Krishnendu Roy

Georgia Institute of Technology, Atlanta, Georgia, United States

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Publications (36)190.31 Total impact

  • Alberto Purwada, Krishnendu Roy, Ankur Singh
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    ABSTRACT: Controlled modulation of immune response, especially the balance between immunostimulatory and immunosuppressive responses is critical for a variety of clinical applications, including immunotherapies against cancer and infectious diseases, treatment of autoimmune disorders, transplant surgeries, regenerative medicine, prosthetic implants etc. Our ability to precisely modify both innate and adaptive immune responses could provide new therapeutic directions in a variety of diseases. In the context of vaccines and immunotherapies, the interplay between antigen presenting cells (e.g. dendritic cells and macrophages), B cells, T helper and killer subtypes, and regulatory T and B cell responses is critical for generating effective immunity against cancer, infectious diseases, and autoimmune diseases. In recent years, immunoengineering has emerged as a new field that uses quantitative engineering tools to understand molecular, cellular and systems-level interactions of the immune system and develop design-driven approaches to control and modulate immune-responses. Biomaterials are an integral part of this engineering tool-box and can exploit the intrinsic biological and mechanical cues of the immune system to directly modulate and train immune cells and direct their response to a particular phenotype. A large body of literature exists on strategies to evade or suppress the immune response in implants, transplantation and regenerative medicine, and has been discussed in several excellent reviews [1,2]. This review specifically focuses on the use of biomaterials for immunostimulation and controlled modulation, especially in the context of vaccines and immunotherapies against cancer, infectious diseases and autoimmune disorders. Bioengineering smart systems that can simultaneously deliver multiple bioactive agents in a controlled manner or can work as a niche for in situ priming and modulation of the immune system could significantly enhance the efficacy of next generation immunotherapeutics. In this review, we describe our perspective on the important design aspects for the development of biomaterials that can actively modulate immune responses by stimulating receptor complexes, cells, and delivering multiple immunomodulatory biomolecules.
    Acta biomaterialia 12/2013; · 5.09 Impact Factor
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    ABSTRACT: Size, surface charge, and material compositions are known to influence cell uptake of nanoparticles. However, the effect of particle geometry, i.e., the interplay between nanoscale shape and size, is less understood. Here we show that when shape is decoupled from volume, charge, and material composition, under typical in vitro conditions, mammalian epithelial and immune cells preferentially internalize disc-shaped, negatively charged hydrophilic nanoparticles of high aspect ratios compared with nanorods and lower aspect-ratio nanodiscs. Endothelial cells also prefer nanodiscs, however those of intermediate aspect ratio. Interestingly, unlike nanospheres, larger-sized hydrogel nanodiscs and nanorods are internalized more efficiently than their smallest counterparts. Kinetics, efficiency, and mechanisms of uptake are all shape-dependent and cell type-specific. Although macropinocytosis is used by both epithelial and endothelial cells, epithelial cells uniquely internalize these nanoparticles using the caveolae-mediated pathway. Human umbilical vein endothelial cells, on the other hand, use clathrin-mediated uptake for all shapes and show significantly higher uptake efficiency compared with epithelial cells. Using results from both upright and inverted cultures, we propose that nanoparticle internalization is a complex manifestation of three shape- and size-dependent parameters: particle surface-to-cell membrane contact area, i.e., particle-cell adhesion, strain energy for membrane deformation, and sedimentation or local particle concentration at the cell membrane. These studies provide a fundamental understanding on how nanoparticle uptake in different mammalian cells is influenced by the nanoscale geometry and is critical for designing improved nanocarriers and predicting nanomaterial toxicity.
