Vinoy Thomas | University of Alabama at Birmingham (original) (raw)
Papers by Vinoy Thomas
Journal of Non-crystalline Solids, 2003
Materials Chemistry and Physics, 2003
Materials Chemistry and Physics, 2006
Solgel method is useful in the preparation of nanocrystallites-doped gel glasses with relatively... more Solgel method is useful in the preparation of nanocrystallites-doped gel glasses with relatively high particle concentrations, small particle diameter and uniform size distribution [1]. The solgel process allows incorporation of semiconductor nanocrystals along with rare earth ...
Journal of Photochemistry and Photobiology A-chemistry, 2002
Journal of Fluorescence, 2004
Silica glass samples containing CdSe/Eu3+ ions were prepared by sol-gel route. Size distribution ... more Silica glass samples containing CdSe/Eu3+ ions were prepared by sol-gel route. Size distribution and optical band gap of the nanoparticles were calculated from absorption spectrum. It is observed that the presence of CdSe nanocrystallites enhances the fluorescence of europium in silica glass. The phonon sideband spectrum associated with the excitation transition 7F0−5D2 is used to analyze the electron–phonon coupling and nonradiative deexcitiation of the rare earth ions in the glass host. The observed fluorescence enhancement is discussed on the basis of phonon assisted energy transfer from electron-hole recombination of the CdSe nanocrystallites to the rare earth ion and multiphonon relaxation.
Journal of Sol-gel Science and Technology, 2005
Silica glasses doped with Dy3+ were prepared by sol–gel method. The FTIR and thermo gravimetric a... more Silica glasses doped with Dy3+ were prepared by sol–gel method. The FTIR and thermo gravimetric analysis (TGA) clearly show complete densification (density = 2.2 gm/cm3) of the gels around 1000∘C. The fluorescence properties of Dy3+ ion are utilized to study the structural changes during the gel to glass transition of the silica xerogels. The fluorescence intensity and full width at half maximum (FWHM) of the emission bands show an increasing tendency with heat treatment. This is attributed to a glassy silica network with an asymmetric environment. The (Y/B) ratio for the Dy3+ ion is found to be less sensitive to site symmetry effects.
Journal of Physics and Chemistry of Solids, 2003
... PI Paulose a , G. Jose a , V. Thomas a , NV Unnikrishnan Corresponding Author Contact Informa... more ... PI Paulose a , G. Jose a , V. Thomas a , NV Unnikrishnan Corresponding Author Contact Information , E-mail The Corresponding Author , a and MKR Warrier b. a School of Pure and Applied Physics, Priyaddarshini Hills PO, Mahatma Gandhi University, Kottayam 686 560, India. ...
Journal of Biomedical Materials Research Part A, 2008
Development of new generation high flex life polyurethane urea (HFL18-PU) with appropriate elasti... more Development of new generation high flex life polyurethane urea (HFL18-PU) with appropriate elastic modulus, biocompatibility, blood compatibility, resistant to calcification, and biodurability for the long-term use as cardiac device is still a challenge. This study reports the development of a fully aliphatic, ether-free physically cross-linked and low elastic modulus (6.841 ± 0.27 MPa) polyurethane urea having in vivo biostability, in vivo biocompatibility and high flex-life (721 ± 30 million cycles) that can satisfy the requirements for the fabrication of tri-leaflet heart valve. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res, 2009
Journal of Biomaterials Applications, 2000
Polymer International, 2000
... Correspondence: Muthu Jayabalan, Sree Chitra Tirunal Institute for Medical Sciences and Techn... more ... Correspondence: Muthu Jayabalan, Sree Chitra Tirunal Institute for Medical Sciences and Technology ... Also we are grateful to Dr P Ramesh, Mr Roy Joseph, Mr Willi Paul and Mrs C Radhakumari for providing analytical help in the evaluation of the polymers. REFERENCES. ...
