Controlled release of salicylic acid from poly(D,L-Lactide)

Poly(D,L-Lactide) of high molecular weight (Mv) was prepared by ring-opening bulk polymerization of D,L-Lactide and characterized in terms of Mv, melting point and swelling behavior in buffer solution. Samples of the polymers with low and high Mv (2000 and 22 000 respectively) loaded with various amounts of salicylic acid (SA) were immersed in a buffer solution and the release of SA was recorded. The results obtained showed that swelling of the poly(D,L-Lactide) samples obeyed Fick's law, especially for those with high molecular weight, where biodegradation proceeds slowly. The release of SA seemed to follow a simplified relationship which is linear with time, at least for the early stages of delivery. The extent of linearity is dependent on the content of the acidic SA, which probably accelerates decomposition of the high molecular weight products.