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Find video protocols related to scientific articles indexed in Pubmed.
In vitro PAMAM, phosphorus and viologen-phosphorus dendrimers prevent rotenone-induced cell damage.
Int J Pharm
PUBLISHED: 08-07-2014
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We have investigated whether polyamidoamine (PAMAM), phosphorus (pd) and viologen-phosphorus (vpd) dendrimers can prevent damage to embryonic mouse hippocampal cells (mHippoE-18) caused by rotenone, which is used as a pesticide, insecticide, and as a nonselective piscicide, that works by interfering with the electron transport chain in mitochondria. Several basic aspects, such as cell viability, production of reactive oxygen species and changes in mitochondrial transmembrane potential, were analyzed. mHippoE-18 cells were treated with these structurally different dendrimers at 0.1?M. A 1h incubation with dendrimers was followed by the addition of rotenone at 1?M, and a further 24h incubation. PAMAM, phosphorus and viologen-phosphorus dendrimers all increased cell viability (reduced cell death-data need to be compared with untreated controls). A lower level of reactive oxygen species and a favorable effect on mitochondrial system were found with PAMAM and viologen-phosphorus dendrimers. These results indicate reduced toxicity in the presence of dendrimers.
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Interference of cationic polymeric nanoparticles with clinical chemistry tests--clinical relevance.
Int J Pharm
PUBLISHED: 06-18-2014
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The development of medical nanosystems requires knowledge of their behavior in vivo. Clinical chemistry tests are widely used to estimate the systemic toxicity of nanoparticles. In this paper we have explored the impact of small positively charged nanoparticles-poly(amidoamine), phosphorous and carbosilane dendrimers - on biochemical parameters of standardized serum in vitro. All the dendrimers could shift the main biochemical parameters. Thus, in the case of patients having the normal, but 'boundary', values of biochemical parameters, nanoparticle-induced changes can be wrongly interpreted as evidence of some dysfunctions (hepatic, renal, etc.). Moreover, the effects of nanoparticles of metals, carbon nanotubes, quantum dots, fullerenes, dendrimers having been sized up to 4000 nm and the hundreds of reactive groups, can be significantly higher. Thus, preliminary evaluation of any nanomaterial in vitro is required in clinical chemistry tests before its application in vivo to draw the correct conclusions and benefit animals.
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Aligned collagen-GAG matrix as a 3D substrate for Schwann cell migration and dendrimer-based gene delivery.
J Mater Sci Mater Med
PUBLISHED: 04-21-2014
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The development of artificial off-the-shelf conduits that facilitate effective nerve regeneration and recovery after repair of traumatic nerve injury gaps is of fundamental importance. Collagen-glycosaminoglycan (GAG) matrix mimicking Schwann cell (SC) basal lamina has been proposed as a suitable and biologically rational substrate for nerve regeneration. In the present study, we have focused on the permissiveness of this matrix type for SC migration and repopulation, as these events play an essential role in nerve remodeling. We have also demonstrated that SCs cultured within collagen-GAG matrix are compatible with non-viral dendrimer-based gene delivery, that may allow conditioning of matrix-embedded cells for future gene therapy applications.
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The influence of heterocyclic compound-PAMAM dendrimer complexes on evoked electrical responses in slices of hypoxic brain tissue.
Cell. Mol. Biol. Lett.
PUBLISHED: 04-11-2014
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We used complexes between a fourth generation polyamidoamine (PAMAM) dendrimer and one of two heterocyclic compounds - 1-(6-hydroxyhexyl)-3-(5-phenyl-isoxazole-3-yl)-urea or 5-phenyl-isoxazole-3-carboxylic acid - to reduce oxygen consumption in transverse slices of the hippocampus taken from 4-week old male rats. In vitro electrophysiological experiments revealed that the inhibitory effect of the hypoxic state on the evoked responses was enhanced in the presence of the complexes. The data were analyzed in terms of the potential antitumor effects of these complexes.
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The effect of near-infrared MLS laser radiation on cell membrane structure and radical generation.
Lasers Med Sci
PUBLISHED: 03-30-2014
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The therapeutic effects of low-power laser radiation of different wavelengths and light doses are well known, but the biochemical mechanism of the interaction of laser light with living cells is not fully understood. We have investigated the effect of MLS (Multiwave Locked System) laser near-infrared irradiation on cell membrane structure, functional properties, and free radical generation using human red blood cells and breast cancer MCF-4 cells. The cells were irradiated with low-intensity MLS near-infrared (simultaneously 808 nm, continuous emission and 905 nm, pulse emission, pulse-wave frequency, 1,000 or 2,000 Hz) laser light at light doses from 0 to 15 J (average power density 212.5 mW/cm(2), spot size was 3.18 cm(2)) at 22 °C, the activity membrane bound acetylcholinesterase, cell stability, anti-oxidative activity, and free radical generation were the parameters used in characterizing the structural and functional changes of the cell. Near-infrared low-intensity laser radiation changed the acetylcholinesterase activity of the red blood cell membrane in a dose-dependent manner: There was a considerable increase of maximal enzymatic rate and Michaelis constant due to changes in the membrane structure. Integral parameters such as erythrocyte stability, membrane lipid peroxidation, or methemoglobin levels remained unchanged. Anti-oxidative capacity of the red blood cells increased after MLS laser irradiation. This irradiation induced a time-dependent increase in free radical generation in MCF-4 cells. Low-intensity near-infrared MLS laser radiation induces free radical generation and changes enzymatic and anti-oxidative activities of cellular components. Free radical generation may be the mechanism of the biomodulative effect of laser radiation.
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Oleochemical-tethered SBA-15-type silicates with tunable nanoscopic order, carboxylic surface, and hydrophobic framework: cellular toxicity, hemolysis, and antibacterial activity.
Chemistry
PUBLISHED: 03-12-2014
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Novel silicates were prepared by using silylated natural fatty acids (derived from triglyceride renewable oils) as co-condensing reagents in presence of tetraethyl orthosilicate (TEOS) and the triblock copolymer, pluronic P123, as a structure directing agent. A series of carboxylic acid functionalized SBA-15-type mesoporous silicates were obtained with tunable nanoscopic order and reactive functional groups that allow the conjugation of amino probes by peptide coupling. Photophysical studies of the covalently linked aminopyrene substantiated that the internal framework of these materials have pronounced hydrophobicity. Moreover, phase separation that can emanate from the bulkiness of the starting fatty silanes has been ruled out owing to the absence of excimers after aminopyrene grafting. The hemotoxicity, cytotoxicity, and antimicrobial activity of these novel silicates were then evaluated. Without discrimination, the functionalized silicates show a significant decrease of red blood cell hemolysis as compared to bare SBA-15-silica material. Within the modified silicate series, germanium-free mesoporous silicates induce only a slight decrease in cell viability and, more interestingly, they exhibit negligible hemolytic effect. Moreover, increasing their concentration in the medium reduces the concentration of released hemoglobin as a result of Hb adsorption. Promising antimicrobial properties were also observed for these silicates with a slight dependency on whether phenylgermanium fragments were present within the silicate framework.
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How to study dendrimers and dendriplexes III. Biodistribution, pharmacokinetics and toxicity in vivo.
J Control Release
PUBLISHED: 01-30-2014
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This paper reviews the biodistribution, toxicity and pharmacokinetics of pure dendrimers and their complexes with nucleic acids (dendriplexes) in animals, including mice, rats, rabbits, and guinea pigs. Methods and results will both be discussed. The paradigm about dendrimers' toxicity based on in vitro studies should be revised; almost all dendrimers of low and middle generations are non-toxic in vivo, despite showing some cytotoxic effects in vitro. Only the high generations of unmodified cationic dendrimers in high doses have some toxicity in vivo. Modifications of dendrimers decrease their toxicity, even when this has already been acceptable with regard to unmodified dendrimers. Several undesirable effects following administration of unmodified cationic dendrimers diminish during prolonged dosing because of the development of counteracting mechanisms. Disturbances tend to return to normal levels during the recovery period after dendrimers have ceased to be administered to animals. Neutralization of the surface charge of dendrimers in their dendriplexes leads to less toxicity in vivo. Although dendrimers and dendriplexes accumulate temporarily in liver, pancreas, heart, and kidneys, they do not do permanent damage to them, i.e. the risk of irreversible damage or malfunction of these internal organs is slight. Chemical modifications of dendrimers determine the desired location of multifunctional dendrimer-based conjugates and dendriplexes in a targeted organ. Clearance of dendrimers also strongly depends on their chemical structure. When nucleic acids are complexed with dendrimers (forming so-called dendriplexes), they are more stable, having longer circulation times than free and PEI-complexed ones. Dendrimers are highly efficient in transfection and can be targeted to any organ, e.g. brain, lung and kidneys. The vast majority of dendrimers and dendriplexes are non-immunogenic. To sum up, these promising results from in vivo studies open up the possibility of dendrimers being applied as a new generation of nano-therapeutic agents in medicine, especially in human gene therapy.
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Formation of complexes between PAMAM-NH2 G4 dendrimer and L-?-tryptophan and L-?-tyrosine in water.
Spectrochim Acta A Mol Biomol Spectrosc
PUBLISHED: 01-29-2014
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Interactions between electromagnetic radiation and the side substituents of aromatic amino acids are widely used in the biochemical studies on proteins and their interactions with ligand molecules. That is why the aim of our study was to characterize the formation of complexes between PAMAM-NH2 G4 dendrimer and L-?-tryptophan and L-?-tyrosine in water. The number of L-?-tryptophan and L-?-tyrosine molecules attached to the macromolecule of PAMAM-NH2 G4 dendrimer and the formation constants of the supramolecular complexes formed have been determined. The macromolecule of PAMAM-NH2 G4 can reversibly attach about 25 L-?-tryptophan molecules with equilibrium constant K equal to 130±30 and 24±6 L-?-tyrosine molecules. This characterization was deduced on the basis of the solubility measurements of the amino acids in aqueous dendrimer solutions, the (1)H NMR and 2D-NOESY measurements of the dendrimer solutions with the amino acids, the equilibrium dialysis and the circular dichroism measurements of the dendrimer aqueous solutions with L-?-tryptophan. Our date confirmed the interactions of L-?-tryptophan and L-?-tyrosine with the dendrimer in aqueous solution and indicated a reversible character of the formed complexes.
