In JoVE (1)

Other Publications (14)

Articles by Rameshwar Patil in JoVE

Other articles by Rameshwar Patil on PubMed

Side-chain Modified Analogues of Histaprodifen: Asymmetric Synthesis and Histamine H1-receptor Activity

Bioorganic & Medicinal Chemistry Letters. Feb, 2006  |  Pubmed ID: 16266803

New analogues of histaprodifen with polar side chains have been stereoselectively synthesized and evaluated as histamine H(1)-receptor agonists. As a key transformation the asymmetric aminohydroxylation has been used, which was successfully realized for the first time on an imidazolyl derivative. While all chiral analogues proved to be weak H(1)-receptor antagonists, an achiral keto derivative of histaprodifen turned out to be the first 2-acylated histamine congener displaying partial H(1)-receptor agonism (relative potency 12%).

Brain Tumor Tandem Targeting Using a Combination of Monoclonal Antibodies Attached to Biopoly(beta-L-malic Acid)

Journal of Controlled Release : Official Journal of the Controlled Release Society. Oct, 2007  |  Pubmed ID: 17630012

Tumor-specific targeting using achievements of nanotechnology is a mainstay of increasing efficacy of anti-tumor drugs. To improve drug targeting we covalently conjugated for the first time two different monoclonal antibodies, an anti-mouse transferrin receptor antibody and a mouse autoimmune anti-nucleosome antibody 2C5, onto the drug delivery nanoplatform, poly(beta-L-malic acid). The active anti-tumor drug components attached to the same carrier molecule were antisense oligonucleotides to vascular protein laminin-8. The resulting drug, a new Polycefin variant, was administered intravenously into glioma-bearing xenogeneic animals. The drug delivery system was targeted across mouse endothelial system by the anti-mouse transferring receptor antibody and to the tumor cell surface by the anti-nucleosome antibody 2C5. The targeting efficacies of the Polycefin variants bearing either two antibodies or each single antibody were compared in vitro and in vivo. ELISA confirmed the co-existence of two antibodies on the same nanoplatform molecule and their functional activities. Fluorescence imaging analysis after 24 h of intravenous injection demonstrated significantly higher tumor accumulation of Polycefin variants with the tandem configuration of antibodies than with single antibodies. The results suggest improved efficacy for tandem configuration of antibodies than for single configurations carried by a drug delivery vehicle.

Temozolomide Delivery to Tumor Cells by a Multifunctional Nano Vehicle Based on Poly(β-L-malic Acid)

Pharmaceutical Research. Nov, 2010  |  Pubmed ID: 20387095

Temozolomide (TMZ) is a pro-drug releasing a DNA alkylating agent that is the most effective drug to treat glial tumors when combined with radiation. TMZ is toxic, and therapeutic dosages are limited by severe side effects. Targeted delivery is thus needed to improve efficiency and reduce non-tumor tissue toxicity.

Phosphodiesterase Type 5 Inhibitors Increase Herceptin Transport and Treatment Efficacy in Mouse Metastatic Brain Tumor Models

PloS One. 2010  |  Pubmed ID: 20419092

Chemotherapeutic drugs and newly developed therapeutic monoclonal antibodies are adequately delivered to most solid and systemic tumors. However, drug delivery into primary brain tumors and metastases is impeded by the blood-brain tumor barrier (BTB), significantly limiting drug use in brain cancer treatment.

Inhibition of Brain Tumor Growth by Intravenous Poly (β-L-malic Acid) Nanobioconjugate with PH-dependent Drug Release [corrected]

Proceedings of the National Academy of Sciences of the United States of America. Oct, 2010  |  Pubmed ID: 20921419

Effective treatment of brain neurological disorders such as Alzheimer's disease, multiple sclerosis, or tumors should be possible with drug delivery through blood-brain barrier (BBB) or blood-brain tumor barrier (BTB) and targeting specific types of brain cells with drug release into the cell cytoplasm. A polymeric nanobioconjugate drug based on biodegradable, nontoxic, and nonimmunogenic polymalic acid as a universal delivery nanoplatform was used for design and synthesis of nanomedicine drug for i.v. treatment of brain tumors. The polymeric drug passes through the BTB and tumor cell membrane using tandem monoclonal antibodies targeting the BTB and tumor cells. The next step for polymeric drug action was inhibition of tumor angiogenesis by specifically blocking the synthesis of a tumor neovascular trimer protein, laminin-411, by attached antisense oligonucleotides (AONs). The AONs were released into the target cell cytoplasm via pH-activated trileucine, an endosomal escape moiety. Drug delivery to the brain tumor and the release mechanism were both studied for this nanobiopolymer. Introduction of a trileucine endosome escape unit resulted in significantly increased AON delivery to tumor cells, inhibition of laminin-411 synthesis in vitro and in vivo, specific accumulation in brain tumors, and suppression of intracranial glioma growth compared with pH-independent leucine ester. The availability of a systemically active polymeric drug delivery system that passes through the BTB, targets tumor cells, and inhibits glioma growth gives hope for a successful strategy of glioma treatment. This delivery system with drug release into the brain-specific cell type could be useful for treatment of various brain pathologies.

