Browsing by Author "Kumar, TRS"

Now showing 1 - 5 of 5
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    A freeze-dried fibrin disc as a biodegradable drug release matrix
    (BIOLOGICALS, 2004)
    A fibrin clot loaded with soluble tetracycline (TET) was prepared and lyophilized to make discs of a size and shape to use as a drug delivery matrix. On subcutaneous implantation of these discs in mice, they were found to have degraded in 15 days as evidenced by gross and histological examination. The in vitro discharge kinetics of tetracycline from the disc into phosphate buffered saline (PBS) and human serum were compared. It was observed that the release rate of tetracycline from the matrix into serum remained steady from day I to day 12, maintaining sufficient concentration that may be required to control microbial growth in the medium. Two different concentrations of fibrinogen were used to fabricate discs denoted as FG200 and FG100, and in both cases the retention rate was comparable when the study medium was serum. In contrast, when suspended in PBS instead of serum, the delivery of the drug into the medium was found to be high for up to the 3rd day when a sharp decline in discharge was observed. The fibrinogen used is a factor that determines not only the longevity of discharge but also fibrinolysis. The degradation of the disc in vitro was visible when the discs were suspended in the buffer, and correspondingly fibrin degradation product (FDP) measured in the medium using an antibody-based assay system was high. Fibrin disc is haemostatic and biodegradable in vivo, and in vitro release of a small molecule at a controlled rate is demonstrated here. Hence, it may be a suitable candidate as a drug delivery implant for short-term use. (C) 2004 The International Association for Biologicals. Published by Elsevier Ltd. All rights reserved.
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    A stable matrix for generation of tissue-engineered nonthrombogenic vascular grafts
    (TISSUE ENGINEERING, 2002)
    The potential of freeze-dried fibrin glue (FG) in combination with growth factor (GF) and gelatin (GEL) is evaluated for use as a matrix for endothelialization of artificial vascular grafts made of polytetrafluoroethylene (PTFE, Teflon) and polyethyleneterephthalate (Dacron). Improved adhesion and proliferation of human umbilical vein endothelial cells are demonstrated on different substrates coated with the FG-GF/FG-GF-GEL mixture, compared with the respective bare surfaces. The strength of adhesion of endothelial cells on the coated matrices was found to be adequate to resist shear stress when monolayers were exposed to forces of flow in an in vitro parallel plate flow chamber. The monolayers maintained physiological nonthrombogenic character as evidenced by in vitro platelet adhesion and response to agonist measurements. Nitric oxide synthesis by cells grown on the study matrices was also found to be normal. Thus, the matrix composition and the coating technique, as presented here, can be easily applied to generate tissue-engineered biomaterials with a nonthrombogenic endothelial cell monolayer for cardiovascular implants. The freeze-drying of the coated matrix ensures prolonged stability and thus the materials can be stored in a ready-to-use state for endothelial cell sodding or seeding.
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    Endothelial cell growth factor (ECGF) enmeshed with fibrin matrix enhances proliferation of EC in vitro
    (BIOMATERIALS, 2001) Kumar, TRS; Krishnan, LK
    The vascular biomaterials that are currently used for clinical implants have been considered as poor substrates for human endothelial cell adhesion and spreading. Therefore, thrombotic occlusion is the predominant cause for the failure of small diameter vascular grafts made out of Dacron or Teflon. To reduce surface thrombogenicity of material surfaces used for vascular implants, in vitro seeding of endothelial cells using adhesive protein matrix is under evaluation in various laboratories. Evidences suggest that fibrin matrix is a suitable matrix for endothelial cell (EC) adhesion to the currently available vascular graft materials; however, poor proliferation of attached cells seems to be a major limitation. During this study we have also found that fibrin is a better matrix compared to gelatin to support cell attachment and spreading. However, the poor proliferation of initially attached human umbilical cord vein endothelial cell (HUVEC) necessitated modification of the matrix composition to get a monolayer within a limited period. Since fibrin can form a network of protein bundles, an effort is made to incorporate growth factors within the matrix. Endothelial cell growth factor (ECGF) isolated from bovine hypothalamus is immobilized on the surface with fibrin glue (FG) to promote proliferation of HUVEC. The results demonstrate that proteins with similar molecular weights as growth factors (GF) are retained within the matrix and released into the culture medium for 96 h, in quantities that would be sufficient to promote cell proliferation. When cells were seeded on the matrix composed with components of FG and ECGF, the HUVEC proliferated at a significantly higher rate compared to the cells on surfaces coated with gelatin or fibrin. The EC thus grown on the composite (FG + ECGF) resisted the shear stress as compared to the cells grown on gelatin. The HUVEC monolayer grown on the composite seems thromboresistant as adhesion and activation of platelets are negligible after platelet rich plasma is incubated with the monolayer for about 1 h with agitation. Therefore, the composite of fibrin and ECGF can be a suitable matrix for further evaluation of patients' autologous endothelial cell attachment and proliferation for clinical application. (C) 2001 Elsevier Science Ltd. All rights reserved.
