741 cells. Moreover, it affected the expressions of Beclin-1, Bcl-2, JNK, and p-JNK in vivo. We deduced that ?-asarone may firstly downregulate expressions of JNK and p-JNK, and then indirectly increase the expression of Bcl-2. And the function of Beclin-1 could be inhibited, which could inhibit autophagy activation. Collectively, all data indicated that ?-asarone may be explored as a potential therapeutic agent in PD therapy.
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Toehold strand displacement-driven assembly of G-quadruplex DNA for enzyme-free and non-label sensitive fluorescent detection of thrombin.
Biosens Bioelectron
PUBLISHED: 07-02-2014
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Based on a new signal amplification strategy by the toehold strand displacement-driven cyclic assembly of G-quadruplex DNA, the development of an enzyme-free and non-label aptamer sensing approach for sensitive fluorescent detection of thrombin is described. The target thrombin associates with the corresponding aptamer of the partial dsDNA probes and liberates single stranded initiation sequences, which trigger the toehold strand displacement assembly of two G-quadruplex containing hairpin DNAs. This toehold strand displacement reaction leads to the cyclic reuse of the initiation sequences and the production of DNA assemblies with numerous G-quadruplex structures. The fluorescent dye, N-Methyl mesoporphyrin IX, binds to these G-quadruplex structures and generates significantly amplified fluorescent signals to achieve highly sensitive detection of thrombin down to 5pM. Besides, this method shows high selectivity towards the target thrombin against other control proteins. The developed thrombin sensing method herein avoids the modification of the probes and the involvement of any enzyme or nanomaterial labels for signal amplification. With the successful demonstration for thrombin detection, our approach can be easily adopted to monitor other target molecules in a simple, low-cost, sensitive and selective way by choosing appropriate aptamer/ligand pairs.
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Cleavage-based hybridization chain reaction for electrochemical detection of thrombin.
Analyst
PUBLISHED: 06-28-2014
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In the present work, we constructed a new label-free "inter-sandwich" electrochemical aptasensor for thrombin (TB) detection by employing a cleavage-based hybridization chain reaction (HCR). The designed single-stranded DNA (defined as binding DNA), which contained the thrombin aptamer binding sequence, a DNAzyme cleavage site and a signal reporter sequence, was first immobilized on the electrode. In the absence of a target TB, the designed DNAzymes could combine with the thrombin aptamer binding sequence via complementary base pairing, and then Cu(2+) could cleave the binding DNA. In the presence of a target TB, TB could combine with the thrombin aptamer binding sequence to predominantly form an aptamer-protein complex, which blocked the DNAzyme cleavage site and prevented the binding DNA from being cleaved by Cu(2+)-dependent DNAzyme. As a result, the signal reporter sequence could leave the electrode surface to trigger HCR with the help of two auxiliary DNA single-strands, A1 and A2. Then, the electron mediator hexaammineruthenium (III) chloride ([Ru(NH3)6](3+)) was embedded into the double-stranded DNA (dsDNA) to produce a strong electrochemical signal for the quantitative measurement of TB. For further amplification of the electrochemical signal, graphene reduced by dopamine (PDA-rGO) was introduced as a platform in this work. With this strategy, the aptasensor displayed a wide linearity in the range of 0.0001 nM to 50 nM with a low detection limit of 0.05 pM. Moreover, the resulting aptasensor exhibited good specificity and acceptable reproducibility and stability. Because of these factors, the fabrication protocol proposed in this work may be extended to clinical application.
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An electrochemical aptasensor for thrombin using synergetic catalysis of enzyme and porous Au@Pd core-shell nanostructures for signal amplification.
Biosens Bioelectron
PUBLISHED: 06-27-2014
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In this work, a sensitive electrochemical aptasensor for thrombin (TB) based on synergetic catalysis of enzyme and porous Au@Pd core-shell nanostructure has been constructed. With the advantages of large surface area and outstanding catalytic performance, porous Au@Pd core-shell nanostructures were firstly employed as the nanocarrier for the immobilization of electroactive toluidine blue (Tb), hemin/G-quadruplex formed by intercalating hemin into the TB aptamer (TBA) and glucose oxidase (GOx). As a certain amount of glucose was added into the detection cell, GOx rapidly catalyzed the oxidation of glucose, coupling with the local generation of H2O2 in the presence of dissolved O2. Then, porous Au@Pd nanoparticles and hemin/G-quadruplex as the peroxidase mimics efficiently catalyzed the reduction of H2O2, amplifying the electrochemical signal and improving the sensitivity. Finally, a detection limit of 0.037pM for TB was achieved. The excellent performance of the aptasensor indicated its promising prospect as a valuable tool in simple and cost-effective TB detection in clinical application.
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Electrochemiluminescence immunosensor using poly(l-histidine)-protected glucose dehydrogenase on Pt/Au bimetallic nanoparticles to generate an in situ co-reactant.
Analyst
PUBLISHED: 06-19-2014
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In this work, Pt/Au bimetallic nanoparticles (Pt/Au NPs) were used as nanocarriers to develop an electrochemiluminescence (ECL) immunosensor for sensitive cardiac troponin I (cTnI) detection, coupling with enzyme-based signal amplification. First, gold nanoparticles modified Ru(phen)3(2+)-doped silica nanoparticles (Au@RuSiO2 NPs) with numerous luminophores were used as a platform, potentially increasing the signal intensity. Second, Pt/Au NPs with large surface area and rich surface atoms were a superior matrix for the immobilization of numerous antibodies (Ab2), poly(l-histidine) (PLH) and glucose dehydrogenase (GDH). More importantly, the PLH-protected GDH exhibited excellent enzymatic activity for the oxidation of glucose accompanied by the reduction of NAD(+) to NADH. The in situ generated NADH acted as a co-reactant of Ru(phen)3(2+), significantly enhancing the ECL signal. In this manner, the designed immunosensor displayed high sensitivity for the detection of cTnI in the range of 0.010 ng mL(-1) to 10 ng mL(-1) with a detection limit of 3.3 pg mL(-1) (S/N = 3). The proposed strategy holds a new promise for highly sensitive bioassays for application in clinical analyses.
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In situ generation of self-enhanced luminophore by ?-lactamase catalysis for highly sensitive electrochemiluminescent aptasensor.
Anal. Chem.
PUBLISHED: 06-04-2014
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This work described a new electrogenerated chemiluminescence (ECL) aptasensor for ultrasensitive detection of thrombin (TB) based on the in situ generating self-enhanced luminophore by ?-lactamase catalysis for signal amplification. Briefly, a ruthenium complex (Ru-Amp), including two regions of [Ru(phen)2(cpaphen)](2+) and ampicillin (Amp), was synthesized as a self-enhanced ECL luminophore, which can produce an ECL signal through intramolecular interactions. Then, carbon nanotubes (CNTs) were used for immobilization of Ru-Amp via ?-? stacking interactions to form the Ru-Amp@CNTs nanocomposite. Using poly(ethylenimine) (PEI) as a linkage reagent, Au nanocages (AuNCs), owing to their electronic property and large surface areas, were decorated to the CNTs to form the Ru-Amp@CNTs-PEI-AuNCs nanocomposites, which were further used to immobilize thrombin binding aptamer II (TBA II) to form a signal probe (Ru-Amp@CNTs-PEI-AuNCs-TBA II). Through "sandwich" tactics, TBA II bioconjugates, TB and TBA I were immobilized onto the gold nanoparticles modified electrode. Then, with the enzyme catalysis of ?-lactamase, a novel self-enhanced ECL luminophore (Ru-AmpA) was in situ produced, which could exhibit a significant enhancement of ECL signal, due to the structure transformation of an amide bond into a secondary amine. A sandwich ECL assay for TB detection was developed with excellent sensitivity of a concentration variation from 1.0 fM to 1.0 pM and a detection limit of 0.33 fM. Therefore, the self-enhanced ECL luminophore, combining the further enhancement by in situ enzymatic reaction, is expected to have potential applications in biotechnology and clinical diagnosis.
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Manganese porphyrin-double stranded DNA complex guided in situ deposition of polyaniline for electrochemical thrombin detection.
Chem. Commun. (Camb.)
PUBLISHED: 05-24-2014
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In this work, we proposed a novel electrochemical strategy for sensitive detection of thrombin (TB) based on in situ generation of polyaniline (PANI) as a redox mediator by using a manganese porphyrin-double stranded DNA (MnTMPyP-dsDNA) peroxidase-like artificial enzyme mimic as a powerful catalyst and template.
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Ultrasensitive electrochemiluminescent detection of cardiac troponin I based on a self-enhanced Ru(II) complex.
Talanta
PUBLISHED: 05-14-2014
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To promote the luminous efficiency of luminophore, traditional electrochemiluminescence (ECL) immunoassay usually adopts the adding of coreactant into testing solution. However, many adverse micro-environmental factors in the solution are a limiting factor in ECL analytical techniques and received extensive attention. In our work, a self-enhanced ECL luminophore was synthesized by combining the coreactant (l-cysteine) and the luminophor (tris (4,4'-dicarboxylicacid-2,2'-bipyridyl) ruthenium(II) dichloride (Ru(dcbpy)3(2+))) to form one Ru(II) complex and was applied to fabricate a reagentless immunosensor for the detection of cardiac troponin I (cTnI) for the first time. Herein gold nanorods (AuNRs), due to their high specific surface area and good electrocatalytic ability, were used as carriers for the immobilization of Ru(II) complex and cTnI antibody to obtain the Ab2 bioconjugates as signal labels. The application of the self-enhanced Ru(II) complex not only avoided the addition of any coreactant into testing solution for simplifying the operation, but also achieved the intramolecular reaction for improving the ECL signal due to shorter electron transfer path and less energy loss. In view of these advantages, the proposed immunosensor achieved a wide linear range from 0.25 pg/mL to 0.1 ng/mL with an impressive detection limit of 0.083 pg/mL for cTnI (S/N=3).
