Abstract
New types of biodegradable and pH sensitive polyurethanes containing azo derivatives of 5-aminosalicylic acid (5-ASA) were synthesized by condensation of hexamethylene diisocyanate (HDI) with 4, 4-dihydroxy azobenzene-3, 3-dicarboxylic acid (AZO I) or 4, 4-dihydroxy 3-formyl azobenzene-3-carboxylic acid (AZO II). They contained both hydrolysable urethane bonds and enzymatically degradable azo-aromatic links. Degradation of polyurethanes (PU-AZO I and PU-AZO II) in phosphate buffer solutions was pH dependant. In basic conditions AZO I or AZO II was rapidly released over 48h. Incubation of PU-AZO I and PU-AZO II with rat cecal contents at 37°C gradually released 5-ASA, and the amount of drug released was 85% and 78% in 48h respectively. These polyurethane derivatives are being investigated for colon-specific drug delivery systems for treating inflammatory bowel disease based on the pH-dependant degradation of the polymer.
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