Synthesis, characterization and swelling behavior of pH-sensitive polyvinylalcohol grafted poly(acrylic acid-co-2-acrylamido-2-methylpropane sulfonic acid) hydrogels for protein delivery

Abstract

The aim of the current study was to fabricate a pH-sensitive hydrogels for controlled release of Bovine serum albumin (BSA) protein. In this research work, polyvinylalcohol grafted poly(acrylic acid-co-2-acrylamido-2-methylpropane sulfonic acid) (PVOH-g-poly(AA-co-AMPS)) hydrogels with varying AA/AMPS molar ratio were synthesized through free radical graft copolymerization of partially neutralized acrylic monomers and characterized by Fourier transform infrared spectroscopy, Elemental analysis, X-ray diffraction, and Scanning electron microscopy, thermogravimetric analysis. Then, mechanical proprieties of hydrogels were investigated, and drug release behavior with Bovine serum albumin (BSA) as model drug was studied in vitro. The effect of AA/AMPS molar ratio, pH media on the swelling property of hydrogels was optimized. Results indicated that the strong interaction in the hydrogels resulted in the formation of a more stable copolymer. The high values of the grafting percentage which exceeds 800% confirmed the high performance of the grafting and the successful synthesis. Grafting AMPS onto PVOH/AA improved both thermal stability and mechanical properties of hydrogel. The hydrogel is simultaneous sensitive to pH and ionic strength; the swelling ratio maximizes at pH 6.8 medium and shrinks at pH 1.2, and decreases as the ionic strength increases; the swelling dynamic mechanism was explained well by Fickian diffusion and Schott’s pseudo-second-order models. Different kinetic models were applied, and it has been observed that release profile of BSA best followed the Hixson–Crowell for the release of drug in all release media. However, Zero order and Korsmeyer–peppas models only for pH 1.2 and pH 7.4. The swelling of the hydrogels and release of BSA from the drug loaded hydrogels occurred through non-Fickian diffusion mechanism. It is believed that this hydrogel could be potentially used for localized drug delivery