Browsing by Author "Nair, PD"

Now showing 1 - 20 of 43
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    A 3D biodegradable protein based matrix for cartilage tissue engineering and stem cell differentiation to cartilage
    (JOURNAL OF MATERIALS SCIENCE-MATERIALS IN MEDICINE, 2009) Mohan, N; Nair, PD; Tabata, Y
    A protein based 3D porous scaffold is fabricated by blending gelatin and albumin. The biomimetic biodegradable gelatin, promoted good cell adhesion and its hydrophilic nature enabled absorption of culture media. Albumin is proposed to serve as a nontoxic foaming agent and also helped to attain a hydrophobic-hydrophilic balance. The hydrophobic-hydrophilic balance and appropriate crosslinking of the scaffold avoided extensive swelling, as well as retained the stability of scaffold in culture medium for long period. The scaffold is found to be highly porous with open interconnected pores. The adequate swelling and mechanical property of the scaffold helped to withstand the loads imparted by the cells during in vitro culture. The scaffold served as a nontoxic material to monolayer of fibroblast cells and is found to be cell compatible. The suitability of scaffold for chondrocyte culture and stem cell differentiation to chondrocytes is further explored in this work. The scaffold provided appropriate environment for chondrocyte culture, resulting in deposition of cartilage specific matrix molecules that completely masked the pores of the porous scaffold. The scaffold promoted the proliferation and differentiation of mesenchymal stem cells to chondrocytes in presence of growth factors. The transforming growth factor, TGF beta 3 promoted better chondrogenic differentiation than its isoform TGF beta 1 in this scaffold.
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    A 3D biodegradable protein based matrix for cartilage tissue engineering and stem cell differentiation to cartilage (vol 20, pg 49, 2009)
    (JOURNAL OF MATERIALS SCIENCE-MATERIALS IN MEDICINE, 2014) Mohan, N; Nair, PD; Tabata, Y
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    A biodegradable and biocompatible PVA-citric acid polyester with potential applications as matrix for vascular tissue engineering
    (JOURNAL OF MATERIALS SCIENCE-MATERIALS IN MEDICINE, 2009) Thomas, LV; Arun, U; Remya, S; Nair, PD
    Unique elastomeric and biocompatible scaffolds were produced by the polyesterification of poly(vinyl alcohol) (PVA) and citric acid via a simple polycondensation reaction. The physicochemical characterization of the materials was done by Fourier Transform Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC), Thermogravimetric Analysis (TGA), mechanical and surface property analyses. The materials are hydrophilic and have viscoelastic nature. Biodegradable, non-cytotoxic materials that can be tailored into 3D scaffolds could be prepared in an inexpensive manner. This polyester has potential implications in vascular tissue engineering application as a biodegradable elastomeric scaffold.
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    A biodegradable in situ injectable hydrogel based on chitosan and oxidized hyaluronic acid for tissue engineering applications
    (CARBOHYDRATE POLYMERS, 2011) Nair, S; Remya, NS; Remya, S; Nair, PD
    An "in situ" biodegradable gel consisting of chitosan, glycerol phosphate (GP) and oxidized hyaluronic acid (HDA) were synthesised and characterized This is a two component hydrogel system where chitosan neutralized with GP resulted in instantaneous gelling when combined with HDA. The gels are cytocompatible and could be freeze dried to form porous scaffolds. The percentage porosity of the freeze-dried chitosan hyaluronic acid dialdehyde gels (CHDA) increased with increasing oxidation. Fibroblast cells seeded onto CHDA porous scaffolds adhered, proliferated and produced ECM components on the scaffold. Chondrocytes encapsulated in CHDA gels retained their viability and specific phenotypic characteristics. The gel material is hence proposed as a scaffold and encapsulating material for tissue engineering applications. (C) 2011 Elsevier Ltd. All rights reserved.