Nanoconjugate Platforms Development Based in Poly(β,L-Malic Acid) Methyl Esters for Tumor Drug Delivery

Journal of Nanotechnology. 2010  |  Pubmed ID: 23024655

New copolyesters derived from poly(β,L-malic acid) have been designed to serve as nanoconjugate platforms in drug delivery. 25% and 50% methylated derivatives (coPMLA-Me(25)H(75) and coPMLA-Me(50)H(50)) with absolute molecular weights of 32 600 Da and 33 100 Da, hydrodynamic diameters of 3.0 nm and 5.2 nm and zeta potential of -15mV and -8.25mV, respectively, were found to destabilize membranes of liposomes at pH 5.0 and pH 7.5 at concentrations above 0.05mg/mL. The copolymers were soluble in PBS (half life of 40 hours) and in human plasma (half life of 15 hours) but they showed tendency to aggregate at high levels of methylation. Fluorescence-labeled copolymers were internalized into MDA-MB-231 breast cancer cells with increased efficiency for the higher methylated copolymer. Viability of cultured brain and breast cancer cell lines indicated moderate toxicity that increased with methylation. The conclusion of the present work is that partially methylated poly(β,L-malic acid) copolyesters are suitable as nanoconjugate platforms for drug delivery.

Nanoplatforms for Constructing New Approaches to Cancer Treatment, Imaging, and Drug Delivery: What Should Be the Policy?

NeuroImage. Jan, 2011  |  Pubmed ID: 20149882

Nanotechnology is the design and assembly of submicroscopic devices called nanoparticles, which are 1-100 nm in diameter. Nanomedicine is the application of nanotechnology for the diagnosis and treatment of human disease. Disease-specific receptors on the surface of cells provide useful targets for nanoparticles. Because nanoparticles can be engineered from components that (1) recognize disease at the cellular level, (2) are visible on imaging studies, and (3) deliver therapeutic compounds, nanotechnology is well suited for the diagnosis and treatment of a variety of diseases. Nanotechnology will enable earlier detection and treatment of diseases that are best treated in their initial stages, such as cancer. Advances in nanotechnology will also spur the discovery of new methods for delivery of therapeutic compounds, including genes and proteins, to diseased tissue. A myriad of nanostructured drugs with effective site-targeting can be developed by combining a diverse selection of targeting, diagnostic, and therapeutic components. Incorporating immune target specificity with nanostructures introduces a new type of treatment modality, nano-immunochemotherapy, for patients with cancer. In this review, we will discuss the development and potential applications of nanoscale platforms in medical diagnosis and treatment. To impact the care of patients with neurological diseases, advances in nanotechnology will require accelerated translation to the fields of brain mapping, CNS imaging, and nanoneurosurgery. Advances in nanoplatform, nano-imaging, and nano-drug delivery will drive the future development of nanomedicine, personalized medicine, and targeted therapy. We believe that the formation of a science, technology, medicine law-healthcare policy (STML) hub/center, which encourages collaboration among universities, medical centers, US government, industry, patient advocacy groups, charitable foundations, and philanthropists, could significantly facilitate such advancements and contribute to the translation of nanotechnology across medical disciplines.

Polymalic Acid-based Nanobiopolymer Provides Efficient Systemic Breast Cancer Treatment by Inhibiting Both HER2/neu Receptor Synthesis and Activity

Cancer Research. Feb, 2011  |  Pubmed ID: 21303974

Biodegradable nanopolymers are believed to offer great potential in cancer therapy. Here, we report the characterization of a novel, targeted, nanobiopolymeric conjugate based on biodegradable, nontoxic, and nonimmunogenic PMLA [poly(β-l-malic acid)]. The PMLA nanoplatform was synthesized for repetitive systemic treatments of HER2/neu-positive human breast tumors in a xenogeneic mouse model. Various moieties were covalently attached to PMLA, including a combination of morpholino antisense oligonucleotides (AON) directed against HER2/neu mRNA, to block new HER2/neu receptor synthesis; anti-HER2/neu antibody trastuzumab (Herceptin), to target breast cancer cells and inhibit receptor activity simultaneously; and transferrin receptor antibody, to target the tumor vasculature and mediate delivery of the nanobiopolymer through the host endothelial system. The results of the study showed that the lead drug tested significantly inhibited the growth of HER2/neu-positive breast cancer cells in vitro and in vivo by enhanced apoptosis and inhibition of HER2/neu receptor signaling with suppression of Akt phosphorylation. In vivo imaging analysis and confocal microscopy demonstrated selective accumulation of the nanodrug in tumor cells via an active delivery mechanism. Systemic treatment of human breast tumor-bearing nude mice resulted in more than 90% inhibition of tumor growth and tumor regression, as compared with partial (50%) tumor growth inhibition in mice treated with trastuzumab or AON, either free or attached to PMLA. Our findings offer a preclinical proof of concept for use of the PMLA nanoplatform for combination cancer therapy.

