@article { ISI:000242427200014, title = {Preparation and characterization of urea-formaldehyde-pepsin bioconjugate: a new biocatalyst system}, journal = {Biotechnology Progress}, volume = {22}, number = {6}, year = {2006}, month = {DEC}, pages = {1585-1590}, publisher = {AMER CHEMICAL SOC}, type = {Article}, address = {1155 16TH ST, NW, WASHINGTON, DC 20036 USA}, abstract = {

This study describes the synthesis of urea formaldehyde (UF) microspheres by a dispersion polycondensation polymerization method. These microspheres with proper F/U molar ratio can provide highly reactive groups, capable of further condensation with the amino acid residues of enzyme/proteins. Presence of methylols groups in UF microspheres was confirmed by C-13 NMR study. Pepsin, a proteolytic enzyme, was immobilized on the UF microspheres to form bioconjugate system. As compared to the free enzyme in solution, the pepsin in the bioconjugate system exhibited significantly enhanced pH and temperature stability. The urea-formaldehydepepsin bioconjugate system also exhibited excellent proteolytic activity over eight successive reuse cycles with more than 50\% of initial activity. A highlight of this new biocatalyst is the ease with which separation of this biocatalyst from the reaction medium may be achieved by mild centrifugation.

}, issn = {8756-7938}, doi = {10.1021/bp0602247}, author = {Vinod, V. P. and Shinde, Sudhirkumar and D{\textquoteright}Britto, Virginia and Shukla, P. G. and Rao, Mala} } @article { ISI:000262440400015, title = {Composites of plasma treated poly(etherimide) films with gold nanoparticles and lysine through layer by layer assembly: a {\textquoteleft}{\textquoteleft}friendly-rough{\textquoteright}{\textquoteright} surface for cell adhesion and proliferation for tissue engineering applications}, journal = {Journal of Materials Chemistry}, volume = {19}, number = {4}, year = {2009}, month = {DEC}, pages = {544-550}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

A composite film fabricated by plasma treated poly(etherimide) with subsequent deposition of gold nanoparticles and lysine using layer by layer assembly has been demonstrated to be good for cell attachment and proliferation making it an attractive strategy for tissue engineering applications. As compared to the other methods the decrease in contact angle obtained here does not depend much on the plasma treatment thus affecting the polymer structure minimally. A combination of surface roughness provided by the gold nanoparticles and the presence of amine groups of lysine is hypothesized to be the reason for the features observed.

}, issn = {0959-9428}, doi = {10.1039/b817231e}, author = {D{\textquoteright}Britto, Virginia and Tiwari, S. and Purohit, V. and Wadgaonkar, P. P. and Bhoraskar, S. V. and Bhonde, Ramesh R. and Bhagavatula L. V. Prasad} } @article { ISI:000272797200013, title = {Optical limiting properties of hydrophobic poly(etherimide) membranes embedded with isolated and aggregated gold nanostructures}, journal = {Colloids and Surfaces A-Physicochemical and Engineering Aspects}, volume = {352}, number = {1-3}, year = {2009}, month = {DEC}, pages = {79-83}, publisher = {ELSEVIER SCIENCE BV}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

A simple method to incorporate spherical or aggregated nanostructures of gold into hydrophobic poly(etherimide) membranes is demonstrated and their comparative nonlinear optical properties are investigated. When excited at 532 nm using laser pulses of 7 ns duration, a reduced transmission behaviour in both the cases, viz., polymers embedded with isolated nanoparticles and their aggregates is observed. This fits to a three-photon type nonlinear absorption process and is attributed to excited state absorption occurring in the nanostructures. Interestingly, the nonlinearity is more prominent in the aggregated nanostructures compared to the spherical nanostructures. These materials are potential candidates for optical limiting applications. (C) 2009 Elsevier B.V. All rights reserved.