    Proceedings of the National Academy of Sciences 10/2013; · 9.74 Impact Factor
  • Irina Fernandez, Tracy P Ooi, Krishnendu Roy
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    ABSTRACT: In vitro differentiation of mouse and human stem cells into early T cells has been successfully demonstrated using artificial Notch signaling systems. However, generation of mature, antigen-specific, functional T cells, directly from human stem cells has remained elusive, except when using stromal co-culture of stem cells retrovirally transfected with antigen-specific T cell receptors (TCRs). Here we show that human umbilical cord blood (UCB)-derived CD34+CD38-/low hematopoietic stem cells (HSCs) can be successfully differentiated into functional, antigen-specific cytotoxic CD8+ T cells without direct stromal co-culture or retroviral TCR transfection. Surface-immobilized Notch ligands (DLL1) and stromal cell conditioned medium successfully induced the development of CD1a+CD7+ and CD4+CD8+ early T cells. These cells, upon continued culture with cytomegalovirus (CMV) or Influenza-A virus epitope-loaded HLA-A*0201 tetramers, resulted in the generation of a polyclonal population of CMV-specific or Influenza-specific CD8+ T cells respectively. Upon further activation with antigen-loaded target cells, these antigen-specific, stem cell-derived T cells exhibited cytolytic functionality, specifically CD107a surface mobilization, IFNγ production, and Granzyme B secretion. Such scalable, in vitro generation of functional, antigen-specific human T cells from human stem cells could eventually provide a readily available cell source for adoptive transfer immunotherapies and also allow better understanding of human T cell development. Stem Cells 2013.
    Stem Cells 08/2013; · 7.70 Impact Factor
  • Rachit Agarwal, Krishnendu Roy
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    ABSTRACT: Recent progress in drug discovery has enabled the targeting of specific intracellular molecules to achieve therapeutic effects. These next-generation therapeutics are often biologics that cannot enter cells by mere diffusion. Therefore, it is imperative that drug carriers are efficiently internalized by cells and reach specific target organelles before releasing their cargo. Nanoscale polymeric carriers are particularly suitable for such intracellular delivery. Although size and surface charge have been the most studied parameters for nanocarriers, it is now well appreciated that other properties, for example, particle shape, elasticity and surface composition, also play a critical role in their transport across physiological barriers. It is proposed that a multivariate design space that considers the interdependence of particle geometry with its mechanical and surface properties must be optimized to formulate drug nanocarriers for effective accumulation at target sites and efficient intracellular delivery.
    Therapeutic delivery 06/2013; 4(6):705-23.
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    ABSTRACT: There is increasing interest in fabricating shape-specific polymeric nano- and microparticles for efficient delivery of drugs and imaging agents. The size and shape of these particles could significantly influence their transport properties and play an important role in in vivo biodistribution, targeting, and cellular uptake. Nanoimprint lithography methods, such as jet-and-flash imprint lithography (J-FIL), provide versatile top-down processes to fabricate shape-specific, biocompatible nanoscale hydrogels that can deliver therapeutic and diagnostic molecules in response to disease-specific cues. However, the key challenges in top-down fabrication of such nanocarriers are scalable imprinting with biological and biocompatible materials, ease of particle-surface modification using both aqueous and organic chemistry as well as simple yet biocompatible harvesting. Here we report that a biopolymer-based sacrificial release layer in combination with improved nanocarrier-material formulation can address these challenges. The sacrificial layer improves scalability and ease of imprint-surface modification due to its switchable solubility through simple ion exchange between monovalent and divalent cations. This process enables large-scale bionanoimprinting and efficient, one-step harvesting of hydrogel nanoparticles in both water- and organic-based imprint solutions.
