Biomedical subjects

D V Ramesh

Publications and source records attributed to D V Ramesh.

5 recordsLinked to original sources

PubMed1994

Implantable controlled delivery systems for proteins based on collagen--pHEMA hydrogels.

Co-polymeric hydrogels of collagen and poly(hydroxyethyl methacrylate) (pHEMA) were prepared using an ammonium persulphate-sodium metabisulphite redox initiation technique. Fluorescein isothiocyanate (FITC)-labelled bovine serum albumin (BSA) was entrapped into these hydrogels. These gels were modified differently by external cross-linking and made highly porous by incorporation of ethylene glycol. The morphological characteristics of the gels containing FITC-BSA before and after release were studied. The in vitro release of FITC-labelled BSA was studied in phosphate buffer, pH 7.4, at 37 degrees C. The results clearly indicated that collagen-pHEMA hydrogels release FITC-BSA in a zero-order fashion. In the case of uncross-linked hydrogels, the release of FITC-BSA was about 81% within 8 d, compared to 49% for the same period in the case of cross-linked hydrogels. It was also observed that in the case of porous hydrogels the release was very fast (19% in the first hour) and lasted for about 12 h, releasing 76% of FITC-BSA. These results clearly indicated that collagen-pHEMA hydrogels released BSA in a zero-order fashion and that the release rate can be programmed by appropriate modification of the hydrogel matrices.

Animals↗

PubMed1994

Controlled release systems for proteins based on gelatin microspheres.

The preparation and characterization of biodegradable gelatin microspheres for the controlled release of peptides and proteins has been investigated. Bovine serum albumin (BSA) was chosen for incorporation into the gelatin microspheres and the spheres were characterized for the in vitro release of BSA and other properties. BSA was labelled with fluorescein isothiocyanate (FITC) for easy analysis. FITC-BSA was entrapped into the gelatin microspheres using a polymer dispersion technique developed in our earlier studies. The morphological characteristics of microspheres were analysed by optical and scanning electron microscopy (SEM). The optical and SEM photographs of FITC-BSA microspheres showed the solid spherical nature of the spheres. The entrapment efficiency of FITC-BSA was about 62%. The in vitro release pattern of FITC-BSA showed that 51% of the entrapped drug was released during the first day and the release followed approximate zero order kinetics from day 2 onwards. The total release of FITC-BSA lasted for about 8 days. SDS-PAGE analysis revealed that BSA was not degraded by this preparation of microspheres.

Biodegradation, Environmental↗

PubMed1991

In-vitro interaction of mitomycin C and streptomycin A with collagen.

Mitomycin C and streptomycin A were studied for their interaction with soluble collagens from sepia, fish and rat skins using UV absorption spectroscopy at pH 7.4 and 3.0 and equilibrium dialysis. Both the drugs bound to collagen as shown from association constants and could be quantitatively recovered by prolonged dialysis against water showing formation of dissociable bonds between drug and collagen. At pH 7.4, mitomycin C showed greater binding affinity than streptomycin A with collagen from all three species. The reverse trend was seen at pH 3.0. Binding capacity of sepia and fish skin collagens for streptomycin A at pH 3.0 was found to be significantly greater than for mitomycin C.

Animals↗

PubMed1989

In vitro interaction of bleomycin with collagen--equilibrium dialysis technique.

In an earlier communication, we have presented the results of our study on in vitro interaction of bleomycin with collagens of sepia, fish and rat skins using spectrophotometry. Since the spectrophotometric method does not involve physical separation of the bound and unbound portion of the drug, it was considered worthwhile to test the validity of the use of spectral data by equilibrium dialysis. In the present communication, the values of binding between bleomycin and soluble collagens representing vertebrate, lower vertebrate and invertebrate determined independently at pH 7.4 and 3.0 are presented.

Animals↗

PubMed1987

Physico-chemical studies of micelle formation on sepia cartilage collagen solutions in acetate buffer and its interaction with ionic and nonionic micelles. Hydrodynamic and thermodynamic studies.

Sepia cartilage collagen (pepsin-extracted) in acetate buffer (pH = 2.98) forms micelles at a particular concentration below which they do not normally form. The critical micelle concentration (cmc) of the collagen was determined in buffer as well as in SDS, cetyltrimethylammonium bromide (CTAB) and Tween-80 micellar environments at different temperatures. Mutual interaction of collagen micelles with the ionic and nonionic micelles through the formation of the mixed micelle concept has also been found. The cmc of collagen decreased in the presence of SDS and Tween-80 micelles whereas it increased in the presence of CTAB micelles. This clearly suggests that the micelle formation of collagen is facilitated by the presence of SDS and Tween-80 and hindered by CTAB micelles. The various thermodynamic parameters were estimated from viscosity measurements and the transfer of collagen into the micelles of various surfactants and the reverse phenomenon was analyzed. This analysis has also been modelled conceptually as a different phase and the results have supported the above phenomenon. Our thermodynamic results are also able to predict the exact denaturation temperature as well as the structural order of water in the collagen in various environments. The hydrated volumes, Vh, of collagen in the above environments and intrinsic viscosity were also calculated. The low intrinsic viscosity, [eta], of collagen in an SDS environment compared to buffer and other surfactant environments suggested more workable systems in cosmetic and dermatological skin care preparations. The one and two-hydrogen-bonded models of this collagen in various environments have been analyzed. The calculated thermodynamic parameters varied with the concentration of collagen. The change of thermodynamic parameters from coil-coil to random-coil conformation upon denaturation of collagen were calculated from the amount of proline and hydroxyproline residues and compared with viscometric results. Thermodynamic results suggest that the stability of the collagen in the additive environments is in the following order: SDS greater than Tween-80 greater than buffer greater than CTAB.

Acetates↗