Preparation of pH-responsive starch/sodium alginate hybrid hydrogels for smart monitoring applications

Bio-based hydrogels have garnered significant attention in flexible sensing and biomedicine due to their exceptional biocompatibility and biodegradability. However, the developing flexible sensors capable of real-time biochemical monitoring during human activities remains a formidable challenge. In this study, we fabricated a novel pH-responsive poly(acrylic acid)/sodium alginate/starch hydrogels (PAA/SA/SH) with inherent antimicrobial properties through thermal polymerization. The hydrogel was synthesized by incorporating maize starch and sodium alginate with pH-sensitive itaconic acid and acrylic acid, while d-limonene was integrated to impart antimicrobial efficacy. The resulting PAA/SA/SH hydrogels exhibited remarkable pH-dependent swelling behavior, with an equilibrium swelling ratio increasing from 400 % at pH 2 to 9200 % at pH 12. This substantial swelling variation directly influenced the hydrogel's electrical conductivity, which was modulated by changes in volume and water content. Furthermore, the hydrogels demonstrated excellent biodegradability, adhesion, transparency, mechanical properties, stable sensing properties, and potent antimicrobial activity. Given these advantages, the pH-responsive behavior of PAA/SA/SH hydrogels holds significant promise for the development of wearable flexible sensors capable of monitoring pH fluctuations in human body fluids, offering potential applications in personalized healthcare and smart diagnostics.