    ACS Nano 03/2012; 6(3):2524-31. · 12.06 Impact Factor
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    ABSTRACT: In vitro bioreactor-based cultures are being extensively investigated for large-scale production of differentiated cells from embryonic stem cells (ESCs). However, it is unclear whether in vitro ESC-derived progenitors have similar gene expression profiles and functionalities as their in vivo counterparts. This is crucial in establishing the validity of ESC-derived cells as replacements for adult-isolated cells for clinical therapies. In this study, we compared the gene expression profiles of Lin-ckit+Sca-1+ (LKS) cells generated in vitro from mouse ESCs using either static or bioreactor-based cultures, with that of native LKS cells isolated from mouse fetal liver (FL) or bone marrow (BM). We found that in vitro-generated LKS cells were more similar to FL- than to BM LKS cells in gene expression. Further, when compared to cells derived from bioreactor cultures, static culture-derived LKS cells showed fewer differentially expressed genes relative to both in vivo LKS populations. Overall, the expression of hematopoietic genes was lower in ESC-derived LKS cells compared to cells from BM and FL, while the levels of non-hematopoietic genes were up-regulated. In order to determine if these molecular profiles correlated with functionality, we evaluated ESC-derived LKS cells for in vitro hematopoietic-differentiation and colony formation (CFU assay). Although static culture-generated cells failed to form any colonies, they did differentiate into CD11c+ and B220+ cells indicating some hematopoietic potential. In contrast, bioreactor-derived LKS cells, when differentiated under the same conditions failed to produce any B220+ or CD11c+ cells and did not form colonies, indicating that these cells are not hematopoietic progenitors. We conclude that in vitro culture conditions significantly affect the transcriptome and functionality of ESC-derived LKS cells and although in vitro differentiated LKS cells were lineage negative and expressed both ckit and Sca-1, these cells, especially those obtained from dynamic cultures, are significantly different from native cells of the same phenotype.
    PLoS ONE 01/2012; 7(12):e51944. · 3.73 Impact Factor
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    ABSTRACT: Patients with malignant non-Hodgkin's lymphomas (NHL) of B-cell lineages relapse despite initial anti-tumor response to chemotherapy or antibody treatments. Failure to eliminate the tumor is often because of inadequate priming, low cell numbers and suboptimal phenotype of effector T cells. Here we describe a new biomaterial-based controlled-release paradigm to treat weakly immunogenic NHLs by in-situ amplifying the number of functional, antigen-specific T-helper 1 (Th1) cells following immunotherapy. An injectable, synthetic immune priming center (sIPC) consisting of an in-situ crosslinking, chemokine-carrying hydrogel and both DNA- and siRNA dual-loaded microparticles, is reported. This sIPC chemo attracts a large number of immature dendritic cells (DCs) at the site of administration and efficiently co-delivers both DNA antigens and interleukin-10 (IL10)-silencing siRNA to those cells. Using a murine model of A20 B cell lymphoma, we demonstrate that combination of DNA-antigen delivery and IL10 silencing, synergistically activate recruited immature DCs and cause a strong shift towards Th1 response while suppressing Th2 and Th17 cytokines. sIPC-based immunotherapy showed 45% more CD8+ cytotoxic T cell (CTL) response and 53% stronger CD4+ CTL activity compared to naked DNA vaccine. In addition, in-vivo sIPC immunization induced significant protection (p<0.01) against subsequent tumor challenge. Such a multi-modal, injectable system that simultaneously delivers chemokines, siRNA and DNA antigens to DCs marks a new approach to in-situ priming and modulation during immunotherapy and could provide effective vaccination strategies against cancers and infectious diseases.
    Journal of Controlled Release 06/2011; 155(2):184-92. · 7.63 Impact Factor
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    ABSTRACT: Recently a number of hydrogel-based micro-and nanoscale drug carriers have been reported including top down fabricated, highly monodisperse nanoparticles of specific sizes and shapes. One critical question on such approaches is whether in vivo swelling of the nanoparticles could considerably alter their geometry to a point where the potential benefit of controlling size or shape could not be realized. Little has been reported on experimental characterization of the swelling behavior of nanoscale hydrogel structures, and current theoretical understanding is largely based on bulk hydrogel systems. Using atomic force microscopy (AFM) and environmental scanning electron microscopy (ESEM) capsules, we have characterized the swelling behavior of nano-imprinted hydrogel particles of different sizes and aspect ratios. Our results indicate a size-dependent swelling which can be attributed to the effect of substrate constraint of as-fabricated particles, when the particles are still attached to the imprinting substrate. Numerical simulations based on a recently developed field theory and a nonlinear finite element method were conducted to illustrate the constraint effect on swelling and drying behavior of substrate-supported hydrogel particles of specific geometries, and compared closely with experimental measurements. Further, we present a theoretical model that predicts the size-dependent swelling behavior for unconstrained sub-micron hydrogel particles due to the effect of surface tension. Both experimental and theoretical results suggest that hydrogel swelling does not significantly alter the shape and size of highly crosslinked nanoscale hydrogel particles used in the present study.
