Effect of Plasticizers of the Triester Glycerol Type on the Release of Albumin fromBiodegradable Polymer Matrices

Overview

Bovine serum albumin was heterogeneously dispersed in the terpolymer of DL-lactic acid, glycolicacid, and mannitol. The terpolymeric carrier was plasticized by triacetin, tributyrin, or a mixture oftriacetin with tricaprylin.Matrices were prepared by mixing a melt of the carrier with the plasticizerand albumin. Liberation was tested in 1/15 mol.l-1 phosphate buffer pH 7.4 and took place in twostages – the burst and the stage of the continual process. The burst represented 30 % to 90 % ofliberated albumin. The second, continual stage began on day 4 of liberation and within ten daysmaximally 10 % of the total amount of albumin was released. The course of liberation was mostmarkedly influenced by the parameters of the oligoester carrier, its molecular weight, and the degreeof branching. The total extent of albumin liberation was influenced partly by its irreversibleadsorption on the carrier, partly by its polymerization. The extent of adsorption and polymerizationof albumin was increased with the molecular weight of the carrier and decreased with the increasingdegree of its branching. Albumin liberation was positively influenced by the presence of plasticizersin matrices, triacetin being demonstrated as the best one.

Key words:
oligoester matrices – albumin liberation – effect of carriers – effect of triglycerides