Biomacromolecules, 2001
The effect of physical cross-linking in candidate cycloaliphatic and hydrophobic poly(urethane ur... more The effect of physical cross-linking in candidate cycloaliphatic and hydrophobic poly(urethane urea) (4,4'-methylenebis(cyclohexylisocyanate), H(12)MDI/hydroxy-terminated polybutadiene, HTPBD/hexamethylenediamine, HDA) and poly(ether urethane urea)s (H(12)MDI/HTPBD-PTMG/HDA) on the in vitro calcification and blood-material interaction was studied. All the candidate poly(urethane urea)s and poly(ether urethane urea)s elicit acceptable hemolytic activity, cytocompatibility, calcification, and blood compatibility in vitro. The studies on blood-material interaction reveal that the present poly(urethane urea)s are superior to polystyrene microtiter plates which were used for the studies on blood-material interaction. The present investigation reveals the influence of physical cross-link density on biological interaction differently with poly(urethane urea) and poly(ether urethane urea)s. The higher the physical cross-link density in the poly(urethane urea)s, the higher the calcification and consumption of WBC in whole blood. On the other hand, the higher the physical cross-link density in the poly(ether urethane urea)s, the lesser the calcification and consumption of WBC in whole blood. However a reverse of the above trend has been observed with the platelet consumption in the poly(urethane urea)s and poly(ether urethane urea)s.
Journal of Biomedical Materials Research, 2001
The effect of virtual crosslinking on the hydrolytic stability of completely aliphatic novel poly... more The effect of virtual crosslinking on the hydrolytic stability of completely aliphatic novel poly(urethane ureas), HFL9-PU1 (hard-segment content 57.5%) and HFL13-PU2 (hard-segment content 67.9%) based on 4,4'-methylene bis(cyclohexyl isocyanate) (H(12)MDI)-hydroxy-terminated polybutadiene-1,6-hexamethylene diamine, was studied. Fourier transform infrared-attenuated total reflectance and wide-angle X-ray diffraction studies revealed hydrogen-bonding interaction and microphase separation and formation of crystallites by short- and long-range ordering in hard-segment domains. Three-dimensional networks from hydrogen bonding in the present polymers lead to virtually crosslinking and insolubility. These polymers were noncytotoxic to L929 fibroblast cells. The hemolytic potential is below the accepted limit. The studies on in vitro biostability in Ringer's solution, phosphate buffered saline, and papain enzyme revealed no weight loss. The infrared spectral studies revealed changes in the surface, especially on HFL9-PU1 aged in Ringer's solution and phosphate buffered saline, and no changes when aged in papain. The marginal changes noticed in tensile properties were attributed to the changes in degree of hydrogen bonding and associated rearrangement of molecular structure in the bulk. The results revealed that the lesser the crosslinking in virgin polymer, the higher the crosslinking in aged polymer and vice versa. Increased crosslinking during aging provided increased tensile properties in the aged polymer over the virgin polymer and vice versa. For comparison, an aliphatic polyetherurethane urea (HFL16-PU3) was also synthesized using poly(oxy tetra methylene glycol) in addition to the above reactants. Though both HFL9-PU1 and HFL16-PU3 contained the same hard-segment content, the aged sample of the latter showed decreased tensile properties with increased crosslinking during aging in contrast to the former. This was attributed to less microphase separation in the virgin HFL16-PU3 polymer.
Combinatorial Chemistry & High Throughput Screening, 2009
Gradients and arrays have become very useful to the fields of tissue engineering and biomaterials... more Gradients and arrays have become very useful to the fields of tissue engineering and biomaterials. Both gradients and arrays make efficient platforms for screening cell response to biomaterials. Graded biomaterials also have functional applications and make useful substrates for fundamental studies of cell phenomena such as migration. This article will review the use of gradients and arrays in tissue engineering and biomaterials research, with a focus on cellular and biologic responses.
Journal of Materials Science-materials in Medicine, 2010
Electrospun bi-layer tubular hybrid scaffolds composed of poliglecaprone (PGC), polycaprolactone ... more Electrospun bi-layer tubular hybrid scaffolds composed of poliglecaprone (PGC), polycaprolactone (PCL), elastin (E), and gelatin (G) were prepared and thereafter crosslinked by 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC). Scanning electron microscopic (SEM) images revealed a highly porous micro-structure comprising randomly distributed non-woven fibers with the majority of fibers in submicron diameters. The EDC-crosslinking yielded an average crosslinking degree of 40%. Uni-axial tensile test of hydrated scaffolds in both longitudinal and circumferential directions revealed tensile properties, comparable to those of native arteries. The graft (PGC:PCL = 1:3) did not demonstrate significant difference before and after EDC-crosslinking in tensile strength or % strain in either longitudinal or circumferential directions. However, crosslinking increased the Young’s modulus of the graft along the longitudinal direction (from 5.84 to 8.67 MPa). On the contrary, the graft (3:1) demonstrated a significant decrease in maximum strain in both directions. Cyto-assay using human umbilical vein endothelial cells (HUVECs) showed excellent cell viability.