    Soft Matter 03/2011; 7(6). · 3.91 Impact Factor
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    Jian Lin, Irina Fernandez, Krishnendu Roy
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    ABSTRACT: Patient-specific therapeutic cells derived from induced pluripotent stem (iPS) cells may bypass the ethical issues associated with embryonic stem (ES) cells and avoid potential immunological reactions associated with allogenic transplantation. It is critical, for the ultimate clinical applicability of iPS cell-derived therapies, to establish feeder-free cultures that ensure efficient differentiation of iPS cells into therapeutic progenitors. It is also necessary to understand if iPS cell-derived progenitors differ from those derived from ES cells. In this study, we compared the efficiency of three different feeder-free cultures for differentiating mouse iPS cells into ckit+sca1+ hematopoietic progenitor cells (HPCs) and compared how differentiation and functionality varies between ES and iPS cells. Our results indicated that both iPS and ES cells can be efficiently differentiated into HPCs in suspension cultures supplemented with secretion factors from mouse bone marrow stromal cells (OP9-DL1 conditioned medium). The functionality of these cells was demonstrated by differentiation into CD11c+ dendritic cells (DCs). Both ES and iPS-derived DCs expressed activation molecules (CD86, CD80) in response to LPS stimulation and stimulated T cell proliferation in a mixed lymphocyte reaction (MLR). Extensive quantitative RT-PCR studies were used to study the differences in gene expression profiles of ckit+sca1+ cells generated from the various culture systems as well as differences between ES-derived and iPS-derived cells. We conclude that a feeder-free system using stromal conditioned medium can efficiently generate HPCs as well as functional DCs from iPS cells and the generated cells have similar gene expression profile as those from ES cells.
    Stem cell reviews 12/2010; 7(3):736-47. · 5.08 Impact Factor
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    ABSTRACT: Embryonic stem (ES)-cell-derived lineage-specific stem cells, for example, hematopoietic stem cells, could provide a potentially unlimited source for transplantable cells, especially for cell-based therapies. However, reproducible methods must be developed to maximize and scale-up ES cell differentiation to produce clinically relevant numbers of therapeutic cells. Bioreactor-based dynamic culture conditions are amenable to large-scale cell production, but few studies have evaluated how various bioreactor types and culture parameters influence ES cell differentiation, especially hematopoiesis. Our results indicate that cell seeding density and bioreactor speed significantly affect embryoid body formation and subsequent generation of hematopoietic stem and progenitor cells in both stirred tank (spinner flask) and rotary microgravity (Synthecon™) type bioreactors. In general, high percentages of hematopoietic stem and progenitor cells were generated in both bioreactors, especially at high cell densities. In addition, Synthecon bioreactors produced more sca-1(+) progenitors and spinner flasks generated more c-Kit(+) progenitors, demonstrating their unique differentiation profiles. cDNA microarray analysis of genes involved in pluripotency, germ layer formation, and hematopoietic differentiation showed that on day 7 of differentiation, embryoid bodies from both bioreactors consisted of all three germ layers of embryonic development. However, unique gene expression profiles were observed in the two bioreactors; for example, expression of specific hematopoietic genes were significantly more upregulated in the Synthecon cultures than in spinner flasks. We conclude that bioreactor type and culture parameters can be used to control ES cell differentiation, enhance unique progenitor cell populations, and provide means for large-scale production of transplantable therapeutic cells.