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A reagentless electrochemiluminescent immunosensor for apurinic/apyrimidinic endonuclease 1 detection based on the new Ru(bpy)3(2+)/bi-arginine system.
Anal. Chim. Acta
PUBLISHED: 05-06-2014
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Apurinic/apyrimidinic endonuclease 1 (APE-1), a kind of multifunctional protein widely-distributed in the body, plays an essential role in the DNA base excision repair and serves as multiple possible roles in the response of human cancer to radiotherapy and chemotherapy. In this work, an ultrasensitive solid-state electrochemiluminescence (ECL) immunosensor is designed to determine APE-1 based on the new Ru(bpy)3(2+)/bi-arginine system. The bi-arginine (bi-Arg) is decorated on the Au nanoparticles functionalized magnetic Fe3O4/reduced graphene oxide (bi-Arg/Au@Fe3O4-rGO) according to the self-assembling and covalent cross-linking interaction to obtain the functionalized nanocomposite of bi-Arg/Au@Fe3O4-rGO. Herein, the bi-Arg/Au@Fe3O4-rGO plays not only an amplification label to enhance the ECL signal of Ru(bpy)3(2+) due to the coreactant of bi-Arg but also an ideal nanocarrier to load numerous secondary antibody. Based on sandwich-type immunoassay format, this proposed method offers a linear range of 1.0fgmL(-1)-5.0pgmL(-1) and an estimated detection limit of 0.3fgmL(-1) for the APE-1. Moreover, the reagentless ECL immunosensor also exhibits high sensitivity, excellent selectivity and good stability, which has greatly potential development and application in clinical diagnostics, immunology and biomedical research.
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A novel solid-state Ru(bpy)3(2+) electrochemiluminescence immunosensor based on poly(ethylenimine) and polyamidoamine dendrimers as co-reactants.
Talanta
PUBLISHED: 05-04-2014
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In this study, a novel solid-state Ru(bpy)3(2+) electrochemiluminescence (ECL) sandwiched immunosensor for sensitive detection of ?-fetoprotein (AFP) was constructed based on poly(ethylenimine) (PEI) functionalized reduced graphene oxide (PEI-rGO) and Au nanoparticles (AuNPs) decorated polyamidoamine (PAMAM) dendrimers. Both PEI and PAMAM are polymers with a lot of amino groups, which are able to serve as good co-reactant to remarkably enhance the ECL signal of Ru(bpy)3(2+). For improving the poor conductivity of PAMAM, the AuNPs were decorated on the amino groups of PAMAM. Through Au-N bonds, the formed AuNPs-PAMAM was decorated on the PEI-rGO. The obtained AuNPs-PAMAM/PEI-rGO was introduced to immobilize the detection antibody (Ab2). Then, the Ab2 labeled AuNPs-PAMAM/PEI-rGO was modified onto the glass carbon electrode surface via sandwiched immunoreactions. The ECL substrate was prepared by mixing nafion and the complex (Ru-PtNPs) of Pt nanoparticles (PtNPs) and Ru(bpy)3(2+), which could reduce the consumption of Ru complex, simplify the operation and enhance the ECL efficiency. The experimental results demonstrated that the proposed immunosensor had good response to AFP. The linear range was from 0.01 pg mL(-1) to 10 ng mL(-1) with a low detection limit of 3.3 fg mL(-1). Meanwhile, with satisfying stability, selectivity and reproducibility, the proposed sandwiched immunosensor was presented to possess good potential in clinical detection.
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A novel electrochemical aptasensor for highly sensitive detection of thrombin based on the autonomous assembly of hemin/G-quadruplex horseradish peroxidase-mimicking DNAzyme nanowires.
Anal. Chim. Acta
PUBLISHED: 04-28-2014
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In this work, a new signal amplified strategy was constructed based on isothermal exponential amplification reaction (EXPAR) and hybridization chain reaction (HCR) generating the hemin/G-quadruplex horseradish peroxidase-mimicking DNAzyme (HRP-mimicking DNAzyme) nanowires as signal output component for the sensitive detection of thrombin (TB). We employed EXPAR's ultra-high amplification efficiency to produce a large amount of two hairpin helper DNAs within a minutes. And then the resultant two hairpin helper DNAs could autonomously assemble the hemin/G-quadruplex HRP-mimicking DNAzymes nanowires as the redox-active reporter units on the electrode surface via hybridization chain reaction (HCR). The hemin/G-quadruplex structures simultaneously served as electron transfer medium and electrocatalyst to amplify the signal in the presence of H2O2. Specifically, only when the EXPAR reaction process has occurred, the HCR could be achieved and the hemin/G-quadruplex complexes could be formed on the surface of an electrode to give a detectable signal. The proposed strategy combines the amplification power of the EXPAR, HCR, and the inherent high sensitivity of the electrochemical detection. With such design, the proposed assay showed a good linear relationship within the range of 0.1 pM-50 nM with a detection limit of 33 fM (defined as S/N=3) for TB.
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An electrochemiluminescent microRNA biosensor based on hybridization chain reaction coupled with hemin as the signal enhancer.
Analyst
PUBLISHED: 04-12-2014
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In this study, a new universal biosensor based on luminol anodic electrochemiluminescence (ECL) for the detection of microRNA-155 was constructed by using hydrogen peroxide (H2O2) as a co-reactant and hemin as a catalyzer for signal amplification. The bare glassy carbon electrode (GCE) was first electrodeposited with Au nanoparticles (AuNPs). Then, helper DNA, which was partly complementary with the hairpin DNA chains, was assembled on the prepared GCE. Target microRNA-155 and the hairpin hybridization chains could create a formation of extended double-stranded DNA (dsDNA) polymers through the displacement of hybridization chains and the hybridization chain reaction (HCR). The HCR-generated dsDNA polymers give rise to the intercalation of a lot of hemin which could catalyze the oxidation of H2O2, leading to a remarkably amplified ECL signal output. The proposed biosensor showed a wide linear range from 5 fM to 50 pM with a relatively low detection limit of 1.67 fM for microRNA-155 detection. With excellent selectivity, good stability and high sensitivity, the proposed biosensor is promising in the development of a high-throughput assay of microRNA-155.
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Direct growth of Pt@Ag nanochains on tailorable graphene oxide with a green, in situ, template-free method and its biosensing application.
Analyst
PUBLISHED: 04-05-2014
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In this work, we have investigated the in situ growth of Ag nanochains (AgNCs) on carboxyl-functionalized graphene oxide based on enzymatic metalization for the first time. The merit of this method is that the AgNCs could be generated directly on carboxyl-functionalized graphene oxide in a natural, environmentally friendly and sustainable way with high productivity. Furthermore, the Pt nanoparticles were wrapped around the AgNCs (Pt@AgNCs) which manifested some superior functions, such as excellent electrical conductivity and well-defined electrochemical redox activity. With Pt@AgNCs as the electrochemical redox probe, we developed a label-free electrochemical aptasensor for highly sensitive detection of platelet-derived growth factor. A linear response was obtained over a wide range from 6 pM to 40 nM with a detection limit of 1.97 pM.
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High throughput immunosenor based on multi-label strategy and a novel array electrode.
Sci Rep
PUBLISHED: 04-03-2014
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Accurate prediction of a particular cancer can be achieved by measuring multiplex biomarkers. Traditional methods for multi-biomarkers detection are either multi-spots assay with chip or multi-label assay with one detection spot. However, the detection throughput of these two approaches is limited by the substrate area and the numbers of available label respectively. To solve this problem, in the present study, an immunoassay was firstly prepared by combining multi-label strategy and multi-spot assay with a novel array electrode for simultaneous detection of six biomarkers for hepatocellular carcinoma (HCC). The detection throughput of the proposed method was doubled in comparison with traditional multi-spots assay (one target protein was detected on each analytic spot), which could greatly enhance the sensitivity and specificity of HCC diagnosis. This detection model may serve as the starting point for high throughput of multianalyte assay.
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A novel strategy for synthesis of hollow gold nanosphere and its application in electrogenerated chemiluminescence glucose biosensor.
Talanta
PUBLISHED: 03-21-2014
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Well-distributed hollow gold nanospheres (Aushell@GOD) (20 ± 5 nm) were synthesized using the glucose oxidase (GOD) cross-linked with glutaraldehyde as a template. A glucose biosensor was prepared based on Aushell@GOD nanospheres for catalyzing luminol electrogenerated chemiluminescence (ECL). Firstly, chitosan was modified in a glassy carbon electrode which offered an interface of abundant amino-groups to assemble Aushell@GOD nanospheres. Then, glucose oxidase was adsorbed on the surface of Aushell@GOD nanospheres via binding interactions between Aushell and amino groups of GOD to construct a glucose biosensor. The Aushell@GOD nanospheres were investigated with TEM and UV-vis. The ECL behaviors of the biosensor were also investigated. Results showed that, the obtained Aushell@GOD nanospheres exhibited excellent catalytic effect towards the ECL of luminol-H2O2 system. The response of the prepared biosensor to glucose was linear with the glucose concentration in the range of 1.0 ?M to 4.3mM (R=0.9923) with a detection limit of 0.3 ?M (signal to noise=3). This ECL biosensor exhibited short response time and excellent stability for glucose. At the same time the prepared ECL biosensor showed good reproducibility, sensitivity and selectivity.
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An electrogenerated chemiluminescence sensor based on gold nanoparticles@C60 hybrid for the determination of phenolic compounds.
