Salicylic acid and PEG-contained polyanhydrides: Synthesis, characterization, and in vitro salicylic acid release

Poly [bi(o-carboxyphenyl)adipate-polyethylene glycol] anhydrides-P(BOCA-PEG)-polymeric drugs were synthesized and characterized by Fourier transformed infrared spectroscopy, NNIR, DSC, gel permeation chromatography etc. Salicylic acid loading efficiency of these polymers ranged from 43.5 % to 71.3 %, which was much higher than that of other polymeric drugs with salicylic acid. The in vitro release of salicylic acid from the polymers was carried out in buffer solutions with different pH values and rat gastrointestinal contents. The results showed the release rate of salicylic acid increased with the increase of PEG content in the polymers and the increase of pH value of degradation buffer solution. The rat cecal contents also greatly promoted the release of salicylic acid. In 0.1M phosphate buffer solution at pH8.0, 37degreesC containing 5% rat cecal contents, P(BOCA-PEG200)(80:20) had 15 % salicylic acid released in 21 hr, indicating its potential use in colon-specific salicylic acid delivery.