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Stabilizing effect of small concentrations of PAMAM dendrimers at the insulin aggregation.
Colloids Surf B Biointerfaces
PUBLISHED: 01-28-2014
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Dendrimers' action on proteins and peptides has a dual and controversial character. On one hand, they dissolve prion protein and amyloid fibrils aggregates, which are otherwise only soluble in solvents containing both detergents and high denaturant concentrations. On the other hand they are able to destabilize proteins in generation dependent manner. In present work we estimated the influence of small concentrations (up to 1.4 ?g/ml) of cationic, neutral and anionic poly(amidoamine) dendrimers of 3rd and 4th generations on dithiotreitol induced aggregation of insulin. It was found that cationic dendrimers decreased the insulin aggregation, while anionic and neutral ones did not. At the same time, destabilizing effect of dendrimers on insulin structure was not observed. The conclusion was made that small concentrations of dendrimers can be applied to prevent or decrease the formation of misfolded structures of protein.
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Toxicity and proapoptotic activity of poly(propylene imine) glycodendrimers in vitro: Considering their contrary potential as biocompatible entity and drug molecule in cancer.
Int J Pharm
PUBLISHED: 11-15-2013
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Since the first dendrimers were synthesized, scientists around the world have studied their properties and potential applications. Cationic dendrimers are characterized by significant toxicity due to their interactions with cells components. The replacement of all cationic surface groups by neutral ones and therefore diminishing positive charge reduces the toxicity but may also lead to loss of dendrimers desirable properties and restrict their biomedical applications. We have compared the cytotoxicity, as well as proapoptotic and antiproliferative activity of unmodified fourth generation PPI dendrimer (PPI-G4) and dendrimers modified with maltose (Mal) or maltotriose (Mal-III) - for full (dense shell - DS) or partial (open shell - OS) surface modifications. We have proved that among glycodendrimers, the OS-Mal PPI-G4 dendrimer is the most toxic, whereas DS-Mal-III molecule shows relatively weak or even no effect. We have also confirmed that OS dendrimers, both maltotriose and maltose modified, not only reduce cancer cells viability by inducing apoptosis but also inhibit their proliferation. The use of dendrimers as an active substance, which may be a drug per se is one of the most exciting and clinically important applications of cancer nanotechnology, therefore a partial modification of the surface appears to be a perfect solution for this purpose.
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Poly(amidoamine) dendrimer complexes as a platform for gene delivery.
Expert Opin Drug Deliv
PUBLISHED: 10-30-2013
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Introduction: Gene therapy is one of the most effective ways to treat major infectious diseases, cancer and genetic disorders. It is based on several viral and non-viral systems for nucleic acid delivery. The number of clinical trials based on application of non-viral drug and gene delivery systems is rapidly increasing. Areas covered: This review discusses and summarizes recent advances in poly(amidoamine) dendrimers as effective gene carriers in vitro and in vivo, and their advantages and disadvantages relative to viral vectors and other non-viral systems (liposomes, linear polymers) are considered. Expert opinion: In this regard, dendrimers are non-immunogenic and have the highest efficiency of transfection among other non-viral systems, and none of the drawbacks characteristic for viral systems. The toxicity of dendrimers both in vitro and in vivo is an important question that has been addressed on many occasions. Several non-toxic and efficient multifunctional dendrimer-based conjugates for gene delivery, along with modifications to improve transfection efficiency while decreasing cytotoxicity, are discussed. Twelve paradigms that affected the development of dendrimer-based gene delivery are described. The conclusion is that dendrimers are promising candidates for gene delivery, but this is just the beginning and further studies are required before using them in human gene therapy.
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Promising low-toxicity of viologen-phosphorus dendrimers against embryonic mouse hippocampal cells.
Molecules
PUBLISHED: 08-12-2013
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A new class of viologen-phosphorus dendrimers (VPDs) has been recently shown to possess the ability to inhibit neurodegenerative processes in vitro. Nevertheless, in the Central Nervous Systems domain, there is little information on their impact on cell functions, especially on neuronal cells. In this work, we examined the influence of two VPD (VPD1 and VPD3) of zero generation (G0) on murine hippocampal cell line (named mHippoE-18). Extended analyses of cell responses to these nanomolecules comprised cytotoxicity test, reactive oxygen species (ROS) generation studies, mitochondrial membrane potential (??m) assay, cell death detection, cell morphology assessment, cell cycle studies, as well as measurements of catalase (CAT) activity and glutathione (GSH) level. The results indicate that VPD1 is more toxic than VPD3. However, these two tested dendrimers did not cause a strong cellular response, and induced a low level of apoptosis. Interestingly, VPD1 and VPD3 treatment led to a small decline in ROS level compared to untreated cells, which correlated with slightly increased catalase activity. This result indicates that the VPDs can indirectly lower the level of ROS in cells. Summarising, low-cytotoxicity on mHippoE-18 cells together with their ability to quench ROS, make the VPDs very promising nanodevices for future applications in the biomedical field as nanocarriers and/or drugs per se.
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Mechanism of Cationic Phosphorus Dendrimer Toxicity against Murine Neural Cell Lines.
Mol. Pharm.
PUBLISHED: 07-30-2013
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The purpose of this manuscript is to study the toxic responses against murine embryonic hippocampal cells (mHippoE-18) and neuroblastoma cells (N2a) to treatment with cationic phosphorus dendrimers (CPD). Two low generations of CPD-generation 2 (G2) and generation 3 (G3)-were applied to cell cultures to monitor events leading to either apoptosis or necrosis. These processes were analyzed using several bioassays, which included the detection of reactive oxygen species (ROS), mitochondrial membrane potential (??m) alterations, morphology changes, apoptotic and dead cells, cytochrome c (Cyt c) release, caspase 3 activity, DNA fragmentation, as well as changes in cell cycle phases distribution. The results showed that CPD became highly cytotoxic at concentrations above 1 ?M and at 0.7 ?M in the case of G3 for mHippoE-18 cells. The toxicity was manifested by a pronounced decrease in cell viability, which is correlated with disturbances in cellular activities, such as massive ROS generation. The breakdown of cellular processes leads mainly to the necrotic cell death. Our findings are of high importance in the context of further biomedical studies on CPD.
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Influence of MLS laser radiation on erythrocyte membrane fluidity and secondary structure of human serum albumin.
Mol. Cell. Biochem.
PUBLISHED: 07-14-2013
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The biostimulating activity of low level laser radiation of various wavelengths and energy doses is widely documented in the literature, but the mechanisms of the intracellular reactions involved are not precisely known. The aim of this paper is to evaluate the influence of low level laser radiation from an multiwave locked system (MLS) of two wavelengths (wavelength = 808 nm in continuous emission and 905 nm in pulsed emission) on the human erythrocyte membrane and on the secondary structure of human serum albumin (HSA). Human erythrocytes membranes and HSA were irradiated with laser light of low intensity with surface energy density ranging from 0.46 to 4.9 J cm(-2) and surface energy power density 195 mW cm(-2) (1,000 Hz) and 230 mW cm(-2) (2,000 Hz). Structural and functional changes in the erythrocyte membrane were characterized by its fluidity, while changes in the protein were monitored by its secondary structure. Dose-dependent changes in erythrocyte membrane fluidity were induced by near-infrared laser radiation. Slight changes in the secondary structure of HSA were also noted. MLS laser radiation influences the structure and function of the human erythrocyte membrane resulting in a change in fluidity.
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Doxycycline-regulated GDNF expression promotes axonal regeneration and functional recovery in transected peripheral nerve.
J Control Release
PUBLISHED: 07-09-2013
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Increased production of neurotrophic factors (NTFs) is one of the key responses seen following peripheral nerve injury, making them an attractive choice for pro-regenerative gene therapies. However, the downside of over-expression of certain NTFs, including glial cell line-derived neurotrophic factor (GDNF), was earlier found to be the trapping and misdirection of regenerating axons, the so-called candy-store effect. We report a proof-of-principle study on the application of conditional GDNF expression system in injured peripheral nerve. We engineered Schwann cells (SCs) using dendrimers or lentiviral transduction with the vector providing doxycycline-regulated GDNF expression. Injection of GDNF-modified cells into the injured peripheral nerve followed by time-restricted administration of doxycycline demonstrated that GDNF expression in SCs can also be controlled locally in the peripheral nerves of the experimental animals. Cell-based GDNF therapy was shown to increase the extent of axonal regeneration, while controlled deactivation of GDNF effectively prevented trapping of regenerating axons in GDNF-enriched areas, and was associated with improved functional recovery.
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Interaction between polyamidoamine (PAMAM) dendrimers and bovine insulin.
Neuro Endocrinol. Lett.
PUBLISHED: 06-19-2013
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In this study the mechanism of interactions between polyamidoamine (PAMAM) dendrimers and bovine insulin was examined. The insulin is a 51 amino acid peptide-hormone involved in the homeostasis of blood glucose levels. This molecule consists of two chains - A and B - linked by two disulphide bridges. As insulin contains four tyrosine residues it was possible to evaluate dendrimers effect on protein conformation by measuring changes in the fluorescence spectra of insulin after addition of dendrimers or classical quenchers.
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Viologen-phosphorus dendrimers exhibit minor toxicity against a murine neuroblastoma cell line.