    Tissue Engineering Part A 11/2010; 16(11):3285-98. · 4.64 Impact Factor
  • Ankur Singh, Krishnendu Roy
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    ABSTRACT: T cell development from hematopoietic stem cells takes place in the thymus under precisely controlled intercellular signaling between the stem cells and thymic stromal and epithelial cells. In vitro or ex vivo development of mature T cells from stem cells faces two primary hurdles; one being the inability of culture conditions to provide a three dimensional thymic niche with lineage-specific signaling like notch, and the second being the need for efficient positive or negative selection processes to achieve antigen-specific, functional T cells. Recent research has focused on development of 2D and 3D niches mimicking the thymic microenvironment by first identifying soluble or immobilized factors essential for T cell differentiation followed by presenting them efficiently to stem and progenitor cells. This chapter discusses how T cells are generated in the thymus and current approaches, including biomaterial-based strategies, towards ex vivo or in vitro differentiation of stem cells into T cells using signaling molecules.
    06/2010: pages 225-245;
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    ABSTRACT: Despite high specificity and potency, small interfering RNA (siRNA)-based therapeutics have been limited by their poor biostability and intracellular penetration. Thus, effective nanocarriers that can protect and efficiently deliver siRNA to target cells in vivo are needed. Here we report on the efficiency of imidazole-modified chitosan (chitosan-imidazole-4-acetic acid [IAA])-siRNA nanoparticles to mediate gene silencing after administration via either intravenous (i.v.) or intranasal (i.n.) routes. Poly(ethylene glycol) (PEG)ylated nanoparticles for i.v. delivery demonstrated significant knockdown of glyceraldehyde 3-phosphate dehydrogenase (GAPDH) enzyme in both lung and liver at as low as 1 mg/kg siRNA dose. In addition, the efficient, dose-dependent silencing of apolipoprotein B in the liver was also shown. For i.n. delivery, significant silencing of GAPDH protein expression was seen in the lungs with only 0.5 mg/kg/day siRNA delivered over 3 consecutive days. In summary, imidazole-modified chitosan-IAA nanoparticles are potentially effective carriers for siRNA delivery.
    Oligonucleotides 06/2010; 20(3):163-72. · 2.75 Impact Factor
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    Jian Lin, Hui Nie, Phillip W Tucker, Krishnendu Roy
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    ABSTRACT: Generation of early T cells by coculturing stem cells on notch-ligand-expressing OP9 stromal cells (OP9-DL1) has been widely reported. However, further differentiation of these cells into mature, antigen-specific, functional T cells, without retroviral transduction of T cell receptors (TcRs), is yet to be achieved. In the thymic niche this differentiation is controlled by the interaction of developing TcRs with major histocompatibility (MHC) molecules on stromal cells. We hypothesized that by providing exogenous antigen-specific MHC/TcR signals, stem and progenitor cells could be engineered into functional, effector T cells specific for the same antigen. Here we demonstrate that both thymus-derived immature T cells (double positive [DP]: CD4+CD8+) and mouse embryonic stem cells can be efficiently differentiated into antigen-specific CD8+ T cells using either MHC tetramers or peptide-loaded stromal cells. DP cells, following MHC/TcR signaling, retained elevated recombination activating gene-1 levels, suggesting continuing TcR gene rearrangement. Both DP and embryonic stem-cell-derived CD8+ T cells showed significant cytotoxic T lymphocytes activity against antigen-loaded target cells, indicating that these cells are functional. Such directed differentiation strategy could provide an efficient method for generating functional, antigen-specific T cells from stem cells for potential use in adoptive T cell therapy.