Biosens Bioelectron
PUBLISHED: 03-18-2014
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This paper described a novel strategy for the construction of an electrogenerated chemiluminescence (ECL) sensor based on gold nanoparticles@C60 (AuNPs@C60) hybrid for detecting phenolic compounds. First, C60 was functionalized with l-cysteine. Subsequently, with C60 as the core, gold nanoparticles (AuNPs) are synthesized and grown through an in situ reduction method in the presence of ascorbic acid (AA). The resulted flowerlike AuNPs@C60 nanoparticles were modified onto the glassy carbon electrode to achieve the sensor (AuNPs@C60/GCE). Here, l-cysteine not only can improve the biocompatibility and hydrophilicity of C60 but also can enhance the electrogenerated chemiluminescence (ECL) of peroxydisulfate system. Furthermore, both AuNPs and C60 are also beneficial to the ECL of the peroxydisulfate system. Due to the combination of l-cysteine, AuNPs and C60, the proposed ECL sensor exhibited an excellent analytical performance. Under an optimum condition, the ECL intensity increased linearly with phenolic compounds. The linear ranges of 6.2 × 10(-8)-1.2 × 10(-4)M, 5.0 × 10(-8)-1.1 × 10(-4)M and 5.0 × 10(-8)-1.1 × 10(-4)M were obtained for catechol (CC), hydroquinone (HQ) and p-cresol (PC), respectively, and the detection limits were 2.1 × 10(-8)M, 1.5 × 10(-8)M and 1.7 × 10(-8)M, respectively. The AuNPs@C60 hybrid might hold a new opportunity to develop an ECL sensor.
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Sensitive electrochemiluminescence detection for CA15-3 based on immobilizing luminol on dendrimer functionalized ZnO nanorods.
Biosens Bioelectron
PUBLISHED: 03-07-2014
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In this study, we constructed a novel electrochemiluminescence (ECL) immunosensor for sensitive and selective detection of carbohydrate antigen 15-3 (CA15-3) by using polyamidoamine (PAMAM)-functionalized ZnO nanorods (ZNs-PAMAM) as carriers. PAMAM dendrimers with hyper-branched and three-dimensional structure were used as linked reagents for co-immobilization of luminol and CA15-3 detection antibody on the ZNs to prepare the signal probe. In addition, ZNs could hasten the decomposition of H2O2 to generate various reactive oxygen species (ROSs) which accelerated the ECL reaction of luminol with amplified ECL intensity. Compared with luminol in the detection solution, the ECL efficiencies of luminol could be improved by immobilizing luminol on the electrode due to the smaller distance between luminescence reagent and the electrode surface. Moreover, the electrodepositing gold nanoparticles (AuNPs) on the bare glass carbon electrode (GCE) with enhanced surface area could capture a large amount of primary anti-CA15-3 to improve the sensitivity of the immunosensor. Under the optimized experimental conditions, a wide linear range of 0.1-120?U?mL(-1) was acquired with a relatively low detection limit of 0.033?U?mL(-1) (S/N=3) for CA15-3.
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Electrochemiluminescence recovery-based aptasensor for sensitive Ochratoxin A detection via exonuclease-catalyzed target recycling amplification.
Talanta
PUBLISHED: 02-19-2014
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Based on the recovery of the quantum dot (QD) electrochemiluminescence (ECL) and exonuclease-catalyzed target recycling amplification, the development of a highly sensitive aptasensor for Ochratoxin A (OTA) detection is described. The duplex DNA probes containing the biotin-modified aptamer are immobilized on a CdTe QD composite film-coated electrode. The presence of the OTA target leads to effective removal of the biotin-aptamers from the electrode surface via exonuclease-catalyzed recycling and reuse of OTA, which prevents the attachment of streptavidin-alkaline phosphatase (STV-ALP) through biotin-STV interaction. The electron transfer (ET) from the excited state CdTe QD ([CdTe](?)) to the electro-oxidized species of the enzymatic product of ALP during the potential scan is thus inhibited and the QD ECL emission is restored for quantitative OTA detection. Due to the exonuclease-catalyzed target recycling amplification, the inhibition effect of ET is significantly enhanced to achieve sensitive detection of OTA down to 0.64 pg mL(-1). The proposed method is selective for OTA and can be used to monitor OTA in real red wine samples. Our developed ECL recovery-based aptasensor thus offers great potential for the development of new ECL sensing platforms for various target analytes.
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Synthesis of multi-fullerenes encapsulated palladium nanocage, and its application in electrochemiluminescence immunosensors for the detection of Streptococcus suis Serotype 2.
Small
PUBLISHED: 02-19-2014
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A novel functionalized material is synthesized using surface-decorated fullerene (C60) to encapsulate hollow and porous palladium nanocages (PdNCs), and is applied to fabricate an electrochemiluminescence (ECL) immunosensor for the detection of Streptococcus suis Serotype 2 (SS2). PdNCs with hollow interiors and porous walls are prepared using a galvanic replacement reaction between silver nanocubes and metal precursor salts. Then, C60 reacts with L-cysteine (L-Cys) to form L-Cys functionalized C60 (C60-L-Cys), which has a better biocompatibility, conductivity, and hydrophilicity compared to C60 and possesses abundant -SH groups on the surface. Because of the special interaction between -SH and PdNCs, the obtained C60-L-Cys is adsorbed around the PdNCs to form an interesting structure with multiple spheres encapsulating the cage. The resultant functionalized material (C60 -L-Cys-PdNCs) has a high specific surface area, good electrocatalytic ability, and efficient photocatalytic activity, and is used to construct an ECL immunosensor for the detection of SS2. The ECL signal amplified strategy is performed by using the novel coreactant (C60-L-Cys) and in situ generation of O2 thus creating the S2O8(2-)-O2 ECL system. As a result, a wide linear detection range of 0.1 pg mL(-1) to 100 ng mL(-1) is acquired with a relatively low detection limit of 33.3 fg mL(-1).
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Terminal protection of small molecule-linked ssDNA for label-free and sensitive fluorescent detection of folate receptor.
Talanta
PUBLISHED: 02-18-2014
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In this work, based on terminal protection of folate-linked ssDNA (FA-ssDNA) and the SYBR Gold fluorescent dye, we describe the development of a label-free fluorescent strategy for the detection of folate receptors (FRs). The binding between the target FR and the FA moiety of the FA-ssDNA protects the FR bound FA-ssDNA from digesting by Exo I. The binding of SYBR Gold to the terminal protected, un-digested FA-ssDNA leads to enhanced fluorescent emission for the monitoring of FR with a detection limit of 30 pM. Besides, the developed method also shows high selectivity toward FR against other control proteins. Moreover, our approach avoids the labeling of the probes with fluorescent tags and achieves label-free detection of FR. With these advantages, the proposed method thus holds promising potential for the development of simple and convenient strategies for the detection of other proteins by using different small molecule receptor/protein ligand pairs.
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Dual-responses for electrochemical and electrochemiluminescent detection based on a bifunctional probe.
Chem. Commun. (Camb.)
PUBLISHED: 02-18-2014
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A bifunctional probe (PTC-Tb) which acts as not only a well-defined and stable electrochemical redox molecule but also as a highly efficient co-reactant of an electrochemiluminescent oxygen-peroxydisulfate system was firstly synthesized and applied to the construction of dual-response aptasensors for thrombin detection.
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Target-induced structure switching of DNA for label-free and ultrasensitive electrochemiluminescent detection of proteins.
Chem. Commun. (Camb.)
PUBLISHED: 02-13-2014
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The association of the target thrombin with the corresponding aptamer leads to structure switching of the dsDNA probes and the formation of nicking sites for exonuclease III, which causes cyclic cleavage of the dsDNA probes and highly reduced intercalation of the electrochemiluminescent signal indicators for label-free and sensitive detection of thrombin at the femtomolar level.
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An amplified electrochemical aptasensor for thrombin detection based on pseudobienzymic Fe3O4-Au nanocomposites and electroactive hemin/G-quadruplex as signal enhancers.
Analyst
PUBLISHED: 02-13-2014
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A sensitive and selective electrochemical aptasensor for thrombin detection was constructed based on hemin/G-quadruplex as the signal label and Fe3O4-Au nanocomposites with glucose oxidase (GOx-) and peroxide-mimicking enzyme activity as the signal enhancers. Due to their large surface area and good biocompatibility, Fe3O4-Au nanocomposites were employed to immobilize electroactive hemin/G-quadruplex, which was formed by the conjugation between a single-stranded guanine-rich nucleic acid and hemin. Based on the GOx-mimicking enzyme activity, Au nanoparticles on the surface of the Fe3O4-Au nanocomposites effectively catalyzed the oxidization of glucose in the presence of dissolved O2, accompanied by the production of H2O2. Both the Fe3O4 cores of Fe3O4-Au nanocomposites and hemin/G-quadruplex with H2O2-mimicking enzyme activity could catalyze the reduction of the generated H2O2, which promoted the electron transfer of hemin and amplified the electrochemical signal. The proposed electrochemical aptasensor had a wide dynamic linear range of 0.1 pM to 20 nM with a lower detection limit of 0.013 pM, which provided a promising method for a sensitive assay for the detection of proteins in electrochemical aptasensors.
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Amplified amperometric aptasensor for selective detection of protein using catalase-functional DNA-PtNPs dendrimer as a synergetic signal amplification label.
