Use of Surfactants in Polylactic Acid Protein Microspheres

Abstract

This paper describes the effect on the in vitro release profile of poly(D,L-lactic) acid (DL-PLA), and poly(D,L-lactic-co-glycolic) acid (D,L-PLGA), microspheres containing BSA as a model protein prepared by the double emulsion technique, due to the addition of surfactant agents in the first emulsion (W/O) made using two type of homogenizer. In the first stage D,L-PLA microspheres were prepared with a mixture of Span-40® and Tween-80® to get HLB 6 and 7, W/O ratio in the first emulsion 1:3 and two types of homogenizers (High pressure homogenizer and Sonicator) against microspheres without surfactants. The microspheres made with high pressure homogenizer presented less BSA trapping efficiency and higher burst effect than those made with sonicator which showed a very slow release rate. In the second stage D,L-PLA and D,L-PLGA microspheres with and without surfactant agents and using sonicator were compared. The BSA release from D,L-PLGA microspheres was continuous, but batches with HLB 6 and without surfactant presented a initial release of 55% of the incorporated BSA while batch with HLB 7 showed less burst effect and slower release rate. The D,L-PLA microspheres released a percentage of incorporated drug at the beginning of the in vitro assay and then stopped.