Browsing by Author "Varma, H. K."

Now showing 1 - 8 of 8
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    Bioinspired mineralization and cell adhesion on surface functionalized poly(vinyl alcohol) films
    (ACTA BIOMATERIALIA, 2009)
    Poly(vinyl alcohol) (PVA) films, when surface functionalized by phosphorylation, induced biomimetic nucleation and growth of calcium phosphate in a simulated physiological environment. The surface phosphorylation on PVA was ensured by attenuated total reflectance infrared spectroscopy. The morphology of the calcium phosphate phase grown on surface-phosphorylated PVA (PPVA) was analysed using scanning electron microscopy coupled with an energy-dispersive X-ray detector. The primary nucleation of calcium phosphate occurs in 3 days and secondary nucleation occurs after 10 days. The energy-dispersive X-ray analysis shows that the Ca/P ratio of the coating increases with time of exposure to the simulated physiological fluid and reaches 1.67 at 10 days. The PPVA supports in vitro cell adhesion and promotes in vitro biomineralization in the presence of cells, evaluated using human osteosarcoma cells. (C) 2008 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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    Cosmetic and radiological outcome following the use of synthetic hydroxyapatite porous-dense bilayer burr-hole buttons
    (ACTA NEUROCHIRURGICA, 2007)
    Background. Cranial neurosurgical procedures utilising burr-holes lead to development of cosmetically unacceptable puckered scars on the scalp over burr-hole sites. Ceramics, especially Hydroxyapatite (HA) are good bone substitutes owing to their biocompatibility and osteoconduction i.e. ability to lay down bone over the implant by fibrovascular invasion and later bone formation. The Sree Chitra Tirunal Institute for Medical Sciences and Technology in India has pioneered research in this direction and has developed a unique porous-dense bilayer HA burr-hole button. This study evaluates the safety, cosmetic effect, as well as the radiological outcome following implantation of these bilayer HA buttons.Method. Sixty-five HA buttons were implanted in 22 patients who underwent cranial neurosurgical procedures at the Sree Chitra Tirunal Institute for Medical Sciences and Technology. We assessed the cosmetic outcome (absence of puckered scar over burr hole sites, absence of allergic reactions or infections associated with the implant) as well as the radiological outcome with X-rays at specified intervals and looked for interference in the postoperative neurological imaging due to the implants.Results. There were no adverse events related to the HA buttons in the form of allergic reactions or infections. The implants persisted as radio-dense opacities on skull X-rays of recipients for up to two years. It did not lead to artefacts on postoperative CT or MR imaging of the brain. In particular, the HA buttons could be subtracted on Digital Subtraction Angiography and did not obstruct visualisation of the cerebral vasculature.Conclusion. The bi-layer porous-dense HA buttons are useful in preventing cosmetic defects over burr-hole sites on the scalp after cranial neurosurgical procedures. It does not interfere with current radiological imaging methods in the postoperative phase.
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    Human osteosarcoma cell adhesion behaviour on hydroxyapatite integrated chitosan-poly(acrylic acid) polyelectrolyte complex
    (ACTA BIOMATERIALIA, 2006)
    A novel degradable composite system has been prepared by integrating hydroxyapatite, Ca-10(PO4)(6)(OH)(2), (HAP) in a polyelectrolyte complex matrix of chitosan (CHI) and poly(acrylic acid) (PAA). The composite was formulated by integrating 80 wt.% HAP in the polyelectrolyte complex matrix of CHI and PAA in the ratio 40/60 (designated as CPH). The composite could be easily fabricated into clinically significant shapes by a simple moulding procedure intended for bone graft applications. The adhesion behaviour of human osteosarcoma (HOS) cells on this degradable composite system was studied by selecting the polyelectrolyte complex, CHI/PAA 40/60 (designated as CP) as control sample. Light microscopic observations show that cells around CPH retained the typical morphology of HOS cells while cells around the polyelectrolyte complex showed a cytotoxic effect. The adhesion behaviour as well as morphological responses of the seeded cells was further