A Glucose Biosensor Based on Phosphorescence Lifetime Sensing and a Thermoresponsive Membrane

The adoption of existing continuous glucose monitors (CGMs) is limited by user burden. Herein, a design for a glucose biosensor with the potential for subcutaneous implantation, without the need for a transcutaneous probe or affixed transmitter, is presented. The design is based on the combination of an enzyme-driven phosphorescence lifetime-based glucose-sensing assay and a thermoresponsive membrane anticipated to reduce biofouling. The metalloporphyrin, Pd meso-tetra(sulfophenyl)-tetrabenzoporphyrin ([PdPh₄ (SO₃ Na)₄ TBP]₃ , HULK) as well as glucose oxidase (GOx) are successfully incorporated into the UV-cured double network (DN) membranes by leveraging electrostatic interactions and covalent conjugation, respectively. The oxygen-sensitive metalloporphyrin is incorporated at different levels within the DN membranes. These HULK-containing membranes retain the desired thermosensitivity, as well as glucose diffusivity and primary optical properties of the metalloporphyrin. After subsequently modifying the membranes with GOx, glucose-sensing experiments reveal that membranes prepared with the lowest GOx level exhibit the expected increase in phosphorescent lifetime for glucose concentrations up to 200 mg dL^-1 . For membranes prepared with relatively higher GOx, oxygen-limited behavior is considered the source of diminished sensitivity at higher glucose levels. This proof-of-concept study demonstrates the promising potential of a biosensor design integrating a specific optical biosensing chemistry into a thermoresponsive hydrogel membrane.