Cell. Mol. Biol. Lett.
PUBLISHED: 06-04-2013
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Dendrimers containing viologen (derivatives of 4,4-bipyridyl) units in their structure have been demonstrated to exhibit antiviral activity against human immunodeficiency virus (HIV-1). It has also recently been revealed that novel dendrimers with both viologen units and phosphorus groups in their structure show different antimicrobial, cytotoxic and hemotoxic properties, and have the ability to influence the activity of cholinesterases and to inhibit ?-synuclein fibrillation. Since the influence of viologen-phosphorus structures on basic cellular processes had not been investigated, we examined the impact of such macromolecules on the murine neuroblastoma cell line (N2a). We selected three water-soluble viologen-phosphorus (VPD) dendrimers, which differ in their core structure, number of viologen units and number and type of surface groups, and analyzed several aspects of the cellular response. These included cell viability, generation of reactive oxygen species (ROS), alterations in mitochondrial activity, morphological modifications, and the induction of apoptosis and necrosis. The MTT assay results suggest that all of the tested dendrimers are only slightly cytotoxic. Although some changes in ROS formation and mitochondrial function were detected, the three compounds did not induce apoptosis or necrosis. In light of these results, we can assume that the tested VPD are relatively safe for mouse neuroblastoma cells. Although more research on their safety is needed, VPD seem to be promising nanoparticles for further biomedical investigation.
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The influence of maltotriose-modified poly(propylene imine) dendrimers on the chronic lymphocytic leukemia cells in vitro: dense shell G4 PPI.
Mol. Pharm.
PUBLISHED: 05-16-2013
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Chronic lymphocytic leukemia (CLL) is the most common leukemia in Europe and North America. For many years scientists and doctors have been working on introducing the most effective therapy into CLL as prognosis of survival time and the course of the disease differ among patients, which might pose a problem in treating. Nanotechnology is providing new insights into diagnosis and, compared with conventional treatments, more efficient treatments, which might improve patients comfort by decreasing side effects. Among the various nanoparticles that are available, dendrimers are one of the most promising. The aim of this study was a preliminary assessment of the clinical value of treating CLL patients with fourth generation poly(propylene imine) (PPI) dendrimers-either unmodified (PPI-G4) or approximately 90% maltotriose-modified (PPI-G4-DS-Mal-III). PPI-G4-DS-Mal-III dendrimers have, in contrast to the cationic PPI-G4, a neutral surface charge and are characterized by low cyto-, geno-, and hematotoxicity in vitro and in vivo. For the in vitro study we used blood mononuclear cells collected from both untreated CLL patients and from healthy donors. Apoptosis was measured by an annexin-V (Ann-V)/propidium iodide (IP) assay, and mitochondrial membrane potential was estimated with use of Mito Tracker Red CMXRos. Presented results confirm the influence of dendrimers PPI-G4 and PPI-G4-DS-Mal-III on apoptosis and CLL lymphocytes viability in in vitro cultures. Both tested dendrimers demonstrated higher cytotoxicity to CLL cells than to healthy donors cells, whereas unmodified dendrimers were more hematotoxic. The surface modification clearly makes glycodendrimers much more suitable for biomedical applications than unmodified PPI-G4; therefore further biological evaluations of these nanoparticles are conducted in our laboratories.
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Interaction of cationic carbosilane dendrimers and their complexes with siRNA with erythrocytes and red blood cell ghosts.
Biochim. Biophys. Acta
PUBLISHED: 04-30-2013
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We have investigated the interactions between cationic NN16 and BDBR0011 carbosilane dendrimers with red blood cells or their cell membranes. The carbosilane dendrimers used possess 16 cationic functional groups. Both the dendrimers are made of water-stable carbon-silicon bonds, but NN16 possesses some oxygen-silicon bonds that are unstable in water. The nucleic acid used in the experiments was targeted against GAG-1 gene from the human immunodeficiency virus, HIV-1. By binding to the outer leaflet of the membrane, carbosilane dendrimers decreased the fluidity of the hydrophilic part of the membrane but increased the fluidity of the hydrophobic interior. They induced hemolysis, but did not change the morphology of the cells. Increasing concentrations of dendrimers induced erythrocyte aggregation. Binding of short interfering ribonucleic acid (siRNA) to a dendrimer molecule decreased the availability of cationic groups and diminished their cytotoxicity. siRNA-dendrimer complexes changed neither the fluidity of biological membranes nor caused cell hemolysis. Addition of dendriplexes to red blood cell suspension induced echinocyte formation.
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Contribution of hydrophobicity, DNA and proteins to the cytotoxicity of cationic PAMAM dendrimers.
Int J Pharm
PUBLISHED: 04-22-2013
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In most articles, cytotoxicity of cationic polyamidoamine (PAMAM) dendrimers toward red blood cells has been exclusively explained by their surface charge. We have focused on dendrimer hydrophobicity as a second possible factor that determines this cytotoxicity. Using PAMAM-NH2 dendrimers from the 3rd to the 6th generations and PAMAM-NH2-C12(25%) dendrimer of the 4th generation bearing 25% acyl groups, these induced hemolysis that increased with their surface charge and hydrophobicity. Interaction of PAMAM-NH2-C12(25%) G4 dendrimer with blood proteins (?-globulin, ?-thrombin, human serum albumin) and calf thymus DNA (ctDNA) significantly reduced their cytotoxicity toward red blood cells.
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The influence of PAMAM dendrimers surface groups on their interaction with porcine pepsin.
Biochim. Biophys. Acta
PUBLISHED: 03-20-2013
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In this study the ability of three polyamidoamine (PAMAM) dendrimers with different surface charge (positive, neutral and negative) to interact with a negatively charged protein (porcine pepsin) was examined. It was shown that the dendrimer with a positively charged surface (G4 PAMAM-NH2), as well as the dendrimer with a neutral surface (G4 PAMAM-OH), were able to inhibit enzymatic activity of pepsin. It was also found that these dendrimers act as mixed partially non-competitive pepsin inhibitors. The negatively charged dendrimer (G3.5 PAMAM-COOH) was not able to inhibit the enzymatic activity of pepsin, probably due to the electrostatic repulsion between this dendrimer and the protein. No correlation between changes in enzymatic activity of pepsin and alterations in CD spectrum of the protein was observed. It indicates that the interactions between dendrimers and porcine pepsin are complex, multidirectional and not dependent only on disturbances of the secondary structure.
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Phosphorus dendrimers as carriers of siRNA--characterisation of dendriplexes.
Molecules
PUBLISHED: 03-18-2013
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There are many types of dendrimers used as nanomolecules for gene delivery but there is still an ongoing search for ones that are able to effectively deliver drugs to cells. The possibility of gene silencing using siRNA gives hope for effective treatment of numerous diseases. The aim of this work was to investigate in vitro biophysical properties of dendriplexes formed by siRNA and cationic phosphorus dendrimers of 3rd and 4th generation. First, using the ethidium bromide intercalation method, it was examined whether dendrimers have an ability to form complexes with siRNA. Next, the characterisation of dendriplexes formed at different molar ratios was carried out using biophysical methods. The effects of zeta potential, size and changes of siRNA conformation on the complexation with dendrimers were examined. It was found that both phosphorus dendrimers interacted with siRNA. The zeta potential values of dendriplexes ranged from negative to positive and the hydrodynamic diameter depended on the number of dendrimer molecules in the complex. Furthermore, using circular dichroism spectroscopy it was found that cationic phosphorus dendrimers changed only slightly the shape of siRNA CD spectra, thus they did not induce significant changes in the nucleic acid secondary structure during complex formation.
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Viologen-Phosphorus Dendrimers Inhibit ?-Synuclein Fibrillation.
Mol. Pharm.
PUBLISHED: 02-19-2013
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Inhibition of ?-synuclein (ASN) fibril formation is a potential therapeutic strategy in Parkinsons disease and other synucleinopathies. The aim of this study was to examine the role of viologen-phosphorus dendrimers in the ?-synuclein fibrillation process and to assess the structural changes in ?-synuclein under the influence of dendrimers. ASN interactions with phosphonate and pegylated surface-reactive viologen-phosphorus dendrimers were examined by measuring the zeta potential, which allowed determining the number of dendrimer molecules that bind to the ASN molecule. The fibrillation kinetics and the structural changes were examined using ThT fluorescence and CD spectroscopy. Depending on the concentration of the used dendrimer and the nature of the reactive groups located on the surface, ASN fibrillation kinetics can be significantly reduced, and even, in the specific case of phosphonate dendrimers, the fibrillation can be totally inhibited at low concentrations. The presented results indicate that viologen-phosphorus dendrimers are able to inhibit ASN fibril formation and may be used as fibrillar regulating agents in neurodegenerative disorders.
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HIV-Antigens Charged on Phosphorus Dendrimers as Tools for Tolerogenic Dendritic Cells-Based Immunotherapy.
Curr. Med. Chem.
PUBLISHED: 02-11-2013
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Aims: The objective was to study if cationic phosphorus dendrimers can be used as DC-based vaccine or adjuvant in anti-HIV-1 vaccine development when associated with HIV-1 derived peptides. Materials & Methods: The HIV-derived peptides uptake in DC and the phenotype of iDC and mDC were studied using Flow Cytometry analysis. Migration of mDC was evaluated by an in vitro chemotaxis assay. Allogenic T-cells proliferative response induced by DC was studied using Flow Cytometry assays. Cytokines production was analysed by Diaclon DIAplex Th1/Th2/Inflammation kit. Results: All phosphorus dendrimers showed the ability to deliver HIV-derived peptides in DC. The phosphorus dendrimers from second and third generations induced important changes in phenotype. Moreover, the treatment of mDC with the second generation dendrimer and derivated dendriplexes modified cellular migratory properties, altered their capacity to stimulate allogenic naïve T cells in vitro and impeded the production of pro-inflammatory cytokines. Conclusions: The phosphorus dendrimers cannot be used as vaccines because they would not have the ability to induce an immune response. The cationic phosphorus dendrimers associated with HIV-derived peptides have the ability to deliver peptides as non-viral vectors. However, there are other potential therapeutic applications of these compounds, for instance as topical anti-inflammatory agents, as compounds for allograft rejection or autoimmune diseases and as agents inducing specific tolerance with antigen-loaded DC against allergy reaction. Nevertheless, these applications need to be evaluated.