    Tissue Engineering Part A 04/2010; 16(9):2709-20. · 4.64 Impact Factor
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    ABSTRACT: Although significant progress has been made in delivering therapeutic agents through micro and nanocarriers, precise control over in vivo biodistribution and disease-responsive drug release has been difficult to achieve. This is critical for the success of next generation drug delivery devices, as newer drugs, designed to interfere with cellular functions, must be efficiently and specifically delivered to diseased cells. The chief constraint in achieving this has been our limited repertoire of particle synthesis methods, especially at the nanoscale. Recent developments in generating shape-specific nanocarriers and the potential to combine stimuli-responsive release with nanoscale delivery devices show great promise in overcoming these limitations. How recent advances in fabrication technology allow synthesis of highly monodisperse, stimuli-responsive, drug-carrying nanoparticles of precise geometries is discussed. How particle properties, specifically shape and stimuli responsiveness, affect biodistribution, cellular uptake and drug release is also reviewed. The reader is introduced to recent developments in intelligent drug nanocarriers and new nanofabrication approaches that can be combined with disease-responsive biomaterials. This will provide insight into the importance of controlling particle geometry and incorporating stimuli-responsive materials into drug delivery. The integration of responsive biomaterials into shape-specific nanocarriers is one of the most promising avenues towards the development of next generation, advanced drug delivery systems.
    Expert Opinion on Drug Delivery 04/2010; 7(4):479-95. · 4.87 Impact Factor
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    Ankur Singh, Shalu Suri, Krishnendu Roy
    Biomaterials 02/2010; 31(6):1460. · 7.60 Impact Factor
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    ABSTRACT: The clinical applicability of antibodies and plasmonic nanosensors as topically applied, molecule-specific optical diagnostic agents for noninvasive early detection of cancer and precancer is severely limited by our inability to efficiently deliver macromolecules and nanoparticles through mucosal tissues. We have developed an imidazole-functionalized conjugate of the polysaccharide chitosan (chitosan-IAA) to enhance topical delivery of contrast agents, ranging from small molecules and antibodies to gold nanoparticles up to 44 nm in average diameter. Contrast agent uptake and localization in freshly resected mucosal tissues was monitored using confocal microscopy. Chitosan-IAA was found to reversibly enhance mucosal permeability in a rapid, reproducible manner, facilitating transepithelial delivery of optical contrast agents. Permeation enhancement occurred through an active process, resulting in the delivery of contrast agents via a paracellular or a combined paracellular/transcellular route depending on size. Coadministration of epidermal growth factor receptor-targeted antibodies with chitosan-IAA facilitated specific labeling and discrimination between paired normal and malignant human oral biopsies. Together, these data suggest that chitosan-IAA is a promising topical permeation enhancer for mucosal delivery of optical contrast agents.
    Journal of Biomedical Optics 01/2010; 15(1):015003. · 2.88 Impact Factor
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    Ankur Singh, Shalu Suri, Krishnendu Roy
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    ABSTRACT: Polymer-based, injectable systems that can simultaneously deliver multiple bioactive agents in a controlled manner could significantly enhance the efficacy of next generation therapeutics. For immunotherapies to be effective, both prophylactically or therapeutically, it is not only critical to drive the antigen (Ag)-specific immune response strongly towards either T helper type 1 (Th1) or Th2 phenotype, but also to promote recruitment of a high number of antigen-presenting cells (APCs) at the site of immunization. We have recently reported a microparticle-based system capable of simultaneously delivering siRNA and DNA to APCs. Here we present an in-situ crosslinkable, injectable formulation containing dendritic cell (DC)-chemo-attractants and dual-mode DNA-siRNA loaded microparticles to attract immature DCs and simultaneously deliver, to the migrated cells, immunomodulatory siRNA and plasmid DNA antigens. These low crosslink density hydrogels were designed to degrade within 2-7 days in vitro and released chemokines in a sustained manner. Chemokine carrying gels attracted 4-6 folds more DCs over a sustained period in vitro, compared to an equivalent bolus dose. Interestingly, migrated DCs were able to infiltrate the hydrogels and efficiently phagocytose the siRNA-DNA carrying microparticles. Hydrogel embedded microparticles co-delivering Interleukin-10 siRNA and plasmid DNA antigens exhibited efficient Interleukin-10 gene knockdown in migrated primary DCs in vitro.
