PREPARATION OF THERMALLY DENATURED ALBUMIN GEL AND ITS PH-SENSITIVE SWELLING

Heat induced albumin gel was prepared as a candidate for a drug carrie r of a pH sensitive drug delivery system. A given amount of albumin wa s dissolved in phosphate buffer solutions of known pH. Albumin solutio n was heated in a water bath and thermally denatured albumin was obtai ned. Before beating, the absorbance of albumin solution was measured s pectrophotometically at 600 nm. The structure of thermally denatured a lbumin was analyzed by Fourier transform infrared (FTIR). Heat induced albumin gels were swelled to their equilibrium state in aqueous swell ing mediums of given pH. The structure of thermally denatured albumin depends on the pH of albumin solution, i.e. the charge distribution of albumin molecule in solution. The structure of heat induced albumin a ffected the equilibrium swelling ratio and pH sensitivity in swelling. The equilibrium swelling ratio of heat induced albumin increased with the increase of pH of swelling medium on the right side of isoelectri c point of albumin. On the other hand, the swelling ratio decreased as the pH of swelling medium increased, on the left side of isoelectric point. At the isoelectric point, the swelling ratio showed a minimum v alue. Gel, which was made from albumin solution whose pH was adjusted to high value, was found to have high pH sensitivity in swelling. (C) 1998 Elsevier Science B.V. All rights reserved.