investigated by scanning electron microscopy. The scanning electron micrographs of the polyelectrolyte complex, CP, showed the presence of rounded cells with raised nuclear regions, indicating delayed spreading; cells adhered on CPH were flattened with filopodia and showed good attachment and spreading, indicating better adhesion onto the HAP integrated composite. Comparing the MTT assay for quantitative evaluation of cell viability, CPH showed a higher percentage of metabolically active cells compared to CP. (c) 2006 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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    Hydroxyapatite moldable formulation using natural rubber latex as binder
    (JOURNAL OF BIOMEDICAL MATERIALS RESEARCH PART B-APPLIED BIOMATERIALS, 2007)
    A simple but efficient processing method for shaping intricate bioceramic green bodies has been developed by using natural rubber latex as binder. Different shapes of hydroxyapatite Ca-10(PO4)(6)(OH)(2) (HAP) were molded from a composite formulation containing wet precipitated HAP, natural rubber latex (NRL), and a stabilizer. On controlled heat treatment followed by sintering, dense shapes of HAP contours were obtained. The thermal degradation profile of HAP-NRL composites shows that NRL degrades slowly without any abrupt exotherm. The results of energy dispersive X-ray analysis together with inductively coupled plasma (ICP) analysis indicate that the inorganic residue of NRL does not contain any heavy element. The sintered density of the samples increased with increased HAP content in the formulation and percentage shrinkage reduced accordingly. On varying the HAP content in the formulation from 35 to 95 wt %, the compositions with 85, 90, 92, and 95 wt % HAP showed better flexural strength in the range 40-54 MPa and a flexural modulus value in the range 36-50 GPa. The fracture morphology, as observed by the scanning electron microscope confirms that with increased HAP content in the formulation the sample microstructure attains higher uniformity. The Vickers microhardness for the samples sintered at two different temperatures (1150 and 1250 degrees C) showed that hardness increases with increase in the sintering temperature with a maximum for the highest HAP loaded formulation. (c) 2006 Wiley Periodicals. Inc.
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    Platelet-Rich Plasma and Fibrin Glue-Coated Bioactive Ceramics Enhance Growth and Differentiation of Goat Bone Marrow-Derived Stem Cells
    (TISSUE ENGINEERING PART A, 2009)
    New biotechnologies such as tissue engineering require functionally active cells within supportive matrices where the physical and chemical stimulus provided by the matrix is indispensable to determine the cellular behavior. This study has investigated the influence of platelet-rich plasma (PRP) and fibrin glue (FG) on the functional activity of goat bone marrow-derived mesenchymal stem cells (gBMSCs) that differentiated into the osteogenic lineage. To achieve this goal, PRP and FG were separately coated on bioactive ceramics like hydroxyapatite (HA) and silica-coated HA (HASi), on which gBMSCs were seeded and induced to differentiate into the osteogenic lineage for 28 days. The cells were then analyzed for viability (lactate dehydrogenase assay: acridine orange and ethidium bromide staining), morphology (scanning electron microscopy), proliferation (picogreen assay), cell cycle assay (propidium iodide staining), and differentiation (alkaline phosphatase [ALP] activity and real-time PCR analysis of ALP, osteocalcin, and osteopontin gene). It has been observed that PRP and FG have appreciably favored the viability, spreading, and proliferation of osteogenic-induced gBMSCs. The osteopontin and osteocalcin expression was significantly enhanced on PRP- and FG-coated HA and HASi, but PRP had effect on neither ALP expression nor ALP activity. The results of this study have depicted that FG-coated ceramics were better than PRP- coated and bare matrices. Among all, the excellent performance was shown by FG coated HASi, which may be attributed to the communal action of the stimulus emanated by Si in HASi and the temporary extracellular matrix provided by FG over HASi. Thus, we can conclude that PRP or FG in combination with bioactive ceramics could possibly enhance the functional activity of cells to a greater extent, promoting the hybrid composite as a promising candidate for bone tissue engineering applications.