Biosens Bioelectron
PUBLISHED: 02-06-2014
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In this work, we present a new strategy to construct an electrochemical aptasensor for sensitive detection of platelet-derived growth factor BB (PDGF-BB) based on the synergetic amplification of a three-dimensional (3D) nanoscale catalase (CAT) enzyme-functional DNA-platinum nanoparticles (PtNPs) dendrimer through autonomous layer-by-layer assembly. Firstly, polyamidoaminedendrimer (PAMAM) with a hyper-branched and three-dimensional structure was served as nanocarriers to coimmobilize a large number of PDGF-BB binding aptamer (PBA II) and ssDNA 1 (S1) to form PBA II-PAMAM-S1 bioconjugate. In the presence of PDGF-BB, the bioconjugate was self-assembled on the electrode by sandwich assay. Following that, the carried S1 propagated a chain reaction of hybridization events between CAT-PtNPs-S1 and CAT-PtNPs-ssDNA 2 (S2) to form a 3D nanoscale CAT-functional PtNPs-DNA dendrimer, which successfully immobilized substantial CAT enzyme and PtNPs with superior catalysis activity. In this process, the formed negatively charged double-helix DNA could cause the intercalation of hexaammineruthenium(III) chloride (RuHex) into the groove via electrostatic interactions. Thus, numerous RuHex redox probes and CAT were decorated inside/outside of the dendrimer. In the presence of H2O2 in electrolytic cell, the synergistic reaction of CAT and PtNPs towards electrocatalysis could further amplify electrochemical signal. Under optimal condition, the CAT-PtNPs-DNA dendrimer-based sensing system presented a linear dependence between the reduction peak currents and logarithm of PDGF-BB concentrations in the range of 0.00005-35 nM with a relatively low detection limit of 0.02 pM.
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Plasma levels of glutamate during stroke is associated with development of post-stroke depression.
Psychoneuroendocrinology
PUBLISHED: 02-05-2014
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Depression is a frequent mood disorder that affects around 33% of stroke patient. Our aim was to test the possible association between plasma glutamate and the development of post-stroke depression (PSD) in Chinese patients.
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A pseudo triple-enzyme electrochemical aptasensor based on the amplification of Pt-Pd nanowires and hemin/G-quadruplex.
Anal. Chim. Acta
PUBLISHED: 02-01-2014
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Our present work aimed at developing a pseudo triple-enzyme cascade electrocatalytic electrochemical aptasensor for determination of thrombin with the amplification of alcohol dehydrogenase (ADH)-Pt-Pd nanowires bionanocomposite and hemin/G-quadruplex structure that simultaneously acted as NADH oxidase and HRP-mimicking DNAzyme. With the addition of ethanol to the electrolyte, the ADH immobilized on the Pt-Pd nanowires catalyzed ethanol to acetaldehyde accompanied by NAD(+) being converted to NADH. Then the hemin/G-quadruplex firstly served as NADH oxidase, converting the produced NADH to NAD(+) with the concomitant local formation of high concentration of H2O2. Subsequently, the hemin/G-quadruplex acted as HRP-mimicking DNAzyme, bioelectrocatalyzing the produced H2O2. At the same time, the Pt-Pd nanowires employed in our strategy not only provided a large surface area for immobilizing thrombin binding aptamer (TBA) and ADH, but also served as HRP-mimicking DNAzyme which rapidly bioelectrocatalyzed the reduction of the produced H2O2. Thus, such a pseudo triple-enzyme cascade electrochemical aptasensor could greatly promote the electron transfer of hemin and resulted in the dramatic enhancement of electrochemical signal. As a result, a wide dynamic concentration linear range from 0.2 pM to 20 nM with a low detection limit of 0.067 pM for thrombin (TB) determination was obtained. The excellent performance indicated that our strategy was a promising way for ultrasensitive assays in electrochemical aptasensors.
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A signal-on electrochemical aptasensor for ultrasensitive detection of endotoxin using three-way DNA junction-aided enzymatic recycling and graphene nanohybrid for amplification.
Nanoscale
PUBLISHED: 01-29-2014
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Endotoxin, also known as lipopolysaccharide (LPS), is able to induce a strong immune response on its internalization into mammalian cells. To date, aptamer-based biosensors for LPS detection have been rarely reported. This work describes a new signal-on electrochemical aptasensor for the ultrasensitive detection of LPS by combining the three-way DNA hybridization process and nanotechnology-based amplification. With the help of DNA1 (associated with the concentration of target LPS), the capture probe hybridizes with DNA1 and the assistant probe to open its hairpin structure and form a ternary "Y" junction structure. The DNA1 can be released from the structure in the presence of nicking endonuclease to initiate the next hybridization process. Then a great deal of cleaved capture probe produced in the cyclic process can bind with DNA2-nanocomposite, which contains the electroactive toluidine blue (Tb) with the amplification materials graphene (Gra) and gold nanoparticles (AuNPs). Thus, an enhanced electrochemical signal can be easily read out. With the cascade signal amplification, this newly designed protocol provides an ultrasensitive electrochemical detection of LPS down to the femtogram level (8.7 fg mL(-1)) with a linear range of 6 orders of magnitude (from 10 fg mL(-1) to 50 ng mL(-1)). Moreover, the high sensitivity and specificity make this method versatile for the detection of other biomolecules by changing the corresponding sequences of the capture probe and the assistant probe.
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Ultrasensitive electrochemiluminescent aptasensor for ochratoxin A detection with the loop-mediated isothermal amplification.
Anal. Chim. Acta
PUBLISHED: 01-25-2014
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In this study, we for the first time presented an efficient, accurate, rapid, simple and ultrasensitive detection system for small molecule ochratoxin A (OTA) by using the integration of loop-mediated isothermal amplification (LAMP) technique and subsequently direct readout of LAMP amplicons with a signal-on electrochemiluminescent (ECL) system. Firstly, the dsDNA composed by OTA aptamer and its capture DNA were immobilized on the electrode. After the target recognition, the OTA aptamer bond with target OTA and subsequently left off the electrode, which effectively decreased the immobilization amount of OTA aptamer on electrode. Then, the remaining OTA aptamers on the electrode served as inner primer to initiate the LAMP reaction. Interestingly, the LAMP amplification was detected by monitoring the intercalation of DNA-binding Ru(phen)3(2+) ECL indictors into newly formed amplicons with a set of integrated electrodes. The ECL indictor Ru(phen)3(2+) binding to amplicons caused the reduction of the ECL intensity due to the slow diffusion of Ru(phen)3(2+)-amplicons complex to the electrode surface. Therefore, the presence of more OTA was expected to lead to the release of more OTA aptamer, which meant less OTA aptamer remained on electrode for producing LAMP amplicons, resulting in less Ru(phen)3(2+) interlaced into the formed amplicons within a fixed Ru(phen)3(2+) amount with an obviously increased ECL signal input. As a result, a detection limit as low as 10 fM for OTA was achieved. The aptasensor also has good reproducibility and stability.
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Sensitive pseudobienzyme electrocatalytic DNA biosensor for mercury(II) ion by using the autonomously assembled hemin/G-quadruplex DNAzyme nanowires for signal amplification.
Anal. Chim. Acta
PUBLISHED: 01-25-2014
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Herein, a novel sensitive pseudobienzyme electrocatalytic DNA biosensor was proposed for mercury ion (Hg(2+)) detection by using autonomously assembled hemin/G-quadruplex DNAzyme nanowires for signal amplification. Thiol functionalized capture DNA was firstly immobilized on a nano-Au modified glass carbon electrode (GCE). In presence of Hg(2+), the specific coordination between Hg(2+) and T could result in the assembly of primer DNA on the electrode, which successfully triggered the HCR to form the hemin/G-quadruplex DNAzyme nanowires with substantial redox probe thionine (Thi). In the electrolyte of PBS containing NADH, the hemin/G-quadruplex nanowires firstly acted as an NADH oxidase to assist the concomitant formation of H2O2 in the presence of dissolved O2. Then, with the redox probe Thi as electron mediator, the hemin/G-quadruplex nanowires acted as an HRP-mimicking DNAzyme that quickly bioelectrocatalyzed the reduction of produced H2O2, which finally led to a dramatically amplified electrochemical signal. This method has demonstrated a high sensitivity of Hg(2+) detection with the dynamic concentration range spanning from 1.0 ng L(-1) to 10 mg L(-1) Hg(2+) and a detection limit of 0.5 ng L(-1) (2.5 pM) at the 3Sblank level, and it also demonstrated excellent selectivity against other interferential metal ions.
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Dynamic of neurochemical alterations in striatum, hippocampus and cortex after the 6-OHDA mesostriatal lesion.
Int. J. Dev. Neurosci.
PUBLISHED: 01-20-2014
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Immediate neurochemical alterations produced by 6-OHDA could explain the general toxic pattern in the central nervous system. However, no evidences describe the effects of 6-OHDA on early changes of neurotransmitters in rats' striatum, cortex and hippocampus. In our study, unilateral 6-OHDA injection into medial forebrain bundle (MFB) was used in rats, then five neurotransmitters were analyzed at 3, 6, 12, 24, 48 and 72 h, respectively. Results showed that 6-OHDA injection caused a sharp decline of striatal dopamine (DA) levels in the first 12h followed by a further reduction between 12 and 48 h. However, striatal levels of homovanillic acid (HVA) were stable in the first 12h and showed a marked reduction between 12 and 24h. Striatal levels of 5-hydroxytryptamine (5-HT) and 5-hydroxyindoleacetic acid (5-HIAA) decreased linearly for 72 h, whereas levels of norepinephrine (NE) showed a slight reduction in the first 48 h, and returned back to normal afterwards. Striatal HVA/DA ratio increased significantly in the first 12h, but 5-HIAA/5-HT ratio showed a sharp increase between 12 and 72 h. Besides, neurochemical alterations were also found in hippocampus and cortex, and the correlations of neurotransmitters were analyzed. Our study indicated that NE system had little influence in the early phase of 6-OHDA injection, moreover, early neurochemical alterations were involved with striatum, hippocampus and cortex.
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Electrochemical immunosensor for detecting the spore wall protein of Nosema bombycis based on the amplification of hemin/G-quadruplex DNAzyme concatamers functionalized Pt@Pd nanowires.