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Modified PAMAM dendrimer with 4-carbomethoxypyrrolidone surface groups reveals negligible toxicity against three rodent cell-lines.
Nanomedicine
PUBLISHED: 01-30-2013
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Modification of the surface groups of dendrimers is one of the methods to improve their biocompatibility. This article presents results of experiments related to the toxicity of a modified polyamidoamine (PAMAM) dendrimer of the fourth generation with 4-carbomethoxypyrrolidone surface groups (PAMAM-pyrrolidone dendrimer). The cytotoxic activity of the dendrimer was tested on Chinese hamster fibroblasts (B14), embryonic mouse hippocampal cells (mHippoE-18) and rat liver derived cells (BRL-3A). The same cell lines were used to investigate the influence of pyrrolidone dendrimer on the mitochondrial membrane potential, intracellular ROS level and its ability to induce apoptosis or necrosis. The analyzed dendrimer showed only minor toxicity and no ability to induce apoptosis. The most important finding is the lack of influence of the PAMAM-pyrrolidone dendrimer on intracellular ROS level and mitochondrial membrane potential.
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Novel Si-C carbosilane dendrimers as carriers for anti-HIV nucleic acids: studies on complexation and interaction with blood cells.
Colloids Surf B Biointerfaces
PUBLISHED: 01-16-2013
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Treatment of HIV infection by gene therapy is a promising tool for combating AIDS. One of the primary limitations of gene therapy is the effective delivery of nucleic acids to the target cells. Dendrimers are nanoparticles that are increasingly being used as nucleic acid vehicles. We have synthesized "Si-C" amino-terminated carbosilane dendrimers [GnO3(NMe3)m](m+) functionalized with quaternary ammonium (NMe3(+)) terminal groups via hydrosilylation of allyl dimethylamine with the corresponding GnO3(SiH)m dendrimers and further addition of MeI. These dendrimers are soluble in water. Initially, complexation between these "Si-C" dendrimers and anti-HIV nucleic acids (oligodeoxynucleotides ANTITAR and GEM91, siRNA siP24) was studied and molar ratios for complete complexation were determined. Then the charge and size of the dendriplexes (complexes of "Si-C" dendrimers with nucleic acids) were analyzed and it was found that they possessed charges of +5 to +40 mV and sizes of 60-600 nm (zeta-size) or 50-100 nm (atomic force microscopy) suitable for cell transfection. Stability studies showed that the dendriplexes were stable over time and were resistant to degradation by serum albumin. The effects of dendrimers and their dendriplexes on erythrocytes (isolated and in whole blood) revealed that the dendriplexes were significantly less cytotoxic than the pure dendrimers. The effects of dendrimers and their dendriplexes on peripheral blood mononuclear cells (the main target of HIV) were analyzed and it was found that the dendriplexes were 10 times less cytotoxic than the pure dendrimers. Finally, transfection experiments revealed that "Si-C"-carbosilane dendrimers had a restricted ability to deliver long-chain double-stranded nucleic acids. The results indicate that these cationic carbosilane dendrimers are good candidates for delivering short-chain siRNA and oligodeoxynucleotide to HIV-infected peripheral blood mononuclear cells or lymphocytes.
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Non-virally modified human mesenchymal stem cells produce ciliary neurotrophic factor in biodegradable fibrin-based 3D scaffolds.
J Pharm Sci
PUBLISHED: 10-26-2011
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We report the adaptation of dendrimer-based nonviral expression system for ciliary neurotrophic factor (CNTF) overproduction in human mesenchymal stem cells (hMSCs) embedded into fibrin-based three-dimensional (3D) matrix. Time-restricted neurotrophin expression enables autologous adult stem cells for additional trophic support and increases their therapeutic potential in neuroregeneration applications. Polyamidoamine (PAMAM)-NH(2) dendrimers of fourth generation effectively provided virus-free delivery and expression of CNTF-internal ribosome entry site-green fluorescent protein cassette with a transfection efficiency in hMSCs over 11%. CNTF levels in transfected cultures were 10-fold higher as compared with the control cells. Dendrimer-driven CNTF expression also persisted in hMSCs embedded into fibrin-based 3D matrix, an emerging vehicle for cell delivery or bioartificial organ formation. Nonviral modification of autologous adult stem cells with use of dendrimers is a novel tool perspective in terms of biosafety and technological availability.
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Influence of dendrimers on red blood cells.
Cell. Mol. Biol. Lett.
PUBLISHED: 06-29-2011
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Dendrimers, highly branched macromolecules with a specific size and shape, provide many exciting opportunities for biomedical applications. However, most dendrimers demonstrate toxic and haemolytic activity because of their positively charged surface. Masking the peripheral cationic groups by coating them with biocompatible molecules is a method to reduce it. It was proven that modified dendrimers can even diminish haemolytic activity of encapsulated drugs. Experiments confirmed that anionic dendrimers are less haemotoxic than cationic ones. Due to the high affinity of dendrimers for serum proteins, presence of these components in an incubation buffer might also influence red blood cell (RBC)-dendrimer interactions and decrease the haemolysis level. Generally, haemotoxicity of dendrimers is concentration-, generation-, and time-dependent. Various changes in the RBCs shape in response to interactions with dendrimers have been observed, from echinocytic transformations through cell aggregation to cluster formation, depending on the dendrimers type and concentration. Understanding the physical and chemical origins of dendrimers influences on RBCs might advance scientists ability to construct dendrimers more suitable for medical applications.
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Effect of phosphorus dendrimers on DMPC lipid membranes.
Chem. Phys. Lipids
PUBLISHED: 06-07-2011
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Large unilamellar liposomes and multilamellar vesicles consisting of DMPC interacted with cationic phosphorus-containing dendrimers CPDs G3 and G4. DSC and ?-potential measurements have shown that liposomal-dendrimeric molecular recognition probably occurs due to the interaction between the complementary surface groups. Calorimetric studies indicate that the enthalpy of the transition of the lipids that interact with CPDs is dependent on the dendrimers generation. These results can be used in order to rationally design mixed modulatory liposomal locked-in dendrimeric, drug delivery nano systems.
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The influence of PAMAM-OH dendrimers on the activity of human erythrocytes ATPases.
Biochim. Biophys. Acta
PUBLISHED: 05-10-2011
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Dendrimers are a relatively new and still not fully examined group of polybranched polymers. In this study polyamidoamine dendrimers with hydroxyl surface groups (PAMAM-OH) of third, fourth and fifth generation (G3, G4 and G5) were examined for their ability to influence the activity of human erythrocyte plasma membrane adenosinetriphosphatases (ATPases). Plasma membrane ATPases are a group of enzymes related, among others, to the maintenance of ionic balance inside the cell. An inhibition of their activity may result in a disturbance of cell functioning. Two of examined dendrimers (G4 and G5) were found to inhibit the activity of Na(+)/K(+) ATPase and Ca(2+) ATPase by 20-30%. The observed effect was diminished when higher concentrations of dendrimers were used. The experiment with the use of pyrene as fluorescent probe sensitive to the changes in microenvironments polarity revealed that it was an effect of dendrimers self-aggregation. Additional studies showed that PAMAM-OH dendrimers were able to decrease the fluidity of human erythrocytes plasma membrane. Obtained results suggest that change in plasma membrane fluidity was not caused by the dendrimer-lipid interaction, but dendrimer-protein interaction. Different pattern of influence of dendrimers on ATPases activity and erythrocyte membrane fluidity suggests that observed change in ATPases activity is not a result of dendrimer-lipid interaction, but may be related to direct interaction between dendrimers and ATPases.
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In vivo toxicity of poly(propyleneimine) dendrimers.
J Biomed Mater Res A
PUBLISHED: 01-20-2011
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Dendrimers are highly branched macromolecules with the potential to be used for biomedical applications. Several dendrimers are toxic owing to their positively charged surfaces. However, this toxicity can be reduced by coating these peripheral cationic groups with carbohydrate residues. In this study, the toxicity of three types of 4th generation poly (propyleneimine) dendrimers were investigated in vivo; uncoated (PPI-g4) dendrimers, and dendrimers in which 25% or 100% of surface amino groups were coated with maltotriose (PPI-g4-25%m or PPI-g4-100%m), were administered to Wistar rats. Body weight, food and water consumption, and urine excretion were monitored daily. Blood was collected to investigate biochemical and hematological parameters, and the general condition and behavior of the animals were analyzed. Unmodified PPI dendrimers caused changes in the behavior of rats, a decrease in food and water consumption, and lower body weight gain. In the case of PPI-g4 and PPI-g4-25%m dendrimers, disturbances in urine and hematological and biochemical profiles returned to normal during the recovery period. PPI-g4-100%m was harmless to rats. The PPI dendrimers demonstrated dose- and sugar-modification-degree dependent toxicity. A higher dose of uncoated PPI dendrimers caused toxicity, but surface modification almost completely abolished this toxic effect.
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Time Evolution of the Aggregation Process of Peptides Involved in Neurodegenerative Diseases and Preventing Aggregation Effect of Phosphorus Dendrimers Studied by EPR.