}, keywords = {gold nanoparticles, Nanoparticle aggregation, Nonlinear optical properties, Optical limiting, Phase transfer, Polymer nanocomposites}, issn = {0927-7757}, doi = {10.1016/j.colsurfa.2009.10.002}, author = {D{\textquoteright}Britto, Virginia and Sandeep, C. S. Suchand and Philip, R. and Bhagavatula L. V. Prasad} } @article { ISI:000274207800015, title = {Cytotoxic and genotoxic assessment of glycolipid-reduced and -capped gold and silver nanoparticles}, journal = {New Journal of Chemistry}, volume = {34}, number = {2}, year = {2010}, month = {NOV}, pages = {294-301}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

A systematic cytotoxic and genotoxic evaluation of glycolipid-conjugated silver and gold nanoparticles is carried out. These glycolipid nanoparticle conjugates are obtained by exploiting the reductive capability of a class of glycolipids called sophorolipids that play the role of capping agent as well. Further, when tested for their cytotoxicity and genotoxicity on HepG2 cells, these nanoparticles are found to be cytocompatible up to 100 mu M metal concentrations. Of the two metallic systems investigated, gold nanoparticles are found to be more cytocompatible than the same concentrations of silver nanoparticles. Similarly, it is also demonstrated that at 100 mu M, silver nanoparticles cause more DNA damage compared to gold nanoparticles of similar concentrations.

}, issn = {1144-0546}, doi = {10.1039/b9nj00277d}, author = {Singh, Sanjay and D{\textquoteright}Britto, Virginia and Prabhune, Asmita and Ramana, C. V. and Dhawan, Alok and Bhagavatula L. V. Prasad} } @article { ISI:000283216900029, title = {Enhancement of anisotropic conductivity, elastic, and dielectric constants in a liquid crystal-gold nanorod system}, journal = {Applied Physics Letters}, volume = {97}, number = {15}, year = {2010}, month = {OCT}, pages = {151913}, publisher = {AMER INST PHYSICS}, address = {CIRCULATION \& FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1, MELVILLE, NY 11747-4501 USA}, abstract = {

We report electrical conductivity (sigma), dielectric constant (epsilon) and the elastic constant measurements in a nematic liquid crystal (LC) doped with small concentrations of gold nanorods. This LC-nanoparticle complex, shows not only orders of magnitude higher sigma, but also stabilizes its anisotropy. The epsilon data suggests an increased ordering in the nematic phase, and an improved antiparallel correlation of the molecules in the isotropic phase. Surprisingly, an anisotropic enhancement of the Frank elasticity is also seen. We suggest a possible electro/magnetomechanical conductivity switch and also provide explanations based on the aspect ratio of the nanoparticles vis-a-vis the LC molecules. (c) 2010 American Institute of Physics. [doi:10.1063/1.3499744]

}, issn = {0003-6951}, doi = {10.1063/1.3499744}, author = {Sridevi, S. and Prasad, S. Krishna and Nair, Geetha G. and D{\textquoteright}Britto, Virginia and Bhagavatula L. V. Prasad} } @article { ISI:000292776300038, title = {Silver nanoparticle studded porous polyethylene scaffolds: bacteria struggle to grow on them while mammalian cells thrive}, journal = {Nanoscale}, volume = {3}, number = {7}, year = {2011}, month = {JUN}, pages = {2957-2963}, publisher = {ROYAL SOC CHEMISTRY}, address = {THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS, ENGLAND}, abstract = {

Silver nanoparticle studded scaffolds were prepared by exploiting the Ag+ ion reducing activity of sophorolipids-a class of {\textquoteleft}glycolipids{\textquoteright} that cap the ensuing nanoparticles as well. To achieve this, the porous polyethylene scaffolds are subjected to N-2+H-2 plasma treatment, in the first step. Subsequently the sophorolipids are covalently attached to the amine groups on the polymer surface through simple amide chemistry to yield sophorolipid grafted polymer scaffolds. These are then exposed to Ag+ ions under appropriate conditions leading to the formation of silver nanoparticles immobilized on the polymer scaffolds. It has been found that while bacteria do not survive on these silver studded scaffolds, CHO-K1 cells thrive on them making them good candidates for tissue engineering and bio-implant applications.

}, issn = {2040-3364}, doi = {10.1039/c1nr10154d}, author = {D{\textquoteright}Britto, Virginia and Kapse, Harsha and Babrekar, Harshada A. and Prabhune, Asmita and Bhoraskar, S. V. and Premnath, V. and Bhagavatula L. V. Prasad} }