Glucose affinity measurement by surface plasmon resonance with borate polymer binding

A novel surface plasmon resonance (SPR) sensor bound to the borate polymer PAA-ran-PAAPBA through a layer-by-layer method was proposed for the determination of glucose concentration. In contrast to the enzyme electrode sensor, the use of optical refractive index sensing to detect glucose concentration eliminates the measurement drift caused by bioelectricity when the sensor is implanted into subcutaneous tissue; in addition, a borate polymer was used to replace the glucose oxidase (GOD) enzyme and it does not consume the glucose molecule during measurement through the affinity reaction between the polymer and glucose. In this study, the layer-by-layer self-assembly method was used to immobilize the borate polymer on the surface of the SPR sensor. The effects of the number of layers are discussed in the manuscript, and the regenerability, reproducibility, and stability of the SPR sensor were evaluated. Almost all of the studies are performed under specific alkaline conditions (usually close to or higher than the pKa of PBA). And for the future application in vivo, we further investigated glucose detection at physiological conditions. The measurement resolution of the sensor bound to 12 polymer layers at physiological conditions was 1 mg/dL, and the R-squared value of the glucose concentration-ΔRU fitting curve within 1-1000 mg/dL was as high as 0.998, which indicates that this measurement may form the foundation of an implantable device for the continuous measurement of glucose concentration.