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    A simple and effective method for making multipotent/multilineage scaffolds with hydrophilic nature without any postmodification/treatment
    (COLLOIDS AND SURFACES B-BIOINTERFACES, 2016) Vaikkath, D; Anitha, R; Sumathy, B; Nair, PD
    A number of biodegradable and bioresorbable materials, as well as scaffold designs, have been experimentally and/or clinically studied for tissue engineering of diverse tissue types. Cell material responses are strongly dependent on the properties of the scaffold material. In this study, scaffolds based on polycaprolactone (PCL) and PCL blended with a triblock copolymer, Polycaprolactone-polytetrahydrofuran-polycaprolactone (PCL-PTHF-PCL) at different ratios were fabricated by electrospinning. Blending and electrospinning of the triblock copolymer with PCL generated a super hydrophilic scaffold, the mechanical and biological properties of which varied with the concentration of the triblock copolymer. The hydrophilicity of the electrospun scaffolds was determined by measurement of water-air contact angle. Cellular response to the electrospun scaffolds was studied by seeding two types of cells, L929 fibroblast cell line and rat mesenchymal stem cells (RMSC). We observed that the super hydrophilicity of the material did not prevent cell adhesion, while the cell proliferation was low or negligible for scaffolds containing higher amount of PCL-PTHF-PCL. Chondrogenic differentiation of RMSC was found to be better on the PCL blend containing 10% (w/v) of PCL-PTHF-PCL than the bare PCL. Our studies indicate that the cellular response is dependent on the biomaterial composition and highlight the importance of tailoring the scaffold properties for applications in tissue engineering and regenerative medicine. (C) 2015 Elsevier B.V. All rights reserved.
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    Biomimetic fiber assembled gradient hydrogel to engineer glycosaminoglycan enriched and mineralized cartilage: An in vitro study
    (JOURNAL OF BIOMEDICAL MATERIALS RESEARCH PART A, 2015) Mohan, N; Wilson, JJ; Joseph, D; Vaikkath, D; Nair, PD
    The study investigated the potential of electrospun fiber assembled hydrogel, with physical gradients of chondroitin sulfate (CS) and sol-gel-derived bioactive glass (BG), to engineer hyaline and mineralized cartilage in a single 3D system. Electrospun poly(caprolactone) (PCL) fibers incorporated with 0.1% w/w of CS (CSL) and 0.5% w/w of CS (CSH), 2.4% w/w of BG (BGL) and 12.5% w/w of BG (BGH) were fabricated. The CS showed a sustained release up to 3 days from CSL and 14 days from CSH fibers. Chondrocytes secreted hyaline like matrix with higher sulfated glycosaminoglycans (sGAG), collagen type II and aggrecan on CSL and CSH fibers. Mineralization was observed on BGL and BGH fibers when incubated in simulated body fluid for 14 days. Chondrocytes cultured on these fibers secreted a mineralized matrix that consisted of sGAG, hypertrophic proteins, collagen type X, and osteocalcin. The CS and BG incorporated PCL fiber mats were assembled in an agarose-gelatin hydrogel to generate a 3D hybrid scaffold. The signals in the fibers diffused and generated continuous opposing gradients of CS (chondrogenic signal) and BG (mineralization) in the hydrogel. The chondrocytes were encapsulated in hybrid scaffolds; live dead assay at 48 h showed viable cells. Cells maintained their phenotype and secreted specific extracellular matrix (ECM) in response to signals within the hydrogel. Continuous opposing gradients of sGAG enriched and mineralized ECM were observed surrounding each cell clusters on gradient hydrogel after 14 days of culture in response to the physical gradients of raw materials CS and BG. A construct with gradient mineralization might accelerate integration to subchondral bone during in vivo regeneration. (c) 2015 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 103A: 3896-3906, 2015.
