Novel salicylic acid-based chemically crosslinked pH-sensitive hydrogels as potential drug delivery systems.

In this work, salicylic acid (SA), a non-steroidal anti-inflammatory, was chemically incorporated into hydrogel systems to achieve sustained SA release profiles. With its anti-inflammatory properties, sustained release of SA would be relevant for treating diseases such as diabetes and cancer. In this work, SA was chemically incorporated into hydrogel systems via covalent attachment to an itaconate moiety followed by UV-initiated crosslinking using acrylic acid and poly(ethylene glycol) diacrylate. The chemical composition of the hydrogel system was confirmed using FT-IR spectroscopy. The SA-based hydrogels were designed as pH-responsive hydrogels, collapsing at acidic pH (1.2) values and swelling at higher pH (7.4) values for gastrointestinal-specific delivery. The hydrogel systems exhibited a pH-dependent SA release profile: SA release was much slower at pH 1.2 compared to pH 7.4. Under acidic pH conditions, 30wt% SA was released after 24h, whereas 100wt% SA was released in a sustained manner within 24h in pH 7.4 PBS buffer. The pore structure of the gel networks were studied using SEM and exhibit appropriate pore sizes (15-60μm) for physically encapsulating drugs. In addition, rheological studies of the hydrogels proved that these systems are mechanically strong and robust. Mucoadhesive behaviors were confirmed using a Texture Analyzer, the work of adhesion for the hydrogels was around 290 g·mm and the maximum detachment force was around 135g. The SA-based hydrogels demonstrate great potential for oral delivery of bioactives in combination with SA to treat serious diseases such as cancer and diabetes.