Dual-Mode pH-Programmable Enzymatic Hydrogel System for On-Demand Glucose Generation

Abstract

We report a supramolecular enzymatic composite hydrogel system based on starch, chitosan, and Ca²⁺-crosslinked alginate, designed to investigate the coupling between mass transport and enzymatic reaction kinetics in a soft hydrated polymer network. The system integrates amyloglucosidase (AMG) within a polysaccharide matrix stabilized by hydrogen bonding, electrostatic interactions, and ionic coordination, forming a mechanically robust, highly hydrated, and biocatalytically active material. The catalytic response is governed by the pronounced pH dependence of AMG, which exhibits maximal activity under acidic conditions and strong suppression at neutral to mildly alkaline pH. Two complementary control strategies are demonstrated: (i) bulk pH switching, enabling sustained but diffusion-limited enzymatic activation and glucose release from hydrogel microbeads, and (ii) electrochemically induced local pH modulation at a hydrogel-coated electrode interface, providing spatially localized and reversible control over enzymatic activity. Comparison of these two transport regimes reveals that electrochemically generated local pH gradients significantly accelerate switching kinetics relative to bulk pH triggering owing to reduced effective diffusion length scales at the hydrogel–electrode interface. These results demonstrate how supramolecular hydrogel architecture and externally imposed pH gradients jointly regulate enzymatic reaction dynamics in soft hydrated materials.