Extrudable salicylic acid-based poly(anhydride-esters) for injectable drug releasing applications

Injectable biomaterials have attracted more and more interest owing to their advantages over traditional open surgeries: minimal invasive procedure and ease of handling. Commonly used synthetic injectable polymers exhibited low drug loading and poor biodegradability. In this work, we describe a novel series of degradable copolymers comprising salicylic acid–based poly(anhydride-esters) and poly(ethylene glycol) subunits suitable for injectable drug releasing applications. By tuning the rheology properties, these salicylic acid–based poly(anhydride-esters) and poly(ethylene glycol) copolymers may function as injectable drug delivery vehicles that deliver salicylic acid at the injury site. These copolymers were designed to have glass transition temperatures (T _g ) below 0ºC, resulting in extrudable polymers that behave like viscous fluids at room temperature. Salicylic acid–based poly(anhydride-esters) and poly(ethylene glycol) copolymers of different ratios (2:1, 1:1, and 1:2 salicylic acid–based poly(anhydride-esters) and poly(ethylene glycol)) were synthesized and characterized by nuclear magnetic resonance and Fourier-transform infrared spectroscopies. Their shear viscosities were determined both at room and physiological temperatures. The in vitro drug release profiles, cytotoxicity, and anti-inflammatory activities were assessed. The shear viscosities were found to compare favorably with current injectable barrier materials on the market.