Biomacromolecules
PUBLISHED: 10-19-2010
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A key pathological event of prion and Alzheimer diseases is the formation of prion and amyloid plaques generated by peptide aggregation in the form of fibrils. Dendrimers have revealed their ability to prevent fibril formation and therefore cure neurodegenerative diseases. To provide information about the kinetics and the mechanism of peptide fibril formation and about the ability of the dendrimers to prevent peptide aggregation, we performed a computer-aided EPR analysis of the selected nitroxide spin probe 4-octyl-dimethylammonium,2,2,6,6-tetramethyl-piperidine-1-oxyl bromide (CAT8) in water solutions of the ?-amyloid peptide A? 1-28 and the prion peptide PrP 185-208, which contain the fibril nucleation sites, in the absence and in the presence of phosphorus dendrimers. After a careful selection of the experimental conditions that allow aggregation to occur and to be monitored by EPR analysis over time, it was found that the A? 1-28 fibrils formed in 220 min at 0.5 mM peptide, 0.05 mM CAT8, 0.04 mg/mL heparin, and pH = 5. As a consequence, the interacting sites available for cooperative interactions with CAT8 were engaged in the peptide-peptide interactions and a fraction of the probe was extracted in the fluid fibril/water interphase, while another fraction was trapped at the peptide/peptide interphase, showing a decrease in mobility. Conversely, in the presence of the dendrimer (at the selected, after several trials, peptide/dendrimer molar ratio = 50), due to dipole-dipole interactions with peptide monomers, the probe remained at the dendrimer/peptide interphase and the spectral parameters negligibly changed over time. A fraction of probes inserted in PrP 185-208 low-packed aggregates and monitored their fast formation after 90 min. However, the binding organization of the prion peptide negligibly changed upon aggregation in comparison to A? 1-28. It is proposed that dendrimers mainly interfere in the lag (nucleation) phase of the prion peptide.
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Characterization of complexes formed by polypropylene imine dendrimers and anti-HIV oligonucleotides.
Colloids Surf B Biointerfaces
PUBLISHED: 09-24-2010
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Current anti-HIV therapies are capable of controlling viral infection but do not represent a definitive cure. They rely on the administration of antiretroviral nucleoside analogues, either alone or in combination with vectors. Dendrimers are branched, synthetic polymers with layered architectures, promising non-viral vectors in gene therapy. The aim of the paper was to study the interactions between three anti-HIV antisense oligonucleotides (ODNs): SREV, ANTI TAR, GEM91 and different generation polypropylene imine dendrimers (PPI) by monitoring changes in the fluorescence polarization of fluorescein attached to the ends of the ODNs when increasing concentrations of dendrimers were added. Laser Doppler electrophoresis, dynamic light scattering (DLS) and transmission electron microscopy (TEM) were used to characterize, respectively, zeta potential, particle size and morphology of dendriplexes formed in different molar ratios. Antisense oligonucleotides interacted with polypropylene imine dendrimers in different molar ratios depending on generation. Zeta potential of dendriplexes varied from (-25 to -21) mV to -5 mV (for PPIG3 and PPIG4 complexes) and to zero (for PPIG2 complexes). The structures presented a polydisperse size from about 50 nm to even 700-800 nm by TEM and about 250 nm by DLS. It means that besides single dendriplexes, aggregates were also present.
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Interactions of phosphorus-containing dendrimers with liposomes.
Biochim. Biophys. Acta
PUBLISHED: 07-22-2010
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The influence of cationic phosphorus-containing dendrimers generation 3 and 4 on model DMPC or DPPC lipid membranes was studied. Measurements of fluorescence anisotropy and differential scanning calorimetry (DSC) were applied to assess changes in lipid bilayer parameters, including fluidity, anisotropy, and phase-transition temperature. Interaction with both hydrophobic and hydrophilic regions of the bilayer was followed by these methods. Dendrimers of both generations influence lipid bilayers by decreasing membrane fluidity. The results suggest that dendrimers can interact both with the hydrophobic part and the polar head-group region of the phospholipid bilayer. Higher generation dendrimers interact more strongly with model membranes, and the concentration, as well as the generation, is of similar importance.
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Carbosilane dendrimers NN8 and NN16 form a stable complex with siGAG1.
Colloids Surf B Biointerfaces
PUBLISHED: 07-16-2010
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A new mechanism of gene expression inhibition has been discovered as RNA interference, in which the ability of double-stranded RNA to stimulate specific degradation of an mRNA target with a complementary sequence to one of the double-stranded RNA strands. Water-soluble carbosilane dendrimers containing ammonium or amine groups at their periphery are biocompatible molecules that may be good candidates as non-viral carriers of small interfering RNA. In studying the formation of complex between anti-HIV siRNA siGAG1 and carbosilane dendrimers NN8 and NN16 by circular dichroism, fluorescence, and zeta-potential, the size of nanoparticles formed has been estimated by dynamic light scattering. At a charge ratio of 1:3-4 (siGAG1:dendrimer), the dendriplexes formed were in the size range of 250-350 nm.
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New drug delivery nanosystem combining liposomal and dendrimeric technology (liposomal locked-in dendrimers) for cancer therapy.
J Pharm Sci
PUBLISHED: 06-22-2010
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Liposomal locked-in dendrimers (LLDs), the combination of liposomes and dendrimers in one formulation, represents a relatively new term in the drug carrier technology. LLDs undergone appropriate physicochemical investigation can merge the benefits of liposomal and dendrimeric nanocarriers. In this study generation 1 and 2 hydroxy-terminated dendrimers were synthesized and were then "locked" in liposomes consisting of DOPC/DPPG. The anticancer drug doxorubicin (Dox) was loaded into pure liposomes or LLDs and the final products were subjected to lyophilization. The loading of Dox as well as its in vitro release rate from all systems was determined and the interaction of liposomes with dendrimers was assessed by thermal analysis and fluorescence spectroscopy. The results were very promising in terms of drug encapsulation and release rate, factors that can alter the therapeutic profile of a drug with low therapeutic index such as Dox. Physicochemical methods revealed a strong, generation dependent, interaction between liposomes and dendrimers that probably is the basis for the higher loading and slower drug release from the LLDs comparing to pure liposomes.
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Interaction of the prion protein fragment PrP 185-206 with biological membranes: effect on membrane permeability.
J. Pept. Sci.
PUBLISHED: 06-17-2010
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Amyloids are proteinaceous aggregates related to the so-called conformational diseases, such as Alzheimers and prion diseases. The cytotoxicity of amyloids may be related to the interaction of the amiloidogenic peptides or proteins with the cell membrane. In order to gain information on the physico-chemical effects of amyloids on membranes, we have studied the interaction of the human prion amyloidogenic fragment PrP 185-206 with negatively charged model membranes. The results show that the peptide causes the destabilization of the membrane, making it permeable to potassium ions and to charged organic compounds. This effect correlates with the interaction of the peptide with the membrane, causing a variation in the magnitude of the electrostatic surface and dipole membrane potentials. This effect on the electrostatic properties of the membranes may help explaining the observed permeability: a neutralization of the surface negative charge and a decrease of the inside-positive dipole potential would facilitate the translocation of positive ions. The structural analysis of the peptide in the presence of model membranes reveals that it adopts a predominantly unordered structure without any signs of amyloid formation. The results may be relevant in relation to the recently described cell toxic capacity of the peptide.
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Interaction of cationic phosphorus dendrimers (CPD) with charged and neutral lipid membranes.
Colloids Surf B Biointerfaces
PUBLISHED: 05-21-2010
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Despite the rapid development of modern pharmaceutics, delivery of drugs to sites of action is not always effective. The research on new targeting delivery systems of pharmacologically active molecules is of great importance. Surface properties such as surface charge of drug delivery particles frequently define their pharmacokinetic profile; hence the efficiency of drugs can be increased by application of nanoparticles having appropriate surface properties. The aim of the present work was to study the interactions of cationic phosphorus-containing dendrimers (CPD) with model lipid membranes with no charge or bearing surface charge. The interactions of two generations of phosphorus dendrimers on the thermotropic behavior of model lipid membranes composed of DMPC (uncharged) or DMPC/DPPG (negatively charged) were studied using differential scanning calorimetry (DSC). The results of this study showed that CPDs can alter the thermotropic behaviour of the bilayer by reducing the cooperativity of phospholipids and this effect strongly depends on membrane surface charge. The information resulting from this study may be applied to the rational design of new drug carriers combining liposomal and dendrimeric technology.
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Influence of surface functionality of poly(propylene imine) dendrimers on protease resistance and propagation of the scrapie prion protein.
Biomacromolecules
PUBLISHED: 04-22-2010
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Accumulation of PrP(Sc), an insoluble and protease-resistant pathogenic isoform of the cellular prion protein (PrP(C)), is a hallmark in prion diseases. Branched polyamines, including PPI (poly(propylene imine)) dendrimers, are able to remove protease resistant PrP(Sc) and abolish infectivity, offering possible applications for therapy. These dendrimer types are thought to act through their positively charged amino surface groups. In the present study, the molecular basis of the antiprion activity of dendrimers was further investigated, employing modified PPI dendrimers in which the positively charged amino surface groups were substituted with neutral carbohydrate units of maltose (mPPI) or maltotriose (m3PPI). Modification of surface groups greatly reduced the toxicity associated with unmodified PPI but did not abolish its antiprion activity, suggesting that the presence of cationic surface groups is not essential for dendrimer action. PPI and mPPI dendrimers of generation 5 were equally effective in reducing levels of protease-resistant PrP(Sc) (PrP(res)) in a dose- and time-dependent manner in ScN2a cells and in pre-existing aggregates in homogenates from infected brain. Solubility assays revealed that total levels of PrP(Sc) in scrapie-infected mouse neuroblastoma (ScN2a) cells were reduced by mPPI. Coupled with the known ability of polyamino dendrimers to render protease-resistant PrP(Sc) in pre-existing aggregates of PrP(Sc) susceptible to proteolysis, these findings strongly suggest that within infected cells dendrimers reduce total amounts of PrP(Sc) by mediating its denaturation and subsequent elimination.
