Aminosalicylate‐based biodegradable polymers: Syntheses and in vitro characterization of poly(anhydride‐ester)s and poly(anhydride‐amide)s

Poly(anhydride‐ester)s and poly(anhydride‐amide)s derived from both 4‐ and 5‐aminosalicylate acids (4‐ and 5‐ASA) were synthesized and characterized by physicochemical methods. Thermal and solubility characteristics directly correlated to the polymer backbone composition; polymers based on 5‐ASA had greater solubilities in organic solvents than polymers based on 4‐ASA, and the poly(anhydride‐ester)s thermally decomposed at temperatures nearly 100 °C higher than the corresponding poly(anhydride‐amide)s. The polymers were self‐contained, controlled‐release systems that combine the drug and controlled‐release mechanism into the polymer backbone. The erosion and degradation characteristics of the polymers were measured in physiologically relevant media. All polymer matrices fully degraded in media buffered to pH 7.4, whereas in acidic media (pH 1.2), all polymer matrices maintained greater than 50% mass over a 90‐day time period.