pH-responsive release of small molecule pharmaceuticals from a reworked adsorbent hydrogel for environmental applications

Hydrogels that are engineered for environmental and biomedical applications possess an overlapping set of material and surface properties. In this work, we have repurposed a poly(acrylic acid-co-vinyl sulfonic acid) (PAcVSA) hydrogel that has been previously used for organic dye removal, for the pH-sensitive release of small molecule pharmaceuticals. The engineered PAcVSA hydrogel displayed highly pH-sensitive swelling behaviour with a percentage swelling of 6000% or more in the pH range of 5-8. The known pharmaceutical sulfadiazine (SDA) and an indigenously developed small molecule pharmaceutical (TBS), displayed pH-responsive cumulative release of 82.1% and 80.6% of SDA and TBS, respectively, at pH 5 over 24 h. The difference in cumulative release percentage of the small molecules from PAcVSA at pH 5 and pH 8 is superior compared to other reported pH-responsive synthetic hydrogels. The kinetic modelling of release from the loaded PAcVSA hydrogels suggests different mechanisms underlying release, with Fickian diffusion for SDA and polymer relaxation for TBS. This work represents the successful cross-use of an adsorbent hydrogel relevant for environmental remediation, towards the distinctive carry and release of small molecule pharmaceuticals.