Browsing by Author "Varma, H K"
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Item Cell patch seeding and functional analysis of cellularized scaffolds for tissue engineering.(Biomedical materials (Bristol, England), 2007)Cell seeding has a direct impact on the final structure and function of tissue constructs, especially for applications like tissue engineering and regeneration. In this study seeding cell patches retrieved from the thermoresponsive poly(N-isopropylacrylamide) surface were used to generate in vitro tissue constructs. Porous and dense bone substitute materials were cellularized using osteoblast cells by a patch transfer and a trypsin method. The function and proliferation of cells was analyzed after 7 days of culture. The relative cell growth rate was found to be higher in cellularized porous hydroxyapatite (PHA) than in dense hydroxyapatite. Live-dead staining confirmed viable cells inside the pores of PHA. Increased alkaline phosphatase activity of cells transferred by the cell patch over the trypsin method revealed the significance of cell patch seeding. This novel method of generating tissue constructs by cell patch seeding was successful in cellularizing scaffolds with intact cell function.Item Fully injectable calcium phosphate cement--a promise to dentistry.(Indian journal of dental research : official publication of Indian Society for Dental Research, 2004)Calcium phosphate cements (CPC) are self setting and biocompatible bone substitute materials with potential applications in dentistry. However, its clinical use has been challenged by poor rheological properties. A novel formulation of CPC has been developed, which gives a fully injectable and cohesive paste. This work investigates the suitability of the new "fully injectable calcium phosphate cement" (FI-CPC) for dental applications. The cementing properties, material characteristics, and the rheological properties were tested using a battery of material characteristics methods. The biocompatibility was also evaluated as per ISO 7405. The setting time (20 min) and compressive strength (>11 Mpa) of FI-CPC satisfy the clinical requirements. It underwent setting without any exothermic reaction, keeping good dimensional stability. The cement paste could be extruded through a 18-gauge needle, easily and fully. It showed excellent cohesion when immersed in water. FI-CPC was seen to set into a micro-porous mass of hydroxyapatite, the mineral part of human dentin. It showed good attachment to dentin walls, when filled in tooth perforations. FI-CPC was found non-toxic, non-allergic, non-pyrogenic, and soft-tissue compatible. The study shows that FI-CPC provides a self setting bio-compatible paste with excellent rheological properties for surgical applications. The set cement provides good and stable sealing. The osteoconductive property is an added advantage. FI-CPC proves to be an ideal material for endodontic sealing/filling and periodontic repair.Item In vitro investigations of bone remodeling on a transparent hydroxyapatite ceramic.(Biomedical materials (Bristol, England), 2009)The light microscopic examination of cells directly on bioceramic materials in the transmission mode is impossible because many of these materials are opaque. In order to enable direct viewing of living cells and to perform time-lapse studies, nearly transparent bioceramic materials were developed. A dense and fine-grained transparent hydroxyapatite (tHA) was processed by a gel-casting route followed by low-temperature sintering (1000 degrees C). By virtue of its transparency, direct visualization of cellular events on this material is possible in transmitted light. In this study, the interaction of different bone cell types with the tHA ceramic was envisaged. Investigation of rat calvaria osteoblasts (RCO) cultured on tHA by means of transmission light microscopy indicated good cytocompatibility of tHA. Microscopic analysis of osteogenic-induced human bone marrow stromal cells (hBMSC) on tHA and quantitative analysis of their lactate dehydrogenase (LDH) activity at different time points of culture revealed favorable proliferation as well. An increase of the alkaline phosphatase (ALP) activity indicated the differentiation of osteogenic-induced hBMSC towards the osteoblastic lineage. In addition, the differentiation of human monocytes to osteoclast-like cells could also be demonstrated on tHA and was confirmed by fluorescent microscopy imaging of multinucleated cells on the transparent material.Item Rapid and complete cellularization of hydroxyapatite for bone tissue engineering.(Acta biomaterialia, 2005)Using a tissue construct generated by cells in a scaffold in reconstructive surgery, as a substitute for autografts, is still challenging. Routine methods of incorporating cells into scaffolds are either passive, i.e. by gravity, or forced, as in a bioreactor. Extensive use of these methods is obstructed by tissue formation around the scaffold, hindrance in cell penetration and time required for cell coverage within the scaffold. In this study, human osteoblast cells as cell sheet structures were seeded to porous and dense hydroxyapatite with the hypothesis that preservation of native extracellular structures and cell-cell contacts would facilitate the cellularization process. Cellularization was assessed by fluorescence, confocal and scanning electron microscopy at intervals of 1 h, 2 days and 7 days. Cell patches with intact cell-cell and cell-extra cellular matrix contact attached and adhered on a scaffold within 1 h. The patches formed a monolayer within 2 days and complete cellularization of the scaffold was attained in 7 days. Cell viability, proliferation and function were assessed to understand the application of cell patch transfer to bone substitute. This novel approach for application in bone tissue engineering was successful in uniform distribution of intact osteoblast cell sheet structures on to bone substitute materials for rapid and complete cellularization without altering material characteristics.Item Short-term studies using ceramic scaffolds in lapine model for osteochondral defect amelioration.(Biomedical materials (Bristol, England), 2012)This study was undertaken to glean preliminary information on the role of triphasic ceramic coated hydroxyapatite (HASi) and biphasic (alpha-tricalcium phosphate and hydroxyapatite based) calcium phosphate (BCP) for the development of osteochondral constructs. The proposed constructs were tested for performance in vitro with rabbit adipose-derived mesenchymal stem cells (RADMSCs) and further analysed in vivo in a lapine model for osteochondral defect amelioration. Desirable scaffolding architecture ensuring favourable conditions for cell attachment, nutrient exchange and neo-tissue organization was achieved by the synthesis of porous ceramic blocks and characterizations were carried out using x-ray diffraction and Fourier transform infrared spectroscopy. The cytocompatibility of the scaffold-cell combination product was evaluated using microscopy techniques that proved the scaffold to be non-cytotoxic and favourable for cell growth and proliferation. Short-term implantation studies were conducted with bare cylindrical HASi and BCP scaffolds, press fit deep into the bony bed of the median femoral condyles of the rabbit, which resulted in favourable specific in vivo response of de novo cartilage-like cells on the surface and sub-surface bony trabeculae. The generated pilot data will help to assess the severity of proposed procedures before embarking on scaled-up efforts.Item Triphasic ceramic coated hydroxyapatite as a niche for goat stem cell-derived osteoblasts for bone regeneration and repair.(Journal of materials science. Materials in medicine, 2009)Current treatment strategies for the repair or replacement of bone use synthetic implants with stem cells and their progeny--a new approach to address unmet medical needs. This study has evaluated the effect of a silica-coated bioactive ceramic, namely HASi in comparison to hydroxyapatite (HA) on the adhesion, proliferation and osteogenic differentiation of goat bone marrow-derived mesenchymal stem cells in vitro in a prolonged culture of 28 days. The cellular activities were significantly enhanced on HASi signifying the role of silica to stimulate osteoblast cells. The fabrication of such a 'cell-ceramic construct using autologous MSCs' is aimed for the transplantation to a large bone defect site in the goat femur model which still remains a formidable challenge in Orthopedic surgery.