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    Chitosan-Comb-graft-Polyethylene Glycol Monomethacrylate-Synthesis, Characterization, and Evaluation as a Biomaterial for Hemodialysis Applications
    (JOURNAL OF APPLIED POLYMER SCIENCE, 2009) Radhakumary, C; Nair, PD; Nair, CPR; Mathew, S
    Chitosan was reacted with "Polyethylene glycol monomethacrylate" (PEGm) using a redox initiation method. Different compositions were prepared by varying the relative amount of PEGm in the feed. A maximum of 88% yield with 320% grafting could be achieved. The graft copolymerization was confirmed by FTIR, thermal, and XRD studies. Higher graft % could be achieved as the monomer used is a macro monomer of PEG and the resultant graft is a comb-like polymer. Grafting with PEGm did not affect the thermal stability of chitosan film significantly, however, it resulted in a marginal increase in the tensile strength of the films in the dry state. The products showed much improved swelling at pH 7.4 and pH 1.98 compared to the virgin chitosan. The preliminary biocompatibility evaluation showed that the materials are blood compatible and non-cytotoxic. Though the permeability to low molecular weight solutes like creatinine and glucose was equal to or better than commercial cellulose membranes, the copolymer films expressed comparatively less permeability to these solutes initially, due to the crystalline domains of PEO grafts that impede the transport. On exposure in the medium, this effect is nullified culminating in better permeability. The crystallization of PEG grafts was very helpful in preventing the permeation of the high molecular weight solute albumin, the leakage of which above a certain limit is dangerous to the patient. (C) 2009 Wiley Periodicals, Inc. J Appl Polym Sci 114: 2873-2886, 2009
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    Chitosan-graft-poly(vinyl acetate) for hemodialysis applications
    (JOURNAL OF APPLIED POLYMER SCIENCE, 2012) Radhakumary, C; Nair, PD; Nair, CPR; Mathew, S
    Chitosan was graft copolymerized with vinyl acetate using ceric ammonium nitrate as the initiator. The chitosan-g-poly(vinyl acetate) (chitosan-g-PVAc) membranes were found to be blood compatible, noncytotoxic, and biodegradable. The physicochemical characterization of the membranes revealed that the membranes possess the synergistic effect of the natural-synthetic hybrids of chitosan and PVAc with excellent mechanical stability and tunable hydrophilic/hydrophobic characteristics. The permeation characteristics of chitosan-g-PVAc membranes for four different solutes creatinine, urea, glucose, and albumin was studied in vitro at 37 degrees C for assessment of the suitability of them as hemodialysis membranes. The studies showed that the membranes exhibit higher permeability to creatinine, urea, and glucose compared with the commercial cellulose membrane and are impermeable to the essential nutrient albumin. Hence, the need for the development of biocompatible, mechanically strong dialysis membranes could be addressed with the modification of chitosan through grafting with PVAc. Potential applications like artificial kidney, artificial pancreas, and so forth, are envisaged from these membranes. (c) 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012
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    Currently practised sterilization methods - Some inadvertent consequences
    (JOURNAL OF BIOMATERIALS APPLICATIONS, 1995)
    Currently used sterilization techniques such as ethylene oxide, gamma irradiation, and steam sterilization could introduce inadvertent consequences, especially in polymeric materials. These could have far-reaching effects on the biocompatibility of the materials. Some of these consequences are reviewed and a typical example of the effect of steam sterilization on the properties and biocompatibility of polyethylene terephthalate is discussed.
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    An electrospun citric acid modified polyvinyl alcohol scaffold for vascular tissue engineering
    (Journal of Bioactive and Compatible Polymers, 2019-05) Thomas, LV; Nair, PD
    The main aim of this study is to fabricate an electrospun citric acid modified polyvinyl alcohol polyester that is biodegradable with non-toxic by-products and can be used for the culture of vascular smooth muscle cells. In this study, we have optimized the conditions for the electrospinning process of this polyester. The fibre morphology was studied by scanning electron microscopy which indicated that the fibre diameter was optimum at a range of 200 to 700 µm at 5% concentration and flow rate of 0.3 mL/h. The membranes were characterized for the change in structural aspects at the molecular level. The results showed development of more crystalline domains on electrospinning. The surface characteristics were also explored. Cell culture studies confirmed that the electrospun scaffold supported the attachment and proliferation of smooth muscle cells, which was evident from the cell proliferation assay. Hence, the electrospun polyester scaffolds are non-toxic and biocompatible with vascular smooth muscle cells, and find promising potential as scaffolds for vascular tissue engineering
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    Electrospun PVA-PCL-HAB scaffold for Craniofacial Bone Regeneration
    (TISSUE ENGINEERING PART A, 2015) Prabha, RD; Kraft, DC; Melsen, B; Varma, H; Nair, PD; Kjems, J; Kassem, M
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    Engineering cartilage tissue interfaces using a natural glycosaminoglycan hydrogel matrix An in vitro study
    (MATERIALS SCIENCE & ENGINEERING C-MATERIALS FOR BIOLOGICAL APPLICATIONS, 2013) Remya, NS; Nair, PD
    Hydrogels are suitable matrices for cartilage tissue engineering on account of their resemblance to native extracellular matrix of articular cartilage and also considering its ease of application, they can be delivered to the defect site in a minimally invasive manner. In this study, we evaluate the suitability of a fast gelling natural biopolymer hydrogel matrix for articular cartilage tissue engineering. A hydrogel based on two natural polymers, chitosan and hyaluronic acid derivative was prepared and physicochemically characterized. Chondrocytes were then encapsulated within the hydrogel and cultured over a period of one month. Cartilage regeneration was assessed by histological, biochemical and gene expression studies. Chondrocytes maintained typical round morphology throughout the course of this investigation, indicating preservation of their phenotype with sufficient production of extracellular matrix and expression of typical chondrogenic markers Collagen type 2 and aggrecan. The results suggest that the natural polymer hydrogel matrix can be used as an efficient matrix for articular cartilage tissue engineering. (C) 2012 Elsevier B.V. All rights reserved.
