Degradable biomaterials with elastomeric characteristics and drug-carrier function

The design of drug-carrying elastomers based on poly(phosphoester-urethanes) (PPUs) is presented. Bis(2-hydroxyethyl)phosphite and bis(6-hydroxyhexyl)phosphite were used as the chain extenders and 1,4-butane diisocyanate was the basis of the hard segment. The labile phosphoester linkage in the backbone of the PPU confers biodegradability on the polymer. Using the reactive phosphite side chain in the PPUs, p-aminosalicylic acid and benzocaine were attached pendantly to the polymer with or without a spacer. In vitro release of both drugs was complete in several hours. In contrast, ethambutol incorporated into the backbone of the polymer was released in over 10 days. Preliminary cytotoxicity of the drug-carrier to a macrophage cell line was also assessed.