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Phenotype and functional analysis of human monocytes-derived dendritic cells loaded with a carbosilane dendrimer.
Biomaterials
PUBLISHED: 03-26-2010
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Dendritic cells (DCs) play a major role in development of cell-mediated immunotherapy due to their unique role in linking innate and adaptive immunities. In spite of improvement in this area, strategies employing ex vivo generated DCs have shown limited efficacy in clinical trials. Dendrimers have been proposed as new carriers for drug delivery in aim to ameliorate DCs antigen loading that is a pivotal point in DCs approaches. In this study, we have investigated the phenotypic and functional characteristics of human monocytes-derived dendritic cells after HIV-derived peptides uptake in vitro. We have found that iDCs and mDCs were able to capture efficiently water soluble carbosilane (CBS) dendrimer 2 G-NN16 and did not induce changes in maturation markers levels at the DCs surface. Therefore, CBS 2 G-NN16-loaded mDCs migrated as efficiently as unloaded DCs towards CCL19 or CCL21. Furthermore, DCs viability, activation of allogenic naïve CD4 + T cells by mDCs and secretion of cytokines were not significantly changed by 2 G-NN16 loading. Summing up, our data indicate that CBS 2 G-NN16 has no negative effects on the pivotal properties of DCs in vitro. It should therefore be feasible to further develop this antigen loading strategy for clinical use in immunotherapy against viral infections.
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How to study dendriplexes II: Transfection and cytotoxicity.
J Control Release
PUBLISHED: 07-28-2009
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This paper reviews different techniques for analyzing the transfection efficiencies and cytotoxicities of dendriplexes-complexes of nucleic acids with dendrimers. Analysis shows that three plasmids are mainly used in transfection experiments: plasmid DNA encoding luciferase from the firefly Photinus pyralis, beta-galactosidase, or green fluorescent protein. The effective charge ratio of transfection does not directly correlate with the charge ratio obtained from gel electrophoresis, zeta-potential or ethidium bromide intercalation data. The most popular cells for transfection studies are human embryonic kidney cells (HEK293), mouse embryonic cells (NIH/3T3), SV40 transformed monkey kidney fibroblasts (COS-7) and human epithelioid cervical carcinoma cells (HeLa). Cellular uptake is estimated using fluorescently-labeled dendrimers or nucleic acids. Transfection efficiency is measured by the luciferase reporter assay for luciferase, X-Gal staining or beta-galactosidase assay for beta-galactosidase, and confocal microscopy for green fluorescent protein. Cytotoxicity is determined by the MTT test and lactate dehydrogenase assays. On the basis of the papers reviewed, a standard essential set of techniques for characterizing dendriplexes was constructed: (1) analysis of size and shape of dendriplexes in dried/frozen state by electron or atomic force microscopy; (2) analysis of charge/molar ratio of complexes by gel electrophoresis or ethidium bromide intercalation assay or zeta-potential measurement; (3) analysis of hydrodynamic diameter of dendriplexes in solution by dynamic light scattering. For the evaluation of transfection efficiency the essential techniques are (4) luciferase reporter assay, beta-galactosidase assay or green fluorescent protein microscopy, and (5) cytotoxicity by the MTT test. All these tests allow the transfection efficiencies and cytotoxicities of different kinds of dendrimers to be compared.
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The immobilization of gossypol derivative on N-polyvinylpyrrolidone increases its water solubility and modifies membrane-active properties.
J. Med. Chem.
PUBLISHED: 07-17-2009
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The conjugate of the gossypol derivative megosin (1) with N-polyvinylpyrrolidone named rometin (2) was synthesized. The effects of 1 and 2 on the structure and permeability of human erythrocytes and rat liver mitochondria were compared. Compound 1 induced dose-dependent erythrocyte hemolysis and increased mitochondrial permeability, with concomitant changes in membrane structure as determined by ESR and fluorescence anisotropy methods. Immobilization of 1 on N-polyvinylpyrrolidone (compound 2) increased its water solubility and reduced the intensity of its effects on erythrocyte membrane integrity and mitochondrial permeability, which correlated with a decrease in the membranes structural changes induced by the compound. Although the same concentrations of free and N-polyvinylpyrrolidone bound 1 were used, far less (14)C-labeled 1 was incorporated into the membranes from complex than free 1. The increase in water solubility and the reduction of membrane-active properties of 1 after immobilization on N-polyvinylpyrrolidone could explain our previous observation of the decreased toxicity of 1.
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Use of polyamidoamine dendrimers to engineer BDNF-producing human mesenchymal stem cells.
Mol. Biol. Rep.
PUBLISHED: 06-23-2009
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We report the use of polyamidoamine (PAMAM-NH(2)) dendrimers along with other non-viral vehicles for the in vitro transfection of human bone marrow mesenchymal stem cells (hMSCs) and for engineering MSCs to secrete brain-derived neurotrophic factor (BDNF). Different generations of cationic polyamidoamine dendrimers (generations 3-6) were tested on HEK 293T cells. hMSCs were then transfected with PAMAM-NH(2) G4 dendrimers and Lipofectamine 2000, which elicited the expression of GFP reporter in around 6 and 20% of the cells, respectively. Both vehicles were then shown to elicit the expression of BDNF in MSCs from a bicistronic cassette. Non-virally induced neurotrophin expression may be a safe and easy method for adapting autologous stem cells for therapeutic treatment of diseases and neural system injuries.
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Transfection efficiencies of PAMAM dendrimers correlate inversely with their hydrophobicity.
Int J Pharm
PUBLISHED: 06-18-2009
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Dendriplexes were characterized by ethidium bromide intercalation assay and their transfection efficiency was studied using HEK 293 cells and human mesenchymal stem cells. PAMAM G4 showed a higher transfection efficiency than PAMAM G3-G6, G4-OH, G4-25% or G4-50% dendrimers. Substitution of OH groups for the NH(2) surface groups rendered the dendrimer unable to form dendriplexes and to transfect cells. Partial (25%) substitution of CH(3) groups for the NH(2) groups markedly impaired transfection; 50% substitution decreased the ability of PAMAM G4 to transfect threefold. It was concluded that increased hydrophobicity decreased the ability of dendrimers to transfect. PAMAM G4-50% is highly hydrophobic and forms micelles in solution, which can transfect pGFP. The results of ethidium bromide intercalation assays, ANS fluorescence studies and transfection efficiencies of PAMAM dendrimers were correlated. Subsequently, we constructed a neurotrophin-encoding plasmid and studied its delivery to mesenchymal stem cells using PAMAM G4 dendrimer and Lipofectamine 2000. Lipofectamine 2000 was a more effective carrier (18.5%) than PAMAM G4 dendrimer (1.2%).
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Binding properties of water-soluble carbosilane dendrimers.
J Fluoresc
PUBLISHED: 05-19-2009
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Dendrimers have been proposed as new carriers for drug delivery. They have distinctive characteristics, such as uniform and controlled size, monodispersity and modifiable surface group functionality, which make them extremely useful for biomedical applications. In this study, the binding capacity of water-soluble carbosilane dendrimers was examined. A double fluorimetric titration method with 1-anilinonaphthalene-8-sulphonic acid (ANS) was used to estimate the binding constant and the number of binding centers per dendrimer molecule. The data obtained suggest that ANS interacts non-covalently with the dendrimers. Second generation dendrimers have an open, asymmetric structure that allows them to encapsulate ANS. The ability of the polymers to interact with DNA was assessed by an ethidium bromide (EB) displacement assay. All the dendrimers studied bound to DNA in competition with EB, though the strength of binding varied. Dendrimer interactions with a protein (BSA) were tested using fluorescence quenchers. The dendrimers caused no conformation change in the protein, indicating that interactions between carbosilane dendrimers and BSA are weak and occur preferentially at the protein surface.
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The interaction of PVP complexes of gossypol and its derivatives with an artificial membrane lipid matrix.
Cell. Mol. Biol. Lett.
PUBLISHED: 03-20-2009
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In this paper, we present the results of a study on the membrane-active properties of gossypol, its derivatives and their polyvinylpyrrolidone complexes as assessed by differential scanning calorimetry and by the fluorescent probe method. The latter revealed the change in polarization of the incident radiation caused by the action of the polyphenol on the artificial membrane lipid matrix.
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How to study dendriplexes I: Characterization.
J Control Release
PUBLISHED: 01-23-2009
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This paper reviews the different techniques for analyzing the formation, physical-chemical characterization and stability of dendriplexes-complexes of nucleic acids with dendrimers. It does not touch on the questions of transfection efficiency or the cytotoxicity of dendriplexes. On the basis of the papers reviewed, a standard essential set of techniques for characterizing dendriplexes was constructed: (1) analysis of size and shape of dendriplexes in dried/frozen state by electron or atomic force microscopy; (2) analysis of charge/molar ratio of complexes by gel electrophoresis or ethidium bromide intercalation assay or zeta potential; (3) analysis of hydrodynamic diameter of dendriplexes in solution by dynamic light scattering; and analysis of (4) transfection efficiency and (5) cytotoxicity.
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Acidosis, magnesium and acetylsalicylic acid: effects on thrombin.