Biosens Bioelectron
PUBLISHED: 01-20-2014
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In this work, an ultrasensitive electrochemical immunosensor for detecting the Pebrine disease related spore wall protein of Nosema bombycis (SWP N.b) was fabricated based on the amplification of hemin/G-quadruplex functionalized Pt@Pd nanowires (Pt@PdNWs). The synthesized Pt@PdNWs possessed large surface area, which could effectively improve the immobilization amount of hemin/G-quadruplex DNAzyme concatamers produced via hybridization chain reaction (HCR). In the presence of SWP N.b, the hemin/G-quadruplex labeled Pt@PdNWs bioconjugations was captured on electrode surface and thus obtained electrochemical signal. After the addition of NADH into the electrolytic cell, hemin/G-quadruplex firstly acted as an NADH oxidase to locally produce H2O2 in the presence of dissolved O2. Then, the generated H2O2 would be quickly reduced via hemin/G-quadruplex as a horseradish peroxidase mimicking (HRP-mimicking) DNAzyme, which finally promoted the self-redox reaction of hemin/G-quadruplex and a greatly enhanced electrochemical signal was obtained. Furthermore, Pt@PdNWs with excellent electrocatalytic performance could also amplify electrochemical signal. With these amplification factors, the electrochemical immunosensor exhibited a wide linear range from 0.001 ng mL(-1) to 100 ng mL(-1) with a detection limit (LOD) of 0.24 pg mL(-1), providing a new promise for the diagnosis of Pebrine disease.
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Target recycling amplification for label-free and sensitive colorimetric detection of adenosine triphosphate based on un-modified aptamers and DNAzymes.
Anal. Chim. Acta
PUBLISHED: 01-19-2014
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Based on target recycling amplification, the development of a new label-free, simple and sensitive colorimetric detection method for ATP by using un-modified aptamers and DNAzymes is described. The association of the model target molecules (ATP) with the corresponding aptamers of the dsDNA probes leads to the release of the G-quadruplex sequences. The ATP-bound aptamers can be further degraded by Exonuclease III to release ATP, which can again bind the aptamers of the dsDNA probes to initiate the target recycling amplification process. Due to this target recycling amplification, the amount of the released G-quadruplex sequences is significantly enhanced. Subsequently, these G-quadruplex sequences bind hemin to form numerous peroxidase mimicking DNAzymes, which cause substantially intensified color change of the probe solution for highly sensitive colorimetric detection of ATP down to the sub-nanomolar (0.33nM) level. Our method is highly selective toward ATP against other control molecules and can be performed in one single homogeneous solution, which makes our sensing approach hold great potential for sensitive colorimetric detection of other small molecules and proteins.
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Highly enhanced electrochemiluminescence based on pseudo triple-enzyme cascade catalysis and in situ generation of co-reactant for thrombin detection.
Analyst
PUBLISHED: 01-17-2014
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In this work, a novel pseudo triple-enzyme cascade catalysis amplification strategy was employed to fabricate a highly sensitive electrochemiluminescence (ECL) aptasensor for thrombin (TB) detection. The signal amplification of the proposed aptasensor was based on the synergistic catalysis of glucose dehydrogenase (GDH) and hemin/G-quadruplex to generate a co-reactant in situ for the ECL of peroxydisulfate. Gold nanorods (AuNRs) conjugated with GDH and hemin/G-quadruplex were used as the secondary aptamer bioconjugate (TBA II) in this aptasensor. TB was sandwiched between TBA II and a thiol-terminated TB aptamer which self-assembled on the AuNRs-modified electrode. The pseudo triple-enzyme cascade catalysis was completed as follows: firstly, GDH could effectively catalyze the oxidation of glucose to gluconolactone, coupling with the reduction of ?-nicotinamide adenine dinucleotide hydrate (NAD(+)) into ?-nicotinamide adenine dinucleotide hydrogen (NADH). Then, the hemin/G-quadruplex acted as NADH oxidase, could rapidly oxidize NADH into NAD(+) accompanied with the generation of H2O2. Simultaneously, the hemin/G-quadruplex served as the horseradish peroxidase (HRP)-mimicking DNAzyme that further catalyzed the reduction of H2O2 to generate O2in situ. Then the O2 produced acted as the co-reactant of peroxydisulfate, resulting in significant ECL signal amplification and highly sensitive ECL detection. The proposed aptasensor showed a wide linear range of 0.0001-50 nM with a low detection limit of 33 fM (S/N = 3) for TB determination. The present work demonstrated that the novel strategy has great advantages of sensitivity, selectivity and reproducibility, which hold new promise for highly sensitive bioassays applied in clinical detection.
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Mediator-free triple-enzyme cascade electrocatalytic aptasensor with exonuclease-assisted target recycling and hybridization chain reaction amplification.
Biosens Bioelectron
PUBLISHED: 01-15-2014
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The amplified sensitive detection of protein is essential to biomedical research as well as clinical diagnosis. Here, we developed an ultrasensitive mediator-free triple-enzyme cascade electrocatalytic aptasensor for thrombin detection on the basis of exonuclease-assisted target recycling and hybridization chain reaction (HCR) amplification strategy. The double strands constructed by the hybridization of thrombin binding aptamer (S1) with its complementary strand (S2) were firstly assembled on the electrode. Upon addition of target to the system, the S1 recognized thrombin and left off electrode to make space for assembly of hybrid-primer probe (H0). Then, the H0 triggered the HCR to form the multi-functional hemin/G-quadruplex DNAzyme nanowires. In the mediator-free triple-enzyme cascade electrocatalytic amplification system, the hemin/G-quadruplex DNAzyme nanowires here simultaneously played three roles: the redox probe, NADH oxidase and HRP-mimicking DNAzyme, respectively, which effectively avoided the fussy redox probe and enzyme labeling process, serving a useful alternative or supplement to conventional assays that typically suffer from complexity and poor sensitivity. Additionally, in order to improve the assembly amount of hemin/G-quadruplex DNAzyme nanowire, the exonuclease-assisted target recycling amplification was used for the continuous removal of S1. As a result, the proposed method can detect thrombin specifically with a detection limit as low as 20 fM.
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Highly sensitive impedimetric immunosensor based on single-walled carbon nanohorns as labels and bienzyme biocatalyzed precipitation as enhancer for cancer biomarker detection.
Biosens Bioelectron
PUBLISHED: 01-15-2014
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A novel sandwich-type electrochemical immunosensor based on functionalized nanomaterial labels and bienzyme (horseradish peroxidase and glucose oxidase) biocatalyzed precipitation was developed for the detection of ?-fetoprotein (AFP). The enzymes linked to functionalized nanomaterials as biocatalysts could accelerate the oxidation of 4-chloro-1-naphthol (4-CN) by H2O2 to yield the insoluble product on the electrode surface; the mass loading of the precipitates on the device led to a significant enhanced signal. Cyclic voltammetry and electrochemical impedance spectroscopy techniques were used to monitor the enhanced precipitation of 4-CN that accumulated on the electrode surface and subsequent decrement in the electrode surface area by monitoring the reduction process of the Fe(CN)6(4-/3-) redox couple. Under optimal conditions, the proposed immunosensor showed a high sensitivity and a wide linear range from 0.001 to 60 ng mL(-1) with a low detection limit of 0.33 pg mL(-1). Moreover, the immunosensor exhibited good selectivity, acceptable stability and reproducibility. The amplification strategy showed good promise for clinical screening of tumor biomarkers.
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Amplified electrochemiluminescent aptasensor using mimicking bi-enzyme nanocomplexes as signal enhancement.
Anal. Chim. Acta
PUBLISHED: 01-15-2014
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In this work, a sandwich-type electrochemiluminescence (ECL) aptasensor for ultrasensitive detection of thrombin (TB) was designed based on mimicking bi-enzyme cascade catalysis to in situ generate coreactant of dissolved oxygen (O2) for signal amplification. We utilized hollow Au nanoparticles (HAuNPs) as carriers to immobilize glucose oxidase nanoparticles (GOxNPs) and Pt nanoparticles (PtNPs) by electrostatic adsorption. Then, the detection aptamer of thrombin (TBA 2) was immobilized on the PtNPs/GOxNPs/HAuNPs nanocomplexes. Finally, hemin was intercalated into the TBA 2 to obtain the hemin/G-quadruplex structure. The hemin/G-quadruplex was an interesting DNAzyme that commonly mimiced horseradish peroxidase (HRP). Herein, GOxNPs, hemin/G-quadruplex and PtNPs could form mimicking bi-enzyme cascade catalysis system to in situ generate dissolved O2 as coreactant in peroxydisulfate solution when the testing buffer contained proper amounts of glucose. This method had successfully overcome the disadvantage of difficulty to label the dissolved O2 and realized the ECL signal amplification. The experiment proved that the aptasensor had good linear relationship on low concentration of TB. The linear range was 1×10(-6)-10 nM, with a detection limit of 0.3 fM.
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Development of an electrochemical method for Ochratoxin A detection based on aptamer and loop-mediated isothermal amplification.
Biosens Bioelectron
PUBLISHED: 01-14-2014
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Loop-mediated isothermal amplification (LAMP) is an outstanding DNA amplification procedure, in which the reaction can accumulate 10(9) copies from less than 10 copies of input template within an hour. While the amplification reaction is extremely powerful, the quantitative detection of LAMP products is still analytically difficult. Besides, the type of targets that LAMP can detect is also less, which to some extent limited the application of LAMP. In this study, we are reporting for the first time an efficient and accurate detection system which employs the integration of LAMP, aptamer and the electrochemical method for the sensitive detection of Ochratoxin A (OTA). Aptamers were designed as the forward outer primer to trigger the LAMP reaction, and then the LAMP amplification products were combined with a redox active molecule methylene blue (MB) and analyzed by an electrode using differential pulse voltammograms (DPV). As the reaction progresses, the MB intercalated into double-stranded regions of LAMP amplicons reduces the free MB concentration. Hence, the peak current of reaction mixture decreased with the amplification because of the slow diffusion of MB-amplified DNA complex to the electrode surface. The peak height of the current was related to the input amount of the aptamers, providing a ready means to detection the concentration of OTA. With such design, the proposed assay showed a good linear relationship within the range of 0.001-50 nM with a detection limit of 0.3 pM (defined as S/N = 3) for OTA.