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    Enhanced encapsulation of chondrocytes within a chitosan/hyaluronic acid hydrogel: a new technique
    (Biotechnol. Lett., 2014-05) Ramesh, S; Rajagopal, K; Vaikkath, D; Nair, PD; Madhuri, V
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    Enhanced Survival and Function of Islet-Like Clusters Differentiated from Adipose Stem Cells on a Three-Dimensional Natural Polymeric Scaffold: An In Vitro Study
    (TISSUE ENGINEERING PART A, 2014) Aloysious, N; Nair, PD
    Autologous adipose stem cells owing to its pluripotent nature offer a valuable source for pancreatic beta cell replacement in the treatment of diabetes mellitus. However, maintaining longevity and functionality of stem cell-derived islet-like cells for long-term in vitro culture is challenging. Signaling interaction between islets and surrounding extracellular matrix (ECM) is an important factor for islet survival and function. Tissue engineering strategy to use scaffolds as substitute for ECM is a key to the problem. In the present study, we fabricated a three-dimensional (3D) biodegradable scaffold comprised of natural polymers dextran and gelatin (DEXGEL) for differentiation of adipose stem cells to islet-like clusters (ILCs). Adipose stem cells derived from subcutaneous fat of New Zealand white rabbits were differentiated to ILCs on DEXGEL scaffold and two-dimensional (2D) culture plates via three stage protocol using cocktail of growth factors. The ILCs differentiated on DEXGEL scaffold exhibited characteristic islet morphology, and expressed islet-specific hormones (insulin, glucagon, and somatostatin). The insulin secretion in response to glucose challenge and viability of ILCs on DEXGEL scaffold were significantly higher in comparison to ILCs on 2D culture. Our results demonstrated for the first time that DEXGEL scaffold simulated an extracellular environment for effective differentiation of rabbit adipose stem cells to ILCs.
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    Fabrication of a microvesicles-incorporated fibrous membrane for controlled delivery applications in tissue engineering
    (BIOFABRICATION, 2014) Nair, BP; Vaikkath, D; Mohan, DS; Nair, PD
    A scaffold, which can provide mechanical support for tissue regeneration and simultaneously release functionally active biomolecules are highly desirable for tissue engineering applications. Herein, we report the fabrication of a fibrous mesh of polycaprolactone (PCL) incorporating PCL-pluronic (F127) microvesicles through electrospinning, by exploiting the slow dissolution of PCL in glacial acetic acid (g-AA). Micro-vesicles 1-10 mu m in diameter were fabricated through a non-solubility driven spontaneous self-assembly and stabilization of F127 with low molecular weight PCL in tetrahydrofuran-water mixture. Time-dependent stability of the vesicles in g-AA was confirmed prior to the electrospinning. The electrospun membrane was found to be comprised of microvesicles entangled in a fibrous mesh of PCL with a fiber diameter ranging from 50-300 nm. Significant reduction in the release rate of rhodamine-B, an indicator dye from the electrospun membrane, when compared to that from the vesicle alone, evidences the surface coating of the vesicles with high molecular weight PCL during electrospinning. The vesicle incorporated membrane exhibited increased hydrophilicity when compared to the control PCL membrane, possibly due to surface unevenness and the hydrophilic F127. This enhanced surface hydrophilicity led to an increased cell viability of L929 cells on the membrane.
