Preparation and characterization of alginate-PVA-based semi-IPN: controlled release pH-responsive composites

The objective was to develop naturally derived polymer-based hydrogels with high mechanical strength and a controlled delivery of drug for extended period of time. Here, we report the fabrication of chemically cross-linked polyvinyl alcohol-graft-poly(acrylic acid)/sodium alginate hydrogel as a semi-interpenetrating polymer network (SIPN). For the preparation of SIPN hydrogels, SA and PVA were cross-linked with AA monomer in the presence of co-monomer EGDMA through free-radical polymerization reaction, using APS as an initiator. Loxoprofen sodium was loaded as a model drug. FTIR, XRD, TGA, and DSC were performed for the characterization of copolymer. Surface morphology was studied by SEM. Swelling studies were carried out at low and higher pH to evaluate pH-dependent swelling of formed SIPN hydrogels. FTIR, XRD, TGA, and DSC studies confirmed the formation of a new copolymer. Developed SIPN hydrogels showed maximum swelling, drug loading, and drug release at pH 7.4 while low at pH 1.2. Moreover, formulations with higher AA contents showed maximum swelling at 7.4 pH. High drug loading and higher drug release have been observed at pH 7.4. In vitro release profile of loxoprofen sodium was found dependent on pH, concentration of monomers, and cross-linking agent. Gel% and yield% for the prepared SIPN hydrogels were determined and found that gel% or yield% is directly proportional to the concentration of polymers, i.e., SA and PVA, due to their behavior as macromolecule radicals for monomer. The results from FTIR analysis showed that both SA and PVA react with the acrylic acid monomer during the polymerization process and result into the formation of SIPN. The formation of semi-IPN structure significantly improved the surface morphology of SIPN hydrogels as evident by SEM, which corresponds to their improved swelling ability and mechanical strength. Drug release mechanism from the formed SIPN was explained by kinetic modeling and found that first-order, Higuchi model, and Korsmeyer-Peppas model are the best fit models to explain drug release from hydrogels. Conclusively, prepared hydrogels were highly pH-responsive and showed good mechanical strength and time-dependent drug release. SIPN hydrogels could be a potential carrier network for controlled delivery of loxoprofen sodium for extended period of time.