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A novel electrochemiluminescence aptasensor based on in situ generated proline and matrix polyamidoamine dendrimers as coreactants for signal amplication.
Biosens Bioelectron
PUBLISHED: 01-14-2014
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Here, an ultrasensitive electrochemiluminescence (ECL) aptasensor using in situ generated proline and polyamidoamine (PAMAM) dendrimers as coreactant for bis(2,2'-bipyridyl)(5-amino-1,10-phenanthroline) ruthenium(II) (Ru) was successfully constructed for detection of thrombin (TB). Firstly, PAMAM combined with PtNPs was used as platform to assemble substantial Ru, prolidase (GPDA) and avidin labeled thrombin aptamer (avidin-TBA) to form PAMAM-PtNPs-Ru-GDPA-TBA bioconjugate. With the double aptamer-based sandwich assay, the bioconjugate was successfully modified on the electrode surface. The proposed aptasensor possessed three attractive advantages: PAMAM, as a tertiary amine substance, not only served as a platform to immobilize the PtNPs for further assembling prolidase (GPDA) and avidin-TBA, but also used as a coreactant of Ru to amplify the ECL signal. Furthermore, putting the coreactant and luminescence reagent together onto the electrode surface could effectively shorten the reaction time, improve the efficiency of electron transfer, and enhance the ECL signal. Lastly, the in situ generated coreactant proline for Ru catalyzed by GPDA could rapidly increase the concentration of proline around the electrode surface, which could also greatly amplify the ECL signal. With the several amplification factors mentioned above, the proposed ECL aptasensor showed a wide linear range from 0.01 pmol L(-1) to 10 nmol L(-1) with the detection limit of 5.0 fmol L(-1). The experimental results also indicated that the aptasensor exhibited excellent selectivity, stability and reproducibility.
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Dual amplified and ultrasensitive electrochemical detection of mutant DNA Biomarkers based on nuclease-assisted target recycling and rolling circle amplifications.
Biosens Bioelectron
PUBLISHED: 01-08-2014
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Based on nicking endonuclease (NEase)-assisted target recycling and rolling circle amplification (RCA) for in situ generation of numerous G-quadruplex/hemin complexes, we developed a new, dual amplified and ultrasensitive electrochemical biosensor for mutant human p53 gene. The target mutant DNA hybridizes with the loop portion of a dithiol-modified hairpin probe (HP) self-assembled on a gold sensing electrode and forms nicking site for the NEase, which cleaves the HP and releases the target DNA. The released target DNA again hybridizes with the intact HP and initiates the DNA recycling process with the assistance of the NEase, leading to the cleavage of a large number of the HPs and the generation of numerous primers for RCA. With rationally designed, G-quadruplex complementary sequence-encoded RCA circular template, subsequent RCA results in the formation of long DNA sequences with massive tandem-repeat G-quadruplex sequences, which further associate with hemin and generate significantly amplified current response for highly sensitive DNA detection down to 0.25 fM. The developed method also exhibits high specificity for the target DNA against single-base mismatched sequence. With the ultrahigh sensitivity feature induced by the dual signal amplification, the proposed method can thus offer new opportunities for the detection of trace amounts of DNA.
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Procalcitonin sensitive detection based on graphene-gold nanocomposite film sensor platform and single-walled carbon nanohorns/hollow Pt chains complex as signal tags.
Biosens Bioelectron
PUBLISHED: 01-03-2014
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Septicemia is a serious disease that requires early diagnosis, and procalcitonin (PCT) serves as a diagnostic biomarker for this disease. Traditional clinical detection (via immune-gold chips) remains difficult and expensive. An electrochemical immunosensor based on new nanomaterials may provide a solving approach. Herein, an ultrasensitive sandwich electrochemical strategy for PCT detection was developed. Firstly, reduced graphene oxide (rGO)-gold (Au) nano-composite film was used as the immunosensor platform to increase the amount of PCT antibody 1(Ab1) immobilized. Next, single-walled carbon nanohorns (SWCNHs)/hollow Pt chains (HPtCs) complex was firstly utilized to label PCT Ab2 as signal tags. For SWCNHs with few side effects, high surface area and HPtCs with higher specific surface, better catalytic activity, complex synthesized from both may provide more advantages. Moreover, to amplify signal, HPtC catalytic activity with H2O2 was enhanced by horseradish peroxidase (HRP) for dual synergy amplification. The whole results demonstrated that the proposed immunosensor exhibited fast operation, high sensitivity, good reproducibility, acceptable stability and ideal selectivity compared with traditional method. The linear calibration of the immunosensor ranged from 1.00 pg/mL to 2.00 × 10(1)ng/mL with a detection limit of 0.43 pg/mL. Analytical application results revealed that the immunosensor matched with the real concentrations of serum samples. Overall this immunosensor may provide a new alternative strategy for PCT detection.
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Highly enhanced electrochemiluminescent strategy for tumor biomarkers detection with in situ generation of L-homocysteine for signal amplification.
Anal. Chim. Acta
PUBLISHED: 01-03-2014
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In this work, an ultrasensitive peroxydisulfate electrochemiluminescence (ECL) immunosensor using in situ generation of L-homocysteine (L-Hcys) for signal amplification was successfully constructed for detection of carcinoembryonic antigen (CEA). In the reaction of biological methylation, S-adenosyl-L-homocysteine hydrolase (SAHH) catalyzed the reversible hydrolysis of S-adenosyl-L-homocysteine (SAH) to produce L-Hcys, which was inducted into ECL system to construct the immunosensor for signal amplification in this work. Simultaneously, Gold and palladium nanoparticles functionalized multi-walled carbon nanotubes (Au-PdNPs@MWCNTs) were prepared, which were introduced to immobilize the secondary antibody (Ab2) and SAHH with high loading amount and good biological activity due to their improved surface area and excellent biocompatibility. Then the proposed ECL immunosensor was developed by a sandwich-type format using Au-PdNPs@MWCNTs-SAHH-Ab2 as tracer and graphene together with AuNPs as substrate. Besides the enhancement of Au-PdNPs, the enzymatic catalysis reaction also amplified the ECL signal dramatically, which was achieved by efficient catalysis of the SAHH towards the hydrolysis of SAH to generate improved amount of L-Hcys in situ. Furthermore, due to the special interaction between Au-PdNPs and -SH or -NH2 in L-Hcys, L-Hcys would gradually accumulate on the surface of the immunosensor, which greatly enhanced the concentration of L-Hcys on the immunosensor surface and further improved the ECL intensity. With the amplification factors above, a wide linear ranged from 0.1 pg mL(-1) to 80 ng mL(-1) was acquired with a relatively low detection limit of 33 fg mL(-1) for CEA.
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Ultrasensitive Apurinic/Apyrimidinic Endonuclease 1 Immunosensing Based on Self-Enhanced Electrochemiluminescence of a Ru(II) Complex.
Anal. Chem.
PUBLISHED: 12-30-2013
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An alternative "signal on" immunosensor for ultrasensitive detection of apurinic/apyrimidinic endonuclease 1 (APE-1) was designed utilizing the self-enhanced electrochemiluminescence (ECL) of a novel Ru(II) complex functionalized coil-like nanocomposite as signal labels. The desirable self-enhanced ECL luminophore was achieved by combining the coreactant of poly(ethylenimine) (PEI) and the luminophor of bis(2,2-bipyridine)-5-amino-1,10-phenanthroline ruthenium(II) [Ru(bpy)2(5-NH2-1,10-phen)(2+)] to form one novel Ru(II) complex, which exhibited significantly enhanced ECL efficiency and stability. Moreover, the carbon nanotubes (CNTs) were employed as nanocarriers for self-enhanced Ru(II) complex loading via ?-? stacking to obtain the coil-like nanocomposite to act as signal probe. Compared with traditional ECL immunoassay, our proposed strategy is simple and sensitive, avoiding the adding of any coreactant into testing solution for signal amplification, and shows a detection limit down to subfemtogram per milliliter level under the optimized experimental condition.
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Target-Triggered Quadratic Amplification for Label-Free and Sensitive Visual Detection of Cytokines Based on Hairpin Aptamer DNAzyme Probes.
Anal. Chem.
PUBLISHED: 12-13-2013
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The employment of DNAzyme probes for visual biodetections has received increasing interest recently due to the simple nature of this type of assay. However, achieving high sensitivity and detecting targets beyond nucleic acids remain two major challenges in DNAzyme-based visual detections. In this work, based on a new quadratic amplification strategy, we developed a sensitive and visual detection method for cytokines by using hairpin aptamer DNAzyme probes. The target cytokine, interferon ? (IFN-?), associates with the aptamer sequences and unfolds the hairpin structure of the probes, leading to simultaneous recycling of the target IFN-? (assisted by Bst-polymerase) and the DNA sequences (aided by ? exonuclease) to achieve quadratic amplification. This quadratic amplification results in the generation of numerous peroxidase-mimicking DNAzymes, which cause significantly intensified color change of the probe solution for highly sensitive detection of IFN-? by the naked eye down to 50 pM. The proposed visual sensing method shows also high selectivity toward the target IFN-? and can be performed in homogeneous solutions with using completely unmodified, synthetic aptamer DNAzyme probes. These distinct advantages of our developed assay protocol make it a potential platform for detecting various types of biomolecules with careful probe designs.
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Cascade signal amplification for ultrasensitive electrochemical DNA detection.
