Preparation of thermally denatured albumin gel and its pH-sensitive swelling

Abstract

Heat induced albumin gel was prepared as a candidate for a drug carrier of a pH sensitive drug delivery system. A given amount of albumin was dissolved in phosphate buffer solutions of known pH. Albumin solution was heated in a water bath and thermally denatured albumin was obtained. Before heating, the absorbance of albumin solution was measured spectrophotometically at 600 nm. The structure of thermally denatured albumin was analyzed by Fourier transform infrared (FTIR). Heat induced albumin gels were swelled to their equilibrium state in aqueous swelling 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 affected 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 isoelectric 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 value. Gel, which was made from albumin solution whose pH was adjusted to high value, was found to have high pH sensitivity in swelling.