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Biomedical subjects

R A Mashelkar

Publications and source records attributed to R A Mashelkar.

6 recordsLinked to original sources
PubMed2005

Health innovation networks to help developing countries address neglected diseases.

Gross inequities in disease burden between developed and developing countries are now the subject of intense global attention. Public and private donors have marshaled resources and created organizational structures to accelerate the development of new health products and to procure and distribute drugs and vaccines for the poor. Despite these encouraging efforts directed primarily from and funded by industrialized countries, sufficiency and sustainability remain enormous challenges because of the sheer magnitude of the problem. Here we highlight a complementary and increasingly important means to improve health equity: the growing ability of some developing countries to undertake health innovation.

Biomedical Research↗
PubMed2001

Thermoprecipitation of lysozyme from egg white using copolymers of N-isopropylacrylamide and acidic monomers.

Thermoprecipitation of lysozyme from egg white was demonstrated using copolymers of N-isopropylacrylamide with acrylic acid, methacrylic acid, 2-acryloylamido-2-methylpropane-sulfonic acid and itaconic acid, respectively. Polymers synthesized using molar feed ratio of N-isopropylacrylamide:acidic monomers of 98:2 exhibited lower critical solution temperatures in the range of 33--35 degrees C. These polymers exhibited electrostatic interactions with lysozyme and inhibited its bacteriolytic activity. The concentration of acidic groups required to attain 50% relative inhibition of lysozyme by the polymers, was 10(4)--10(5) times lower than that required for the corresponding monomers. This was attributed to the multimeric nature of polymer-lysozyme binding. More than 90% lysozyme activity was recovered from egg white. Polymers exhibited reusability up to at least 16 cycles with retention of >85% recovery of specific activity from aqueous solution. In contrast, copolymer comprising natural inhibitor of lysozyme i.e. poly (N-isopropylacrylamide-co-O-acryloyl N-acetylglucosamine) lost 50% recovery of specific activity. Thermoprecipitation using these copolymers, which enables very high recovery of lysozyme from egg white, would be advantageous over pH sensitive polymers, which generally exhibit lower recovery.

Acetylglucosamine↗
PubMed1999

Molecularly imprinted adsorbents for positional isomer separation.

2,4-Dihydroxybenzophenone (2,4-DHB) imprinted polymers were synthesized by surface imprinting technique, using allyl alcohol as the functional monomer. The polymers showed a very high selectivity for 2,4-DHB when compared with various positional isomers such as 2-HB, 2,2'-DHB, 4,4'-DHIB and 4,4'-DMB. Solvents were found to affect the selectivity as well as sorption capacity in the case of surface imprinted polymers. The selectivities decreased drastically when the imprint cavity was blocked. This validated the importance of the cavity and the rebinding interactions in governing the selectivity in the case of MIPs. The surface imprinted polymers also showed a high selectivity under non-equilibrium conditions thereby making them suitable adsorbents for industrial separations.

Benzophenones↗
PubMed1999

Preparation of non-porous microspheres with high entrapment efficiency of proteins by a (water-in-oil)-in-oil emulsion technique.

Emulsification-solvent removal methods have been widely used for encapsulating bioactive macromolecules like proteins and polypeptides in biodegradable polymers. We report, a (water-in-oil)-in-oil emulsion technique wherein proteins and polypeptides differing in molecular weight and shape were encapsulated in polymers of current biomedical interest. When an oil was used as the processing medium in combination with a carefully selected mixed solvent system such that a stable (w/o1/o2 emulsion is formed and solvents are removed by a combination of extraction and evaporation, the entrapment efficiency was high and the product nonporous. The entrapment efficiency of globular proteins exceeded 90% while that of fibrous proteins was around 70%. Fracture studies revealed that the polymer matrix was dense. The mechanism of entrapment involved solvent-induced precipitation of the protein as the microspheres were being formed. The principle of the method will find use in preparation of non-porous polymer microparticles with reduced burst effect.

Drug Compounding↗
PubMedDate not supplied

Morphological changes in degrading PLGA and P(DL)LA microspheres: implications for the design of controlled release systems.

The in vitro degradation of microspheres of polymers of lactic and glycolic acids were investigated by monitoring the mass loss from the device, the molecular weight of the polymer and the morphological changes of the particles with time. Two different sequences of morphological changes were found to be operative, depending upon the polymer from which they were made--one, (I) for the high molecular weight P(DL)LA, and the other, (II) for all PLGAs and the low molecular weight P(DL)LA. Microspheres of category I showed clear evidence of heterogeneous degradation, where the initially dense microsphere developed a hollow interior. Microspheres of category II plasticized on hydration due to reduction in the Tg of the polymer below the incubation temperature of 37 degrees C. There was suppression of release of entrapped globular proteins from microspheres that underwent plasticization (category II), while slow and sustained release was seen from those that did not (category I). It is proposed that plasticization renders the matrix of category II microspheres non-porous, which prevents release by pore-diffusion. The mass loss profiles of PLGA were found to be different from those reported in the literature, in that the rates of mass loss after an initial lag time were not as rapid as has been reported. The experimental conditions used, namely the use, or otherwise, of agitation, is suggested as the reason for these differences and the need to draw a correlation between in vitro experimental conditions and in visa behaviour is emphasized.

Biocompatible Materials↗