The Optimization of Polymalic Acid Peptide Copolymers for Endosomolytic Drug Delivery

Biomaterials. Aug, 2011  |  Pubmed ID: 21514661

Membranolytic macromolecules are promising vehicles for cytoplasmic drug delivery, but their efficiency and safety remains primary concerns. To address those concerns, membranolytic properties of various poly(β-L-malic acid) (PMLA) copolymers were extensively investigated as a function of concentration and pH. PMLA, a naturally occurring biodegradable polymer, acquires membranolytic activities after substitution of pendent carboxylates with hydrophobic amino acid derivatives. Ruled by hydrophobization and charge neutralization, membranolysis of PMLA copolymers increased as a function of polymer molecular weight and demonstrated a maximum with 50% substitution of carboxylates. Charge neutralization was achieved either conditionally by pH-dependent protonation or permanently by masking carboxylates. Membranolysis of PMLA copolymers containing tripeptides of leucine, tryptophan and phenylalanine were pH-dependent in contrast to pH-independent copolymers of Leucine ethyl ester and Leu-Leu-Leu-NH(2) with permanent charge neutralization. PMLA and tripeptides seemed a unique combination for pH-dependent membranolysis. In contrast to nontoxic pH-dependent PMLA copolymers, pH-independent copolymers were found toxic at high concentration, which is ascribed to their nonspecific disruption of plasma membrane at physiological pH. pH-Dependent copolymers were membranolytically active only at acidic pH typical of maturating endosomes, and are thus devoid of cytotoxicity. The PMLA tripeptide copolymers are useful for safe and efficient cytoplasmic delivery routed through endosome.

Poly(methyl Malate) Nanoparticles: Formation, Degradation, and Encapsulation of Anticancer Drugs

Macromolecular Bioscience. Oct, 2011  |  Pubmed ID: 21793213

PMLA nanoparticles with diameters of 150-250 nm are prepared, and their hydrolytic degradation is studied under physiological conditions. Degradation occurs by hydrolysis of the side chain methyl ester followed by cleavage of the main-chain ester group with methanol and L-malic acid as the final degradation products. No alteration of the cell viability is found after 1 h of incubation, but toxicity increases significantly after 3 d, probably due to the noxious effect of the released methanol. Anticancer drugs temozolomide and doxorubicin are encapsulated in the NPs with 20-40% efficiency, and their release is monitored using in vitro essays. Temozolomide is fully liberated within several hours, whereas doxorubicin is steadily released from the particles over a period of 1 month.

Nanobiopolymer for Direct Targeting and Inhibition of EGFR Expression in Triple Negative Breast Cancer

PloS One. 2012  |  Pubmed ID: 22355336

Treatment options for triple negative breast cancer (TNBC) are generally limited to cytotoxic chemotherapy. Recently, anti-epidermal growth factor receptor (EGFR) therapy has been introduced for TNBC patients. We engineered a novel nanobioconjugate based on a poly(β-L-malic acid) (PMLA) nanoplatform for TNBC treatment. The nanobioconjugate carries anti-tumor nucleosome-specific monoclonal antibody (mAb) 2C5 to target breast cancer cells, anti-mouse transferrin receptor (TfR) antibody for drug delivery through the host endothelial system, and Morpholino antisense oligonucleotide (AON) to inhibit EGFR synthesis. The nanobioconjugates variants were: (1) P (BioPolymer) with AON, 2C5 and anti-TfR for tumor endothelial and cancer cell targeting, and EGFR suppression (P/AON/2C5/TfR), and (2) P with AON and 2C5 (P/AON/2C5). Controls included (3) P with 2C5 but without AON (P/2C5), (4) PBS, and (5) P with PEG and leucine ester (LOEt) for endosomal escape (P/mPEG/LOEt). Drugs were injected intravenously to MDA-MB-468 TNBC bearing mice. Tissue accumulation of injected nanobioconjugates labeled with Alexa Fluor 680 was examined by Xenogen IVIS 200 (live imaging) and confocal microscopy of tissue sections. Levels of EGFR, phosphorylated and total Akt in tumor samples were detected by western blotting. In vitro western blot showed that the leading nanobioconjugate P/AON/2C5/TfR inhibited EGFR synthesis significantly better than naked AON. In vivo imaging revealed that 2C5 increased drug-tumor accumulation. Significant tumor growth inhibition was observed in mice treated with the lead nanobioconjugate (1) [P = 0.03 vs. controls; P<0.05 vs. nanobioconjugate variant (2)]. Lead nanobioconjugate (1) also showed stronger inhibition of EGFR expression and Akt phosphorylation than other treatments. Treatment of TNBC with the new nanobioconjugate results in tumor growth arrest by inhibiting EGFR and its downstream signaling intermediate, phosphorylated Akt. The nanobioconjugate represents a new generation of nanodrugs for treatment of TNBC.