Analyst
PUBLISHED: 10-28-2013
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In this work, by integrating multiple signal enhancement approaches, a new cascade signal amplification strategy is described to achieve highly sensitive electrochemical DNA detection. The presence of the target DNA leads to the unfolding of the biotin-modified hairpin probes on the sensor surface. With the addition of the primer sequences and polymerase, the target DNA is recycled and reused through isothermal strand-displacement polymerase reactions (ISDPR) to unfold a large number of the probes, which offer numerous binding sites to capture alkaline phosphatase (ALP)-loaded nanoparticle labels. These surface captured ALP enzymes catalyze the conversion of p-aminophenylphosphate to p-aminophenol, which generates amplified catalytic current responses due to the redox-recycling process during the potential sweep in the presence of the co-reactant NADH. With the synergistic signal amplifications by ISDPR-assisted target recycling, multi-ALP enzyme labels and redox-recycling, the proposed method offers highly sensitive detection of DNA down to 0.1 fM with single-base discrimination capability. Due to the significantly high sensitivity, the developed cascade signal amplification strategy can be potentially extended to detect various DNA targets at ultralow levels for early diagnoses of different diseases.
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Quadratic recycling amplification for label-free and sensitive visual detection of HIV DNA.
Biosens Bioelectron
PUBLISHED: 10-10-2013
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Visual detections have attracted great research attentions recently due to their convenient monitoring of the target analytes without using any advanced instruments. However, achieving visual detection of trace amounts of biomolecules with PCR-like sensitivity remains a major challenge. In current work, we describe a new quadratic signal amplification strategy for sensitive visual detection of HIV DNA biomarkers based on exonuclease III (Exo III)-assisted DNA recycling amplification and DNAzymes. The presence of the target HIV DNA leads to two independent and simultaneous DNA recycling processes to achieve quadratic signal amplification with the assistance of Exo III. This quadratic signal amplification results in catalytic cleavage of the G-quadruplex sequence-locked hairpin probes to release numerous active G-quadruplex sequences, which further associate with hemin to form DNAzymes and cause significantly intensified color change for sensitive and visual detection of HIV DNA down to 2.5pM. The proposed visual detection method employs un-modified hairpin DNA as probes, avoids using any complex and expensive instruments for signal transduction and is essentially simple. This method also shows single-base mismatch discrimination capability as well. All these features make our developed DNA detection method holds great potential for visual monitoring of various DNA biomarkers at ultralow levels with careful and proper probe designs.
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A highly sensitive electrochemical aptasensor for thrombin detection using functionalized mesoporous silica@multiwalled carbon nanotubes as signal tags and DNAzyme signal amplification.
Analyst
PUBLISHED: 10-01-2013
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In this work, we demonstrated a novel sensitive sandwich-type pseudobienzyme aptasensor for thrombin detection. Greatly amplified sensitivity was based on mesoporous silica-multiwalled carbon nanotube (mSiO2@MWCNT) nanocomposites as enhanced materials and a pseudobienzyme electrocatalytic system. Firstly, the mSiO2@MWCNT nanocomposites not only have good biocompatibility and a suitable microenvironment for stabilizing the aptamer assembly, but also can load large amounts of electron mediator thionine (Thi), platinum nanoparticles (PtNPs) and hemin/G-quadruplex bioelectrocatalytic complex. Moreover, in the presence of H2O2 in an electrolytic cell, the synergistic reaction of PtNPs and hemin/G-quadruplex bioelectrocatalyzed the reduction of H2O2, dramatically amplifying the response signals of electron mediator Thi and improving the sensitivity. Secondly, dendrimer functionalized reduced graphene oxide (PAMAM-rGO) as the biosensor platform enhanced the surface area for the immobilization of abundant primary aptamers as well as facilitated electron transfer from Thi to the electrode, thus amplifying the detection response. Using the above multiple effects, the approach showed a high sensitivity and a wider linearity for the detection of thrombin in the range between 0.0001 nM and 80 nM with a detection limit of 50 fM. This new design avoided the fussy labeling process and the spatial distribution of each sequentially acting enzyme, which provided an ideal candidate for the development of a sensitive and simple bioanalytical platform.
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Dual signal amplification strategy for the fabrication of an ultrasensitive electrochemiluminescenct aptasensor.
Analyst
PUBLISHED: 09-18-2013
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A dual signal amplification strategy was designed to construct a cathodic peroxydisulfate-based electrochemiluminescence (ECL) aptasensor for the ultrasensitive detection of thrombin (TB) as a model analyte. The signal was amplified by the employment of two kinds of co-reactant, (1) in situ generated dissolved O2 from the cascade catalysis of GOD and HRP as co-reactants and (2) intercalation of a new co-reactant into the grooves of the dsDNA polymers based on the hybridization chain reaction (HCR). Femtomolar levels of TB could be detected using the developed aptasensor, with high sensitivity and good stability. Thus the S2O8(2-)-O2 ECL system has great potential for development and application in clinical diagnostics, immunology and biomedical research.
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An electrochemical aptasensor for thrombin detection based on direct electrochemistry of glucose oxidase using a functionalized graphene hybrid for amplification.
Analyst
PUBLISHED: 09-05-2013
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In this work, we reported a new label-free electrochemical aptasensor for highly sensitive detection of thrombin using direct electron transfer of glucose oxidase (GOD) as a redox probe and a gold nanoparticle-polyaniline-graphene (Au-PANI-Gra) hybrid for amplification. The Au-PANI-Gra hybrid with large surface area provided a biocompatible sensing platform for the immobilization of GOD. GOD was encapsulated into the three-dimensional netlike (3-mercaptopropyl)trimethoxysilane (MPTS) to form the MPTS-GOD biocomposite, which not only retained the native functions and properties, but also exhibited tunable porosity, high thermal stability, and chemical inertness. With abundant thiol tail groups on MPTS, MPTS-GOD was able to chemisorb onto the surface of the Au-PANI-Gra modified electrode through the strong affinity of the Au-S bond. The electrochemical signal originated from GOD, avoiding the addition or labeling of other redox mediators. After immobilizing the thiolated thrombin binding aptamer through gold nanoparticles (AuNPs), GOD as a blocking reagent was employed to block the remaining active sites of the AuNPs and avoid the nonspecific adsorption. The proposed method avoided the labeling process of redox probes and increased the amount of electroactive GOD. The concentration of thrombin was monitored based on the decrease of current response through cyclic voltammetry (CV) in 0.1 M PBS (pH 7.4). With the excellent direct electron transfer of double layer GOD membranes, the resulting aptasensor exhibited high sensitivity for detection of thrombin with a wide linear range from 1.0 × 10(-12) to 3.0 × 10(-8) M. The proposed aptasensor also showed good stability, satisfactory reproducibility and high specificity, which provided a promising strategy for electrochemical aptamer-based detection of other biomolecules.
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An electrogenerated chemiluminescence sensor prepared with a graphene/multiwall carbon nanotube/gold nanocluster hybrid for the determination of phenolic compounds.
Analyst
PUBLISHED: 08-16-2013
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A dispersible graphene/multiwall carbon nanotube/gold nanocluster (GP/MWCNTs/AuNCs) hybrid in aqueous solution was prepared in situ, and characterized by transmission electron microscopy (TEM) and ultraviolet-visible (UV-vis) spectroscopy. Based on the fact that phenolic compounds can enhance the electrogenerated chemiluminescence (ECL) signal at the GP/MWCNTs/AuNCs modified glassy carbon electrode in the presence of peroxydisulfate, an ECL sensor was proposed for the determination of phenolic compounds with high sensitivity, good repeatability and stability. Due to its fascinating features, such as good water solubility and excellent stability, the GP/MWCNTs/AuNCs hybrid would offer a suitable catalytic platform for phenolic compounds and provide potential promise for the construction of ECL sensors.
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Naked eye detection of trace cancer biomarkers based on biobarcode and enzyme-assisted DNA recycling hybrid amplifications.
Biosens Bioelectron
PUBLISHED: 08-06-2013
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Naked eye-based detection has received increasing research interest due to the simplicity nature of this type of assay. However, improving the sensitivity of the naked eye detection method for the monitoring of trace amount of target molecules remains a major challenge. Herein, we describe a biobarcode and an enzyme-assisted DNA recycling hybrid amplification strategy for naked eye detection of sub-picomolar carcinoembryonic antigen (CEA), a cancer biomarker. The presence of CEA and the corresponding antibodies results in the formation of immunocomplexes and the capture of the biobarcodes in a microplate. The massive barcode DNAs released from the biobarcodes hybridize with the G-quadruplex inactive hairpin DNA probes and form catalytic nicking sites for N.BstNBI endonuclease, which cleaves the barcode DNA/hairpin partial dsDNA, releases the G-quadruplex active sequences and recycles the barcode DNA. Due to the barcode DNA recycling process, numerous G-quadruplex active sequences are generated and associate with hemin to form peroxidase mimicking enzymes, which convert colorless ABTS(2-) to green color intensified ABTS(•-) to achieve naked eye detection of CEA down to 0.025ngmL(-1) (0.14pM). The naked eye detection strategy reported herein can be applied also to complicated serum sample matrix, making this approach hold great promise for point-of-care diagnostic applications.
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Coupling of background reduction with rolling circle amplification for highly sensitive protein detection via terminal protection of small molecule-linked DNA.
Analyst
PUBLISHED: 08-03-2013
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In this work, by coupling background current reduction with rolling circle amplification (RCA), we describe the development of an ultrasensitive electrochemical sensing method for protein detection based on a small molecule-linked DNA terminal protection strategy. Our detection platform employs a typical streptavidin (STV)-biotin interaction system. Biotin-linked single-stranded DNA (SH-ssDNA-biotin) is self-assembled on a gold electrode to capture the target protein, STV. The binding of STV with the biotin small molecule recognition element protects the SH-ssDNA-biotin against hydrolysis by exonuclease I (Exo I), while the unbound SH-ssDNA-biotin is effectively hydrolyzed and removed from the electrode surface. The bound STV further interacts with long, RCA-amplified biotin DNAs to facilitate the adsorption of numerous electroactive reporters, hexaammineruthenium(III) chloride (RuHex) via electrostatic interactions, which results in significantly amplified signals for the quantitative determination of STV. Moreover, the removal of the unbound SH-ssDNA-biotin probes from the sensing electrode obviates the accumulation of RuHex and leads to a highly minimized background current. The simultaneous RCA signal amplification and background current reduction is expected to significantly enhance the signal-to-noise ratio and to achieve ultrahigh sensitivity. The results reveal that the developed strategy provides a low detection limit of 0.4 pM with high selectivity.