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    Reconstruction of goat femur segmental defects using triphasic ceramic-coated hydroxyapatite in combination with autologous cells and platelet-rich plasma
    (ACTA BIOMATERIALIA, 2009)
    Segmental bone defects resulting from trauma or pathology represent a common and significant clinical problem. In this study, a triphasic ceramic (calcium silicate, hydroxyapatite and tricalcium phosphate)-coated hydroxyapatite (HASi) having the benefits of both HA (osteointegration, osteoconduction) and silica (degradation) was used as a bone substitute for the repair of segmental defect (2 cm) created in a goat femur model. Three experimental goat femur implant groups - (a) bare HASi, (b) osteogenic-induced goat bone marrow-derived mesenchymal stem cells cultured HASi (HASi + C) and (c) osteogenic-induced goat bone marrow-derived mesenchymal stem cells cultured HASi + platelet-rich plasma (HASi + CP) - were designed and efficacy performance in the healing of the defect was evaluated. In all the groups, the material united with host bone without any inflammation and an osseous callus formed around the implant. This reflects the osteoconductivity of HASi where the cells have migrated from the cut ends of host bone. The most observable difference between the groups appeared in the mid region of the defect. In bare HASi groups, numerous osteoblast-like cells could be seen together with a portion of material. However, in HASi + C and HASi + CP, about 60-70% of that area was occupied by woven bone, in line with material degradation. The interconnected porous nature (50-500 mu m), together with the chemical composition of the HASi, facilitated the degradation of HASi, thereby opening up void spaces for cellular ingrowth and bone regeneration. The combination of HASi with cells and PRP was an added advantage that could promote the expression of many osteoinductive proteins, leading to faster bone regeneration and material degradation. Based on these results, we conclude that bare HASi can aid in bone regeneration but, with the combination of cells and PRP, the sequence of healing events are much faster in large segmental bone defects in weight-bearing areas in goats. (c) 2009 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved.
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    Tissue regeneration and repair of goat segmental femur defect with bioactive triphasic ceramic-coated hydroxyapatite scaffold
    (JOURNAL OF BIOMEDICAL MATERIALS RESEARCH PART A, 2009)
    Bone tissue engineering which is a developing and challenging field of science, is expected to enhance the regeneration and repair of bone lost from injury or disease and ultimately to gain its aesthetic contour. The objective of this study was to fabricate a tissue-engineered construct in vitro using a triphasic ceramic-coated hydroxypatite (HASi) in combination with stem cells and to investigate its potential in healing segmental defect in goat model. To accomplish this attempt, mesenchymal stern cells isolated from goat bone marrow were seeded onto HASi scaffolds and induced to differentiate into the osteogenic lineage in vitro. Scanning electron microscopy and light microscopy revealed adhesion and spread-out cells, which eventually formed a cell-sheet like canopy over the scaffold. Cells migrated and distributed themselves within the internal voids of the porous ceramic. Concurrently, the neoosteogenesis of the tissue-engineered construct was validated in vivo in comparison with bare HASi (without cells) in goat femoral diaphyseal segmental defect (2 cm) at 4 months postimplantation through radiography, computed tomography, histology, histomorphometry, scanning electron microscopy and inductively coupled plasma spectrometry. Good osteointegration and osteoconduction was observed in bare and tissue-engineered HASi. The performance of tissue-engineered HASi was better and faster which was evident by the lamellar bone organization of newly formed bone throughout the defect together with the degradation of the material. On the contrary with bare HASi, immature woven bony bridges still intermingled with scattered small remnants of the material was observed in the mid region of the defect at 4 months. Encouraging results from this preclinical study has proved the capability of the tissue-engineered HASi as a promising candidate for the reconstruction of similar bony defects in humans. (C) 2008 Wiley Periodicals, Inc. J Biomed Mater Res 91A: 855-865, 2009
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    Ultrastructural evaluation of in vitro mineralized calcium phosphate phase on surface phosphorylated poly(hydroxy ethyl methacrylate-co-methyl methacrylate)
    (JOURNAL OF MATERIALS SCIENCE-MATERIALS IN MEDICINE, 2010)
    The in vitro functionality of surface phosphorylated poly(hydroxy ethyl methacrylate-co-methyl methacrylate), poly(HEMA-co-MMA) to induce bioinspired mineralization of calcium phosphate phase is evaluated. The primary nucleation of calcium phosphate on the surface phosphorylated copolymer occurs within 3 days of immersion when immersed in 1.5x simulated body fluid and the degree of mineralization is proportional to the hydroxy ethyl methacrylate content in the copolymer. The calcium phosphate phase is identified as hydroxyapatite by X-Ray diffraction analysis. The transmission electron microscopic evaluation combined with selected area diffraction pattern and energy dispersive analysis exemplified that the primary nuclei of amorphous calcium phosphate transforms to crystalline needle like calcium rich apatite, within a period of 3 days immersion in simulated body fluid. The atomic force microscopic results corroborate the c-axis growth of the crystals within 3 days immersion in SBF.