Spectrochim Acta A Mol Biomol Spectrosc
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Thrombin, an enzyme from the hydrolase family, is the main component of the blood coagulation system. In ischemic stroke it acts as a serine protease that converts soluble fibrinogen into insoluble strands of fibrin forming blood clots in the brain. It has been found to phosphoresce at room temperature in the millisecond and microsecond ranges. The phosphorescence of thrombin was studied under physiological conditions, in acidosis (decrease of pH from 8.0 to 5.0) and on the addition of salts (magnesium sulfate and sodium chloride) and of acetylsalicylic acid, and its connection with thrombin function is discussed. Acidosis significantly increased the internal dynamics of thrombin. We propose that lactate-acidosis plays a protective role in stroke, preventing the formation of clots. The addition of NaCl and MgSO(4) in different concentrations increased the internal dynamics of thrombin. Also, the addition of MgSO(4) decreased thrombin-induced platelet aggregation. However, magnesium sulfate and acetylsalicylic acid in the therapeutic concentrations used for treatment of ischemic stroke had no effect on thrombin internal dynamics. The data obtained will help to elucidate the conformational stability of thrombin under conditions modulating lactate-acidosis and in the presence of magnesium sulfate.
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Effect of viologen-phosphorus dendrimers on acetylcholinesterase and butyrylcholinesterase activities.
Int. J. Biol. Macromol.
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The inhibition of acetylcholinesterase (AChE) and butyrylcholinesterase (BChE) is the first step in checking whether new compounds can be considered as drugs for treating neurodegenerative diseases. The effect of viologen-phosphorus dendrimers on AChE and BChE activities was studied. The results show that the effects on the cholinesterase activities depend on dendrimer type and size. Viologen dendrimers can interact with the enzymes in two ways: they can bind either to a peripheral site of the enzyme or to amino acids located near the active site, inhibiting catalysis by both cholinesterases. All tested non-toxic viologen-phosphorus dendrimers inhibited the activities of both cholinesterases, showing their potential as new drugs for treating neurodegenerative diseases.
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Stability of dendriplexes formed by anti-HIV genetic material and poly(propylene imine) dendrimers in the presence of glucosaminoglycans.
J Phys Chem B
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There are several barriers to the application of dendriplexes formed by poly(propylene imine) dendrimers and genetic material for gene therapy. One limitation is their interaction with extracellular matrix components such as glucosaminoglycans. These can displace the genetic material from the dendriplexes, affecting their transfection activity. In this study, we analyzed the interaction between dendriplexes and the four main glucosaminoglycans (heparin, heparan sulfate, chondroitin sulfate, and hyaluronic acid) by fluorescence polarization and gel electrophoresis. Dendriplexes were formed by combining three anti-HIV antisense oligodeoxynucleotides with three poly(propylene imine) dendrimers of the fourth generation: unmodified and partially modified with maltose and maltotriose (open shell glycodendrimers). The data showed that the effect of glucosaminoglycans on dendriplexes depends on the glucosaminoglycan type and the oligosaccharide serving as the surface group of the dendrimer. Heparin at physiological concentrations destroys dendriplexes formed by open shell glycodendrimers, but dendriplexes based on unmodified poly(propylene imine) dendrimers are stable in its presence. The other glucosaminoglycans at physiological concentrations cannot destroy dendriplexes formed by any of the dendrimers studied.
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Complexation of HIV derived peptides with carbosilane dendrimers.
Colloids Surf B Biointerfaces
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Dendrimers have been proposed as new carriers for selected HIV-1 peptides. This paper reports on the complexation behaviour of the three HIV-derived-peptides: Gp160, NH-EIDNYTNTIYTLLEE-COOH; P24, NH-DTINEEAAEW-COOH and Nef, NHGMDDPEREVLEWRFDSRLAF-COOH with second generation cationic carbosilane dendrimers (CBD) branched with carbonsilicon bonds (CBD-CS) or oxygensilicon bonds (CBD-OS). Studies on the formation of complexes between HIV peptides and CBDs by fluorescence polarization, zeta-potential, electrophoresis and transmission electron microscopy have shown that both studied dendrimers form complexes with HIV peptides. At a molar ratio of (2.5-3):1 (dendrimer:peptide), the complexes formed were in the size range of 180-275 nm and with significant positive surface charge. The results suggest that interactions between dendrimers and HIV peptides have electrostatic nature due to the negative charge of peptides backbone and positive charge of dendrimer functional groups. Dendriplex stability depended on the type of studied dendrimers. Time of peptides release from the complexes ranged from 1 (CBD-OS) to ~36 (CBD-CS)h. Basing on the obtained results, we propose that the water-soluble cationic carbosilane dendrimers can be considered for delivery of HIV peptides to dendritic cells.
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Poly(propylene imine) dendrimers modified with maltose or maltotriose protect phosphorothioate oligodeoxynucleotides against nuclease activity.
Biochem. Biophys. Res. Commun.
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The antisense oligonucleotides are promising agents for application in anti-HIV therapies. The antiretroviral nucleoside analogues administrated into circulatory system are vulnerable to nuclease degradation and require a vehicle which would not only facilitate therapeutic nucleotides into host cells, but would also provide protection against enzymatic degradation. Such potential is exhibited by poly(propylene imine) dendrimers - the branched cationic polymers easily interacting with oligonucleotides to form complexes called "dendriplexes". The aim of the present study was to evaluate the abilities of the fourth generation poly(propylene imine) dendrimers partially modified with maltose (PPI-Mal G4) or maltotriose (PPI-Mal-III G4) to protect anti-HIV antisense oligonucleotides (ODNs) from nucleolytic degradation. The ODNs (AT, GEM91, SREV) were complexed with dendrimers and subjected to cleavage by serum nucleases or endonuclease S1. The results showed that all examined dendrimers protected ODNs against nucleases contained in FBS. Both PPI-Mal G4 and PPI-Mal-III G4 dendrimers completely prevented ODNs digestion by nuclease S1 at neutral pH. The protective capabilities of investigated dendrimers were significantly weaker in acidic environment. The time stability assay showed that the dendriplexes formed by AT, GEM91, SREV and carbohydrate-modified PPI G4 dendrimers still existed after 12h incubation both in low and at neutral pH buffers. The conformational change of dendriplexes in acidic environment was proposed as possible phenomenon leading to exposition of ODNs to nuclease attack and significantly diminishing dendriplexes resistance to nucleolitic digestion.
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Influence of fourth generation poly(propyleneimine) dendrimers on blood cells.
J Biomed Mater Res A
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Dendrimers provide many exciting opportunities for potential biomedical applications. However, owing to their positively charged surfaces, poly(propyleneimine) (PPI) dendrimers show toxic and haemolytic activities. One of the methods for masking the peripheral cationic groups is to modify them using carbohydrate residues. In this study, three types of the fourth generation PPI dendrimers-uncoated (PPI-g4), approximately 35% maltotriose (Mal-III)-coated (PPI-g4-OS), and approximately 90% Mal-III-coated (PPI-g4-DS) were investigated by assessing their effects on red blood cell (RBC) haemolysis in samples of pure RBCs, RBCs in the presence of human serum albumin (HSA) or human plasma, and RBCs in whole blood. Lymphocyte proliferation and platelet (PLT) aggregation were also studied in the presence of various concentrations of dendrimers. Although all dendrimers examined affected all the blood cells studied, the unmodified PPI-g4 had the most damaging effect. It caused high RBC haemolysis rates and PLT aggregation and greatly inhibited lymphocyte proliferation. These effects were caused by the cationic surface of this polymer. The modification of PPI-g4 with Mal-III reduced the effect of the dendrimer on all blood cells. The presence of HSA or plasma in the buffer containing the RBCs or RBC in whole blood significantly decreased the extent of dendrimer-driven haemolysis.
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Genotoxicity of poly(propylene imine) dendrimers.
Biopolymers
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Dendrimers are highly branched macromolecules with the potential in biomedical applications. Due to positively charged surfaces, several dendrimers reveal toxicity. Coating peripheral cationic groups with carbohydrate residues can reduce it. In this study, the cytotoxicity and genotoxicity of three types of 4th generation poly(propylene imine) dendrimers were investigated. Peripheral blood mononuclear cells (PBMCs) were treated with uncoated (PPI-g4) dendrimers, and dendrimers in which approximately 40% or 90% of peripheral amino groups were coated with maltotriose (PPI-g4-OS or PPI-g4-DS) at concentration of 0.05, 0.5, 5 mg/ml. Abbreviations OS and DS stand for open shell and dense shell respectively, that describes the structure of carbohydrate modified dendrimers. After 1 h of cell incubation at 37°C, the MTT and comet assays were performed. PPI dendrimers demonstrated surface-modification-degree dependent toxicity, although genotoxicity of PPI-g4 and PPI-g4-OS measured by the comet assay was concentration dependent up to 0.5 mg/ml and at 5 mg/ml the amount of DNA that left comets head decreased. Results may suggest a strong interaction between dendrimers and DNA, and furthermore, that coating PPI dendrimers by maltoriose is an efficient method to reduce their genotoxicity what opens the possibilities to use them as therapeutic agents or drug carriers.
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siRNA carriers based on carbosilane dendrimers affect zeta potential and size of phospholipid vesicles.
Biochim. Biophys. Acta
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One of the major limitations in gene therapy is an inability of naked siRNA to passively diffuse through negatively charged cell membranes. Therefore, the siRNA transport into a cell requires efficient carriers. In this work we analyzed the charge-dependent interaction of the complexes of cationic carbosilane dendrimers (CBD) and anti-HIV siRNA (dendriplexes) with the model membranes - large unilamellar vesicles (LUV). We used the second generation of branched with CBD carbon-silicon bonds (CBD-CS) which are water-stable and that of oxygen-silicon bonds (CBD-OS) which are slowly hydrolyzed in aqueous solutions. The LUVs were composed of zwitterionic dimyristoylphosphatidylcholine (DMPC), negatively charged dipalmitoylphosphatidylglycerol (DPPG) and their mixture (DMPC/DPPG, molar ratio 7:3). The interaction of dendriplexes with LUVs affected both zeta potential and size of the vesicles. The changes of these values were larger for the negatively charged LUV. CBD-CS resulted in the decrease of zeta potential values to more negative ones, whereas an opposite effect took place for CBD-OS suggesting a different kind of interaction between LUVs and the dendriplexes. The results indicate that both CBD-CS and CBD-OS can be used for transport of siRNA into the cells. However, CBD-CS are preferred due to a better stability in water and improved bioavailability of siRNA on their surface.