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    Fabrication of a microvesicles-incorporated fibrous membrane for controlled delivery applications in tissue engineering.
    (Biofabrication., 2014-10) Nair, BP; Vaikkath, D; Mohan, DS; Nair, PD
    A scaffold, which can provide mechanical support for tissue regeneration and simultaneously release functionally active biomolecules are highly desirable for tissue engineering applications. Herein, we report the fabrication of a fibrous mesh of polycaprolactone (PCL) incorporating PCL-pluronic (F127) microvesicles through electrospinning, by exploiting the slow dissolution of PCL in glacial acetic acid (g-AA). Micro-vesicles 1-10 μm in diameter were fabricated through a non-solubility driven spontaneous self-assembly and stabilization of F127 with low molecular weight PCL in tetrahydrofuran-water mixture. Time-dependent stability of the vesicles in g-AA was confirmed prior to the electrospinning. The electrospun membrane was found to be comprised of microvesicles entangled in a fibrous mesh of PCL with a fiber diameter ranging from 50-300 nm. Significant reduction in the release rate of rhodamine-B, an indicator dye from the electrospun membrane, when compared to that from the vesicle alone, evidences the surface coating of the vesicles with high molecular weight PCL during electrospinning. The vesicle incorporated membrane exhibited increased hydrophilicity when compared to the control PCL membrane, possibly due to surface unevenness and the hydrophilic F127. This enhanced surface hydrophilicity led to an increased cell viability of L929 cells on the membrane.
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    Generation of Pancreatic Hormone-Expressing Islet-Like Cell Aggregates from Murine Adipose Tissue-Derived Stem Cells
    (STEM CELLS, 2009) Chandra, V; Swetha, G; Phadnis, S; Nair, PD; Bhonde, RR
    The success of cell replacement therapy for diabetes depends on the availability and generation of an adequate number of islets, preferably from an autologous origin. Stem cells are now being probed for the generation of physiologically competent, insulin-producing cells. In this investigation, we explored the potential of adipose tissue-derived stem cells (ASCs) to differentiate into pancreatic hormone-expressing islet-like cell aggregates (ICAs). We initiated ASC culture from epididymal fat pads of Swiss albino mice to obtain mesenchymal cells, murine epididymal (mE)-ASCs. Subsequent single-cell cloning resulted in a homogeneous cell population with a CD29(+)CD44(+)Sca1(+) surface antigen expression profile. We formulated a 10-day differentiation protocol to generate insulin-expressing ICAs from mE-ASCs by progressively changing the differentiation cocktail on day 1, day 3, and day 5. Our stagespecific approach successfully differentiated mesodermic mE-ASCs into definitive endoderm (cells expressing Sox17, Foxa2, GATA-4, and cytokeratin [CK]-19), then into pancreatic endoderm (cells expressing pancreatic and duodenal homeobox [PDX]-1, Ngn3, NeuroD, Pax4, and glucose transporter 2), and finally into cells expressing pancreatic hormones (insulin, glucagon, somatostatin). Fluorescence-activated cell sorting analysis showed that day 5 ICAs contained 64.84% +/- 7.03% PDX-1(+) cells, and in day 10 mature ICAs, 48.17% +/- 3% of cells expressed C-peptide. Day 10 ICAs released C-peptide in a glucose-dependent manner, exhibiting in vitro functionality. Electron microscopy of day 10 ICAs revealed the presence of numerous secretory granules within the cell cytoplasm. Calcium alginate-encapsulated day 10 ICAs (1,000-1,200), when transplanted i.p. into streptozotocin-induced diabetic mice, restored normoglycemia within 2 weeks. The data presented here demonstrate the feasibility of using ASCs as a source of autologous stem cells to differentiate into the pancreatic lineage. STEM CELLS 2009; 27: 1941-1953
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    Generation of Tevg using Ramsc Derived Rsmc Seeded on a Biomimetic Nano Fibrous Scaffold
    (TISSUE ENGINEERING PART A, 2015) Thottappillil, ND; Nair, PD