Journal of Non-crystalline Solids, 2003
Materials Chemistry and Physics, 2003
Materials Chemistry and Physics, 2006
Solgel method is useful in the preparation of nanocrystallites-doped gel glasses with relatively... more Solgel method is useful in the preparation of nanocrystallites-doped gel glasses with relatively high particle concentrations, small particle diameter and uniform size distribution [1]. The solgel process allows incorporation of semiconductor nanocrystals along with rare earth ...
Journal of Photochemistry and Photobiology A-chemistry, 2002
Journal of Fluorescence, 2004
Silica glass samples containing CdSe/Eu3+ ions were prepared by sol-gel route. Size distribution ... more Silica glass samples containing CdSe/Eu3+ ions were prepared by sol-gel route. Size distribution and optical band gap of the nanoparticles were calculated from absorption spectrum. It is observed that the presence of CdSe nanocrystallites enhances the fluorescence of europium in silica glass. The phonon sideband spectrum associated with the excitation transition 7F0−5D2 is used to analyze the electron–phonon coupling and nonradiative deexcitiation of the rare earth ions in the glass host. The observed fluorescence enhancement is discussed on the basis of phonon assisted energy transfer from electron-hole recombination of the CdSe nanocrystallites to the rare earth ion and multiphonon relaxation.
Journal of Sol-gel Science and Technology, 2005
Silica glasses doped with Dy3+ were prepared by sol–gel method. The FTIR and thermo gravimetric a... more Silica glasses doped with Dy3+ were prepared by sol–gel method. The FTIR and thermo gravimetric analysis (TGA) clearly show complete densification (density = 2.2 gm/cm3) of the gels around 1000∘C. The fluorescence properties of Dy3+ ion are utilized to study the structural changes during the gel to glass transition of the silica xerogels. The fluorescence intensity and full width at half maximum (FWHM) of the emission bands show an increasing tendency with heat treatment. This is attributed to a glassy silica network with an asymmetric environment. The (Y/B) ratio for the Dy3+ ion is found to be less sensitive to site symmetry effects.
Journal of Physics and Chemistry of Solids, 2003
... PI Paulose a , G. Jose a , V. Thomas a , NV Unnikrishnan Corresponding Author Contact Informa... more ... PI Paulose a , G. Jose a , V. Thomas a , NV Unnikrishnan Corresponding Author Contact Information , E-mail The Corresponding Author , a and MKR Warrier b. a School of Pure and Applied Physics, Priyaddarshini Hills PO, Mahatma Gandhi University, Kottayam 686 560, India. ...
Journal of Biomedical Materials Research Part A, 2008
Development of new generation high flex life polyurethane urea (HFL18-PU) with appropriate elasti... more Development of new generation high flex life polyurethane urea (HFL18-PU) with appropriate elastic modulus, biocompatibility, blood compatibility, resistant to calcification, and biodurability for the long-term use as cardiac device is still a challenge. This study reports the development of a fully aliphatic, ether-free physically cross-linked and low elastic modulus (6.841 ± 0.27 MPa) polyurethane urea having in vivo biostability, in vivo biocompatibility and high flex-life (721 ± 30 million cycles) that can satisfy the requirements for the fabrication of tri-leaflet heart valve. © 2008 Wiley Periodicals, Inc. J Biomed Mater Res, 2009
Journal of Biomaterials Applications, 2000
Polymer International, 2000
... Correspondence: Muthu Jayabalan, Sree Chitra Tirunal Institute for Medical Sciences and Techn... more ... Correspondence: Muthu Jayabalan, Sree Chitra Tirunal Institute for Medical Sciences and Technology ... Also we are grateful to Dr P Ramesh, Mr Roy Joseph, Mr Willi Paul and Mrs C Radhakumari for providing analytical help in the evaluation of the polymers. REFERENCES. ...
