Glucose‐sensitive structural color change of cholesteric liquid crystal formed by hydroxypropyl cellulose with phenylboronic acid moieties

Developing durable and simple glucose sensing materials is essential to enable the general population an easy method for testing their glucose levels under different environmental conditions. Hence, materials that enable enzyme-free and intuitive glucose sensing are required. In this study, a system based on an aqueous solution, which enables simple colorimetric glucose detection without the use of enzymes, was developed. The solutions were prepared by dissolving hydroxypropyl cellulose with phenylboronic acid (PBA) moieties (PBA-HPC) in water. The aqueous solutions with a high concentration of PBA-HPC formed a lyotropic cholesteric liquid crystal (ChLC) and exhibited structural color originating from the selective reflection of circularly polarized light. PBA-HPC ChLC aqueous solutions exhibited a color change in response to the increase in the glucose concentration in the solutions. This can be attributed to the change in the side-chain structure of the PBA-HPC caused by the formation of a complex between the PBA moieties and glucose, which induced a change in the cholesteric helical pitch. Thus, the proposed system can be used as a durable and simple enzyme-free glucose sensing material.