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Surface modification of PAMAM dendrimer improves its biocompatibility.
Nanomedicine
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Modification of dendrimer surface groups is one of the methods available to obtain compounds characterized by reduced toxicity. This article reports results of preliminary biocompatibility studies of a modified polyamidoamine dendrimer of the fourth generation. Reaction with dimethyl itaconate resulted in transformation of surface amine groups into pyrrolidone derivatives. Interaction of the modified dendrimer with human serum albumin (HSA) was analyzed. The influence of the dendrimer on mouse neuroblastoma cell line viability and its hemolytic properties were also investigated. The binding constant between analyzed dendrimer and HSA was found to be equal to 1.2 × 10(5) ± 0.2 × 10(5) M(-1). Small changes in HSA secondary structure were observed. The analyzed dendrimer revealed minor toxic activity, as diminishment in cell viability was observed only for dendrimer concentrations higher than 2 mg/mL. Moreover, under the applied experimental conditions, no hemolytic activity was observed. Those observations point to the potential of the analyzed compound for further studies toward its applicability in nanomedicine.
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Carbosilane dendrimers are a non-viral delivery system for antisense oligonucleotides: characterization of dendriplexes.
J Biomed Nanotechnol
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The success of gene therapy depends on the development of suitable carriers, and because of their architecture dendrimers are promising tools for gene delivery. This research concerns the use of second generation carbosilane dendrimers as carriers for anti-HIV oligodeoxynucleotides (ODNs). The aim was to characterize complexes formed by positively charged dendrimers and negatively charged oligonucleotides using a fluorescence method, laser Doppler electrophoresis, dynamic light scattering (DLS), atomic force microscopy (AFM), transmission electron microscopy (TEM) and molecular modeling. The zeta-potential of ODNs increased from -25 mV to positive values after the addition of dendrimers. DLS and TEM revealed that the diameters of dendriplexes ranged from 75 to 240 nm and from 50 to 260 nm, respectively, and this was dependent on the type of dendrimer and the molar ratios of the complexes formed; complexes were stable for between 100 and 300 minutes. AFM measurements and molecular modeling studies were carried out to determine the structure and size of dendriplexes. The physicochemical properties of the dendriplexes studied and data from previous research suggest that carbosilane dendrimers are good candidates for nucleic acid delivery.
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Stabilization of erythrocytes against oxidative and hypotonic stress by tannins isolated from sumac leaves (Rhus typhina L.) and grape seeds (Vitis vinifera L.).
Cell. Mol. Biol. Lett.
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Erythrocytes are constantly exposed to ROS due to their function in the organism. High tension of oxygen, presence of hemoglobin iron and high concentration of polyunsaturated fatty acids in membrane make erythrocytes especially susceptible to oxidative stress. A comparison of the antioxidant activities of polyphenol-rich plant extracts containing hydrolysable tannins from sumac leaves (Rhus typhina L.) and condensed tannins from grape seeds (Vitis vinifera L.) showed that at the 5-50 ?g/ml concentration range they reduced to the same extent hemolysis and glutathione, lipid and hemoglobin oxidation induced by erythrocyte treatment with 400 ?M ONOO(-) or 1 mM HClO. However, extract (condensed tannins) from grape seeds in comparison with extract (hydrolysable tannins) from sumac leaves stabilized erythrocytes in hypotonic NaCl solutions weakly. Our data indicate that both hydrolysable and condensed tannins significantly decrease the fluidity of the surface of erythrocyte membranes but the effect of hydrolysable ones was more profound. In conclusion, our results indicate that extracts from sumac leaves (hydrolysable tannins) and grape seeds (condensed tannins) are very effective protectors against oxidative damage in erythrocytes.
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Dendrimer-driven neurotrophin expression differs in temporal patterns between rodent and human stem cells.
Mol. Pharm.
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This study reports the use of a nonviral expression system based on polyamidoamine dendrimers for time-restricted neurotrophin overproduction in mesenchymal stem cells and skin precursor-derived Schwann cells. The dendrimers were used to deliver plasmids for brain-derived neurotrophic factor (BDNF) or neurotrophin-3 (NT-3) expression in both rodent and human stem cells, and the timelines of expression were studied. We have found that, despite the fact that transfection efficiencies and protein expression levels were comparable, dendrimer-driven expression in human mesenchymal stem cells was characterized by a more rapid decline compared to rodent cells. Transient expression systems can be beneficial for some neurotrophins, which were earlier reported to cause unwanted side effects in virus-based long-term expression models. Nonviral neurotrophin expression is a biologically safe and accessible alternative to increase the therapeutic potential of autologous adult stem cells and stem cell-derived functional differentiated cells.
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The influence of maltose modified poly(propylene imine) dendrimers on hen egg white lysozyme structure and thermal stability.
Colloids Surf B Biointerfaces
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In this study the influence of dendrimers surface modification upon the strength of interaction with proteins was examined. Unmodified, cationic poly(propylene imine) dendrimer of the fourth generation (PPI G4), two PPI G4 dendrimers, partially and fully coated with maltose residues, and anionic polyamidoamine dendrimer of the third and a half generation (PAMAM G3.5 dendrimer), were used in the study. Hen egg white lysozyme, which possesses a cationic net charge under physiological conditions, was chosen as a model protein. The influence of dendrimers on the thermal stability of lysozyme was studied using differential scanning calorimetry (DSC) and circular dichroism (CD) methods. Additionally, the effect of dendrimers on the availability of lysozyme tryptophan residues to fluorescence quenchers was examined. It was shown that modification of dendrimer surface with maltose reduced its influence on lysozyme properties. However, even full surface modification, resulting in a neutral surface charge, did not deprive dendrimer of the ability to interact with the protein. It was probably caused by the introduction of a large number of hydroxyl groups from maltose residues on the surface of the dendrimer. In the study a comparable strength of influence exerted on lysozyme by cationic PPI dendrimer and anionic PAMAM G3.5 dendrimer was observed. The possible explanation of this fact is the presence of both positively and negatively charged areas on the surface of lysozyme. Such areas allow dendrimers possessing opposite surface charges to interact with lysozyme.
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Modulation of biogenic amines content by poly(propylene imine) dendrimers in rats.
J. Physiol. Biochem.
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Biogenic amines and polyamines participate in all vital organism functions, their levels being important function determinants. Studies were performed to check whether repeated administration of poly(propylene imine) (PPI) dendrimers, synthetic macromolecules with diaminobutane core, and peripheral primary amine groups, may influence the endogenous level of amines, as represented by the two of them: spermidine, a natural derivative of diaminobutane, and histamine. The experiment was carried out on Wistar rats. Fourth generation PPI dendrimer, as well as maltotriose-modified fourth generation PPI dendrimers with (a) cationic open sugar shell and (b) neutral dense sugar shell that possess a higher biocompatibility, was used. Applying the combination of column chromatography on Cellex P and spectrofluorimetric assays of o-phthaldialdehyde, the final amine condensation products were employed to analyze tissue spermidine and histamine outside the central nervous system. Furthermore, radioenzymatic assay was used to measure histamine levels in the brain. The obtained results indicate that in some tissues, the endogenous concentrations of histamine and spermidine may be affected by dendrimers depending on their dose and type of dendrimers.
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Phosphorus-containing dendrimers against ?-synuclein fibril formation.
Int. J. Biol. Macromol.
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The aim of this work was to study the effect of phosphorus-containing dendrimers (generations G3 and G4) on the fibrillation of ?-synuclein (ASN). The inhibition of fibril formation (filamentous and aggregates) is a potential therapeutic strategy for neurodegenerative disorders such as Parkinsons and other motor disorder neurodegenerative diseases. The interaction between phosphorus-containing dendrimers and ASN was studied by fluorescence spectroscopy. The decrease in the fluorescence intensity of intrisinic tyrosine was the most marked change in the fluorescence intensity observed upon addition of dendrimers. Furthermore, the effect of dendrimers on ASN fibril formation was studied using circular dichroism (CD) spectroscopy and CD studies were complemented by fluorescence assays using the dye thioflavin T (ThT). The results showed that phosphorus-containing dendrimers G3 and G4 inhibited fibril formation, when they were used in the ASN/dendrimer ratios 1:0.1 and 1:0.5. However, the higher concentrations of dendrimers did not show this effect.
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Cationic carbosilane dendrimers-lipid membrane interactions.
Chem. Phys. Lipids
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The aim of this work was to study interactions between cationic carbosilane dendrimers (CBS) and lipid bilayers or monolayers. Two kinds of second generation carbosilane dendrimers were used: NN16 with Si-O bonds and BDBR0011 with Si-C bonds. The results show that cationic carbosilane dendrimers interact both with liposomes and lipid monolayers. Interactions were stronger for negatively charged membranes and high concentration of dendrimers. In liposomes interactions were studied by measuring fluorescence anisotropy changes of fluorescent labels incorporated into the bilayer. An increase in fluorescence anisotropy was observed for both fluorescent probes when dendrimers were added to lipids that means the decreased membrane fluidity. Both the hydrophobic and hydrophilic parts of liposome bilayers became more rigid. This may be due to dendrimers incorporation into liposome bilayer. For higher concentrations of both dendrimers precipitation occurred in negatively charged liposomes. NN16 dendrimer interacted stronger with hydrophilic part of bilayers whereas BDBR0011 greatly modified the hydrophobic area. Monolayers method brought similar results. Both dendrimers influenced lipid monolayers and changed surface pressure. For negatively charged lipids the monitored parameter changed stronger than for uncharged DMPC lipids. Moreover, NN16 dendrimer interacted stronger than the BDBR0011.
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