Grafted Hydrophilic Polymers As Optical Sensor Substrates

Abstract

A prototype fiber optic oxygen sensor was fabricated by grafting poly(2-hydroxyethylmethacrylate) (PHEMA), containing the oxygen quenchable fluorescent dye, 9,10-diphenylanthracene (9,10-D), to a glass fiber. The PHEMA-glass fiber graft was optimized to maximize stability in hydrolytic environments. The fluorescence of the dye was quenched 20% when the sensor went from an oxygen-free to an oxygen-saturated environment. Transient response times of the sensor were reduced when the PHEMA graft thickness was reduced. Modeling of the transient data gave a diffusion coefficient of oxygen in PHEMA of 2.15 x 10-6 cm2/sec. Glucose oxidase (GOO) was incorporated into PHEMA for the ultimate purpose of converting the fiber optic oxygen sensor into a glucose sensor. Immobilization of glucose oxidase was accomplished through a physical entrapment in the PHEMA matrix. Immobilization parameters such as thickness of the polymer layer, enzyme loading, and polymerization conditions were adjusted to give adequate sensitivity in the desired range of glucose concentrations. Immobilized GOx activity was measured over a wide range of enzyme loadings and glucose concentrations. The feasibility of using PHEMA containing 9,10-D and GOx as a material sensitive to physiological levels of glucose was demonstrated.