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    Fibrin-mediated endothelial cell adhesion to vascular biomaterials resists shear stress due to flow
    (JOURNAL OF MATERIALS SCIENCE-MATERIALS IN MEDICINE, 2002)
    In vitro endothelial cell (EC) seeding onto biomaterials for blood-contacting applications can improve the blood compatibility of materials. Adhesive proteins adsorbed from serum that is supplemented with the culture medium intercede the initial cell adhesion and subsequent spreading on material surface during culture. Nevertheless, physical and chemical properties of vascular biomaterial surface fluctuate widely between materials resulting in dissimilarity in protein adsorption characteristics. Thus, a variation is expected in cell adhesion, growth and the ability of cell to resist shear stress when tissue engineering on to vascular biomaterials is attempted. This study was carried out with an objective to determine the significance of a matrix coating on cell adhesion and shear stress resistance when cells are cultured on materials such as polytetrafluoroethylene (PTFE, Teflon) and polyethyleneterephthalate (Dacron), ultra high molecular weight polyethylene (UHMWPE) and titanium (Ti), that are used for prosthetic devices. The study illustrates the distinction of EC attachment and proliferation between uncoated and matrix-coated surfaces. The cell attachment and proliferation on uncoated UHMWPE and titanium surfaces were not significantly different from matrix-coated surfaces. However, shear stress resistance of the cells grown on composite coated surfaces appeared superior compared to the cells grown on uncoated surface. On uncoated vascular graft materials, the cell adhesion was not supported by serum alone and proliferation was scanty as compared to matrix-coated surface. Therefore, coating of implant devices with a composite of adhesive proteins and growth factors can improve EC attachment and resistance of the cells to the forces of flow. (C) 2002 Kluwer Academic Publishers.
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    Growth of gold nanoparticles in human cells
    (LANGMUIR, 2005) Anshup; Venkataraman, JS; Subramaniam, C; Kumar, RR; Priya, S; Kumar, TRS; Omkumar, RV; John, A; Pradeep, T
    Gold nanoparticles of 20-100 nm diameter were synthesized within HEK-293 i human embryonic kidney), HeLa (human cervical cancer), SiHa (human cervical cancer), and SKNSH (human neuroblastoma) cells, Incubation of 1 mM tetrachloroaurate solution, prepared in phosphate buffered saline (PBS), pH 7.4, with human cells grown to similar to 80% confluency yielded systematic growth of nanoparticles over a period of 96 h. The cells, stained due to nanoparticle growth, were adherent to the bottom of the wells of the tissue culture plates, with their morphology preserved, indicating that the cell membrane was intact. Transmission electron microscopy of ultrathin sections showed the presence of nanoparticles within the cytoplasm and in the nucleus, the latter being much smaller in dimension. Scanning near field microscopic images confirmed the growth of large particles within the cytoplasm. Normal cells gave UV-visible signatures of higher intensity than the cancer cells. Differences in the cellular metabolism of cancer and noricancer cells were manifested, presumably in their ability to carry out the reduction process.