Biomacromolecules, 2001
The effect of physical cross-linking in candidate cycloaliphatic and hydrophobic poly(urethane ur... more The effect of physical cross-linking in candidate cycloaliphatic and hydrophobic poly(urethane urea) (4,4'-methylenebis(cyclohexylisocyanate), H(12)MDI/hydroxy-terminated polybutadiene, HTPBD/hexamethylenediamine, HDA) and poly(ether urethane urea)s (H(12)MDI/HTPBD-PTMG/HDA) on the in vitro calcification and blood-material interaction was studied. All the candidate poly(urethane urea)s and poly(ether urethane urea)s elicit acceptable hemolytic activity, cytocompatibility, calcification, and blood compatibility in vitro. The studies on blood-material interaction reveal that the present poly(urethane urea)s are superior to polystyrene microtiter plates which were used for the studies on blood-material interaction. The present investigation reveals the influence of physical cross-link density on biological interaction differently with poly(urethane urea) and poly(ether urethane urea)s. The higher the physical cross-link density in the poly(urethane urea)s, the higher the calcification and consumption of WBC in whole blood. On the other hand, the higher the physical cross-link density in the poly(ether urethane urea)s, the lesser the calcification and consumption of WBC in whole blood. However a reverse of the above trend has been observed with the platelet consumption in the poly(urethane urea)s and poly(ether urethane urea)s.
Journal of Biomedical Materials Research, 2001
The effect of virtual crosslinking on the hydrolytic stability of completely aliphatic novel poly... more The effect of virtual crosslinking on the hydrolytic stability of completely aliphatic novel poly(urethane ureas), HFL9-PU1 (hard-segment content 57.5%) and HFL13-PU2 (hard-segment content 67.9%) based on 4,4'-methylene bis(cyclohexyl isocyanate) (H(12)MDI)-hydroxy-terminated polybutadiene-1,6-hexamethylene diamine, was studied. Fourier transform infrared-attenuated total reflectance and wide-angle X-ray diffraction studies revealed hydrogen-bonding interaction and microphase separation and formation of crystallites by short- and long-range ordering in hard-segment domains. Three-dimensional networks from hydrogen bonding in the present polymers lead to virtually crosslinking and insolubility. These polymers were noncytotoxic to L929 fibroblast cells. The hemolytic potential is below the accepted limit. The studies on in vitro biostability in Ringer's solution, phosphate buffered saline, and papain enzyme revealed no weight loss. The infrared spectral studies revealed changes in the surface, especially on HFL9-PU1 aged in Ringer's solution and phosphate buffered saline, and no changes when aged in papain. The marginal changes noticed in tensile properties were attributed to the changes in degree of hydrogen bonding and associated rearrangement of molecular structure in the bulk. The results revealed that the lesser the crosslinking in virgin polymer, the higher the crosslinking in aged polymer and vice versa. Increased crosslinking during aging provided increased tensile properties in the aged polymer over the virgin polymer and vice versa. For comparison, an aliphatic polyetherurethane urea (HFL16-PU3) was also synthesized using poly(oxy tetra methylene glycol) in addition to the above reactants. Though both HFL9-PU1 and HFL16-PU3 contained the same hard-segment content, the aged sample of the latter showed decreased tensile properties with increased crosslinking during aging in contrast to the former. This was attributed to less microphase separation in the virgin HFL16-PU3 polymer.
Combinatorial Chemistry & High Throughput Screening, 2009
Gradients and arrays have become very useful to the fields of tissue engineering and biomaterials... more Gradients and arrays have become very useful to the fields of tissue engineering and biomaterials. Both gradients and arrays make efficient platforms for screening cell response to biomaterials. Graded biomaterials also have functional applications and make useful substrates for fundamental studies of cell phenomena such as migration. This article will review the use of gradients and arrays in tissue engineering and biomaterials research, with a focus on cellular and biologic responses.
Journal of Materials Science-materials in Medicine, 2010
Electrospun bi-layer tubular hybrid scaffolds composed of poliglecaprone (PGC), polycaprolactone ... more Electrospun bi-layer tubular hybrid scaffolds composed of poliglecaprone (PGC), polycaprolactone (PCL), elastin (E), and gelatin (G) were prepared and thereafter crosslinked by 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide hydrochloride (EDC). Scanning electron microscopic (SEM) images revealed a highly porous micro-structure comprising randomly distributed non-woven fibers with the majority of fibers in submicron diameters. The EDC-crosslinking yielded an average crosslinking degree of 40%. Uni-axial tensile test of hydrated scaffolds in both longitudinal and circumferential directions revealed tensile properties, comparable to those of native arteries. The graft (PGC:PCL = 1:3) did not demonstrate significant difference before and after EDC-crosslinking in tensile strength or % strain in either longitudinal or circumferential directions. However, crosslinking increased the Young’s modulus of the graft along the longitudinal direction (from 5.84 to 8.67 MPa). On the contrary, the graft (3:1) demonstrated a significant decrease in maximum strain in both directions. Cyto-assay using human umbilical vein endothelial cells (HUVECs) showed excellent cell viability.