Determination of free amino group content of serum albumin microcapsules: II. Effect of variations in reaction time and in terephthaloyl chloride concentration

Abstract

Microcapsules were prepared through interfacial cross-linking of human serum albumin (HSA) using terephthaloyl chloride (TC) at a constant pH of 9.8. Variations were performed in reaction time (for a 2.5% w/v TC concentration) and in TC concentration (for a 30 min reaction time). Determination of free amino groups was performed on lyophilized microcapsules by means of a back titration method using trinitrobenzenesulfonic acid (TNBS). When prolonging the reaction time from 2 to 30 min. microcapsule-NH 2 content progressively decreased from 154 to 60 μmol/g dry weight. These results were in good agreement with those of a previous study conducted using Fourier transform infrared spectroscopy. A slight recovery of free-NH 2 was observed after 60 and 120 min. Increasing TC concentration from 1 to 5% (w/v) resulted in a progressive decrease in microcapsule-NH 2 content from 99 to 38 μmol/g.