Cellular Delivery of Doxorubicin Via PH-Controlled Hydrazone Linkage Using Multifunctional Nano Vehicle Based on Poly(β-L-Malic Acid)

International Journal of Molecular Sciences. 2012  |  Pubmed ID: 23109877

Doxorubicin (DOX) is currently used in cancer chemotherapy to treat many tumors and shows improved delivery, reduced toxicity and higher treatment efficacy when being part of nanoscale delivery systems. However, a major drawback remains its toxicity to healthy tissue and the development of multi-drug resistance during prolonged treatment. This is why in our work we aimed to improve DOX delivery and reduce the toxicity by chemical conjugation with a new nanoplatform based on polymalic acid. For delivery into recipient cancer cells, DOX was conjugated via pH-sensitive hydrazone linkage along with polyethylene glycol (PEG) to a biodegradable, non-toxic and non-immunogenic nanoconjugate platform: poly(β-l-malic acid) (PMLA). DOX-nanoconjugates were found stable under physiological conditions and shown to successfully inhibit in vitro cancer cell growth of several invasive breast carcinoma cell lines such as MDA-MB-231 and MDA-MB- 468 and of primary glioma cell lines such as U87MG and U251.

Distinct Mechanisms of Membrane Permeation Induced by Two Polymalic Acid Copolymers

Biomaterials. Jan, 2013  |  Pubmed ID: 23063368

Anionic polymers are valuable components used in cosmetics and health sciences, especially in drug delivery, because of their chemical versatility and low toxicity. However, because of their highly negative charge they pose problems for penetration through hydrophobic barriers such as membranes. We have engineered anionic polymalic acid (PMLA) to penetrate biological membranes. PMLA copolymers of leucine ethyl ester (P/LOEt) or trileucine (P/LLL) show either pH-independent or pH-dependent activity for membrane penetration. We report here for the first time on the mechanisms which are different for those two copolymers. Formation of hydrophobic patches in either copolymer is detected by fluorescence techniques. The copolymers display distinctly different properties in solution and during membranolysis. P/LOEt copolymer binds to membrane as single molecules with high affinity, and induces leakage cooperatively through a mechanism known as "carpet" model, in which the polymer aligns at the surface throughout the entire process of membrane permeation. In contrast, P/LLL self-assembles to form an oligomer of 105 nm in a pH-dependent manner (pKa 5.5) and induces membrane leakage through a two-phase process: the concentration dependent first-phase of insertion of the oligomer into membrane followed by a concentration independent second-phase of rearrangement of the membrane-oligomer complex. The insertion of P/LLL is facilitated by hydrophobic interactions between trileucine side chains and lipids in the membrane core, resulting in transmembrane pores, through mechanism known as "barrel-stave" model. The understanding of the mechanism paves the way for future engineering of polymeric delivery systems with optimal cytoplasmic delivery efficiency and reduced systemic toxicity.

Toxicity and Efficacy Evaluation of Multiple Targeted Polymalic Acid Conjugates for Triple-negative Breast Cancer Treatment

Journal of Drug Targeting. Dec, 2013  |  Pubmed ID: 24032759

Engineered nanoparticles are widely used for delivery of drugs but frequently lack proof of safety for cancer patient's treatment. All-in-one covalent nanodrugs of the third generation have been synthesized based on a poly(β-L-malic acid) (PMLA) platform, targeting human triple-negative breast cancer (TNBC). They significantly inhibited tumor growth in nude mice by blocking synthesis of epidermal growth factor receptor, and α4 and β1 chains of laminin-411, the tumor vascular wall protein and angiogenesis marker. PMLA and nanodrug biocompatibility and toxicity at low and high dosages were evaluated in vitro and in vivo. The dual-action nanodrug and single-action precursor nanoconjugates were assessed under in vitro conditions and in vivo with multiple treatment regimens (6 and 12 treatments). The monitoring of TNBC treatment in vivo with different drugs included blood hematologic and immunologic analysis after multiple intravenous administrations. The present study demonstrates that the dual-action nanoconjugate is highly effective in preclinical TNBC treatment without side effects, supported by hematologic and immunologic assays data. PMLA-based nanodrugs of the Polycefin™ family passed multiple toxicity and efficacy tests in vitro and in vivo on preclinical level and may prove to be optimized and efficacious for the treatment of cancer patients in the future.

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