Designing mechanically-stable microcapsules with double-network hydrogel shells for glucose sensing

Abstract

Traditional hydrogel microcapsules often face challenges with mechanical strength, limiting their application. In our research, we develop double-network (DN) hydrogel shells with a water core, using a combination of polyacrylamide and calcium alginate networks created through a triple-emulsion process. These shells provide enhanced mechanical strength, clear visibility, and a specific threshold for substance permeability. This technology is showcased in the creation of a fluorometric glucose sensor. Within the core of these shells, we encase glucose oxidase, while the DN shells themselves contain a pH-reactive fluorescent dye. As glucose permeates the DN shells, it is transformed into gluconic acid by the glucose oxidase, resulting in a lower pH and a decrease in the shell's fluorescence intensity. Moreover, a pH-sensitive dye in the surrounding medium allows for visual monitoring of pH changes. Consequently, glucose concentrations can be measured through both fluorescence and color changes. Remarkably, these DN shells display extraordinary durability, withstanding significant mechanical stress and repeated drying and rehydrating processes without any leakage. Additionally, they effectively protect glucose oxidase from being broken down by large proteins like pancreatin. This DN shell methodology shows great potential, paving the way for a range of sensor capsules that can house various enzymes and catalysts.