    Biomaterials 07/2009; 30(28):5187-200. · 7.60 Impact Factor
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    ABSTRACT: Controlled modulation of T-cell response during immunotherapy, especially the balance between T helper 1 (Th1) and Th2 responses, is critical for generating effective immune response. Here we report that dual delivery of interleukin 10 (IL-10)-targeted small interfering RNA (siRNA) and DNA vaccines to dendritic cells (DCs), using a single particle carrier, efficiently enhances immune response and modulates it toward a stronger Th1 phenotype. Surface-functionalized polymer microparticles (MPs) carrying both IL-10-targeted siRNA and DNA antigens exhibited effective gene silencing, DNA transfection, and synergistically enhanced upregulation of maturation markers in primary DCs leading to increased T-cell proliferation, in vitro. Mice immunized with these dual-delivery carriers demonstrated a significant "switch" toward Th1 response as evidenced by increase in interferon gamma (IFN-gamma) production and decrease in IL-4 production by CD4+ T cells. This further led to enhanced antiviral cytotoxic T-lymphocyte activity. Such dual siRNA-DNA delivery provides a novel strategy to precisely control the type and strength of T-cell response during immunotherapy.
    Molecular Therapy 10/2008; 16(12):2011-21. · 7.04 Impact Factor
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    ABSTRACT: Our ability to precisely manipulate size, shape and composition of nanoscale carriers is essential for controlling their in-vivo transport, bio-distribution and drug release mechanism. Shape-specific, "smart" nanoparticles that deliver drugs or imaging agents to target tissues primarily in response to disease-specific or physiological signals could significantly improve therapeutic care of complex diseases. Current methods in nanoparticle synthesis do not allow such simultaneous control over particle size, shape and environmentally-triggered drug release, especially at the sub 100 nm range. We report here a high-throughput nanofabrication technique using synthetic and biological macromers (peptides) to produce highly monodisperse, enzymatically-triggered nanoparticles of precise sizes and shapes. Particles as small as 50 nm were fabricated on silicon wafers and harvested directly into aqueous buffers using a biocompatible, one-step release technique. We further demonstrate successful encapsulation and precisely controlled enzyme-triggered release of antibodies and nucleic acids from these nanoparticles, thus providing a potential means for disease-controlled delivery of biomolecules.
    Journal of Controlled Release 03/2008; 125(3):263-72. · 7.63 Impact Factor
  • Bilal Ghosn, Sudhir Pai Kasturi, Krishnendu Roy
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    ABSTRACT: Chitosan is a polysaccharide that has generated significant interest as a non-viral gene delivery vehicle due to its cationic and biocompatible characteristics. However, transfection efficiency of chitosan is significantly lower compared to other cationic gene delivery agents, e.g. polyethyleneimine (PEI), dendrimers or cationic lipids. This is primarily attributed to its minimal solubility and low buffering capacity at physiological pH leading to poor endosomal escape of the gene carrier and inefficient cytoplasmic decoupling of the complexed nucleic acid. Here we have developed an imidazole acetic acid (IAA)-modified chitosan to introduce secondary and tertiary amines to the polymer in order to improve its endosomal buffering and solubility. The modified polymer was characterized by ninhydrin and (1)H NMR assays for degree of modification, while buffering and solubility were analyzed by acid titration. Nanocomplex formation, studied at various polymer-nucleic acid ratios, showed an increase in particle zeta potential for chitosan-IAA, as well as an increase in the effective diameter. Up to 100-fold increase in transfection efficiency of pDNA was seen for chitosan-IAA as compared to native chitosan, nearly matching that of PEI. In addition, transfection of siRNA by the modified polymers showed efficient gene knockdown equivalent to commercially available siPORT Amines. Collectively, these results demonstrate the potential of the imidazole-grafted chitosan as a biocompatible and effective delivery vehicle for both pDNA and siRNA.
    Current topics in medicinal chemistry 02/2008; 8(4):331-40. · 4.47 Impact Factor