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A pseudo triple-enzyme cascade amplified aptasensor for thrombin detection based on hemin/G-quadruplex as signal label.
Biosens Bioelectron
PUBLISHED: 07-25-2013
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In this work, a pseudo triple-enzyme cascade amplified electrochemical aptasensor based on hemin/G-quadruplex as signal label for thrombin (TB) was constructed and the amplified electrochemical signal was achieved by the corporate catalysis of alcohol dehydrogenase-graphene sheets (ADH-GSs) bionanocomposite and hemin/G-quadruplex, which simultaneously acted as NADH oxidase and HRP-mimicking DNAzyme. Through "sandwich" reaction, hemin/G-quadruplex labeled gold nanoparticles-ADH-GSs bionanocomposite (AuNPs-ADH-GSs) was captured on electrode surface and thus obtained the electrochemical signal. After the addition of ethanol into the electrolytic cell, ADH availably catalyzed the oxidation of ethanol with the reduction of NAD(+) to NADH. Then, hemin/G-quadruplex as NADH oxidase catalyzed the oxidization of NADH, accompanying with the production of H2O2. Simultaneously, hemin/G-quadruplex as HRP-mimicking DNAzyme catalyzed the reduction of the generated H2O2. Such a catalysis strategy greatly promoted the electron transfer of hemin and resulted in the specific enhancement of electrochemical signal. The proposed TB aptasensor achieved a linear range of 1pM-50nM with a detection limit of 0.3pM (defined as S/N=3). In addition, it showed satisfying stability and reproducibility, good specificity and sensitivity, indicating promising application for the detection of various proteins in clinical analysis.
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Electrochemiluminescence of luminol enhanced by the synergetic catalysis of hemin and silver nanoparticles for sensitive protein detection.
Biosens Bioelectron
PUBLISHED: 07-24-2013
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A novel and ultrasensitive electrochemiluminescence (ECL) immunosensor, which was based on the amplifying ECL of luminol by hemin-reduced graphene oxide (hemin-rGO) and Ag nanoparticles (AgNPs) decorated reduced graphene oxide (Ag-rGO), was constructed for the detection of carcinoembryonic antigen (CEA). For this proposed sandwich-type ECL immunosensor, Au nanoparticles electrodeposited (DpAu) onto hemin-rGO (DpAu/hemin-rGO) constructed the base of the immunosensor. DpAu had outstanding electrical conductivity to promote the electron transfer at the electrode interface and had good biocompatibility to load large amounts of primary antibody (Ab1), which provided an excellent platform for this immunosensor. Moreover, AgNPs and glucose oxidase (GOD) functionalized graphene labeled secondary antibody (Ag-rGO-Ab2-GOD) was designed as the signal probe for the sandwiched immunosensor. Not only did the hemin-rGO improve the electron transfer of the electrode surface, but hemin also further amplified the ECL signal of luminol in the presence of hydrogen peroxide (H2O2). With the aid of Ag-rGO-Ab2-GOD, enhanced signal was obtained by in situ generation of H2O2 and catalysis of AgNPs to ECL reaction of the luminol-H2O2 system. The as-prepared ECL immunosensor exhibited excellent analytical property for the detection of CEA in the range from 0.1pgmL(-1) to 160ngmL(-1) with a detection limit of 0.03pgmL(-1) (SN(-1)=3).
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Sandwich-format electrochemiluminescence assays for tumor marker based on PAMAM dendrimer-l-cysteine-hollow gold nanosphere nanocomposites.
Biosens Bioelectron
PUBLISHED: 07-24-2013
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In this work, a novel polyamidoamine (PAMAM) dendrimer-l-cysteine-hollow gold nanospheres nanocomposite was fabricated and used as the promoter for the peroxydisulfate/O2 ECL system to detect the concentration of the tumor marker carcinoembryonic antigen (CEA). Herein, the carboxyl-terminated PAMAM dendrimers were decorated with l-cysteine (l-Cys) by EDC/NHS coupling chemistry. Then, the hollow gold nanospheres (HGNPs) were employed as effective nano-carriers for the assembly of PAMAM-l-Cys via thiols-Au bonding, which was used for further loading of detection antibody (Ab2) to form the PAMAM-l-Cys-HGNPs-Ab2 bioconjugates. In the presence of target CEA, the sandwiched immuno-structure can be formed between the capture anti-CEA antibodies (Ab1), which self-assembled on deposited gold modified electrode, and the Ab2 on the PAMAM-l-Cys-HGNPs, thereby resulting in a proportional increase in ECL response, due to the significant enhancement of PAMAM-l-Cys-HGNPs toward peroxydisulfate/O2 ECL system. As a result, a sandwich ECL assay for CEA detection was developed with excellent sensitivity of a large concentration variation from 20fg/mL to 1.0ng/mL and a detection limit of 6.7fgmL(-1).
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Target-induced charge reduction of aptamers for visual detection of lysozyme based on positively charged gold nanoparticles.
Chem. Commun. (Camb.)
PUBLISHED: 07-22-2013
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Positively charged gold nanoparticles ((+)AuNPs) are electrostatically adsorbed on the negatively charged aptamers and the solution displays a blue color due to the aggregation of the (+)AuNPs, while the binding of the target lysozyme with the aptamers reduces the charge of the aptamers, which stabilizes the (+)AuNPs and the (+)AuNPs solution remains red in color.
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An ultrasensitive electrochemical aptasensor with autonomous assembly of hemin-G-quadruplex DNAzyme nanowires for pseudo triple-enzyme cascade electrocatalytic amplification.
Chem. Commun. (Camb.)
PUBLISHED: 07-16-2013
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We for the first time fabricate a pseudo triple-enzyme cascade electrocatalytic electrochemical aptasensor by using the alcohol dehydrogenase (ADH) as well as the autonomously assembled hemin-G-quadruplex that simultaneously acted as an NADH oxidase and HRP-mimicking DNAzyme.
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An aptasensing platform for simultaneous detection of multiple analytes based on the amplification of exonuclease-catalyzed target recycling and DNA concatemers.
Analyst
PUBLISHED: 07-01-2013
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In the present study, an ultrasensitive electrochemical aptasensor for the simultaneous detection of thrombin (TB) and ochratoxin A (OTA) was fabricated by using exonuclease-catalyzed target recycling and DNA concatemers for signal amplification. The previously hybridized double-stranded DNAs (SH-cTBA/TBA and SH-cOBA/OBA) were self-assembled on a gold electrode. In the presence of targets, the formation of aptamer-target complexes would lead to not only the dissociation of aptamers (TBA and OBA) from the double-stranded DNAs but also the transformation of the complementary DNAs (SH-cTBA and SH-cOBA) into hairpin structures. Subsequently, owing to employment of RecJf exonuclease, which is a single-stranded DNA-specific exonuclease to selectively digest the appointed DNAs (TBA and OBA), the targets could be liberated from the aptamer-target complexes for recycling of the analytes. Thereafter, probe DNAs (T1 and T2) were employed to hybridize with SH-cTBA and SH-cOBA respectively to provide primers for the concatemer reaction. After that, when four auxiliary DNA strands S1, anthraquinone-2-carboxylic acid (AQ)-labeled S2, S3, S4, as well as hemin were introduced, extended dsDNA polymers with lots of AQ moieties and hemin-G-quadruplex complexes could form on the electrode surface. Then, based on the signal of the AQ and hemin-G-quadruplex complex, an electrochemical aptasensor for the simultaneous detection of TB and OTA was successfully fabricated.
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Target-induced structure switching of hairpin aptamers for label-free and sensitive fluorescent detection of ATP via exonuclease-catalyzed target recycling amplification.
Biosens Bioelectron
PUBLISHED: 06-27-2013
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In this work, we described the development of a new label-free, simple and sensitive fluorescent ATP sensing platform based on exonuclease III (Exo III)-catalyzed target recycling (ECTR) amplification and SYBR Green I indicator. The hairpin aptamer probes underwent conformational structure switching and re-configuration in the presence of ATP, which led to catalytic cleavage of the re-configured aptamers by Exo III to release ATP and to initiate the ECTR process. Such ECTR process resulted in the digestion of a significant number of the hairpin aptamer probes, leading to much less intercalation of SYBR Green I to the hairpin stems and drastic suppression of the fluorescence emission for sensitive ATP detection down to the low nanomolar level. Due to the highly specific affinity bindings between aptamers and ATP, the developed method exhibited excellent selectivity toward ATP against other analogous molecules. Besides, our ATP sensing approach used un-modified aptamer probes and could be performed in a "mix-and-detect" fashion in homogenous solutions. All these distinct advantages of the developed method thus made it hold great potential for the development of simple and robust sensing strategies for the detection of other small molecules.
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What is Visualize?

JoVE Visualize is a tool created to match the last 5 years of PubMed publications to methods in JoVE's video library.

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We use abstracts found on PubMed and match them to JoVE videos to create a list of 10 to 30 related methods videos.

Video X seems to be unrelated to Abstract Y...

In developing our video relationships, we compare around 5 million PubMed articles to our library of over 4,500 methods videos. In some cases the language used in the PubMed abstracts makes matching that content to a JoVE video difficult. In other cases, there happens not to be any content in our video library that is relevant to the topic of a given abstract. In these cases, our algorithms are trying their best to display videos with relevant content, which can sometimes result in matched videos with only a slight relation.