Ricinoleic acid-based biopolymers

Polyanhydrides synthesized from pure ricinoleic acid half-esters with malei c and succinic anhydrides possess desired physicochemical and mechanical pr operties for use as drug carriers. Ricinoleic acid maleate or succinate dia cid half-esters were prepared from the reaction of crude ricinoleic acid (8 5% content) with succinic or maleic anhydride. The pure diacid monomers wer e obtained by chromatography purification through silica gel using petroleu m ether/ethyl acetate/acetic acid (80/30/1 v/v/v) mixture as eluent. The pu re diacid monomers (>99%) were polymerized by melt condensation to yield fi lm-forming polymers with molecular weights exceeding 40,000 with a polydisp ersity of 2. Extensive biocompatibility study demonstrated their toxicologi cal inertness and biodegradability. Their rate of elimination from rats in the course of about 4-6 weeks was faster than that found for similar fatty acid-based polyanhydrides previously tested. In vitro studies showed that t hese polymers underwent rapid hydrolytic degradation in 10 days. Methotrexa te release from the polymers was not affected by the initial polymer molecu lar weight in the range of 10,000-35,000. The in vitro drug release correla ted with the degradation of the polymers. The fatty acid ester monomers wer e further degraded to its counterparts, ricinoleic acid and succinic or mal eic acid. (C) 1999 John Wiley & Sons, Inc.