Development of a long-life capillary enzyme bioreactor for the determination of blood glucose

A long-life capillary enzyme bioreactor was developed that determines glucose concentrations with high sensitivity and better stability than previous systems. The bioreactor was constructed by immobilizing glucose oxidase (GOx) onto the inner surface of a 0.53 mm i.d. fused-silica capillary that was part of a continuous-flow system. In the presence of oxygen, GOx converts glucose to gluconic acid and hydrogen peroxide (H₂O₂). Hydrogen peroxide detection was accomplished using an amperometric electrochemical detector. The integration of this capillary reactor into a flow-injection (FIA) system offered a larger surface-to-volume ratio, reduced band-broadening effects, and reduced reagent consumption compared to packed column in FIA or other settings. To obtain operational (at ambient temp) and storage (at 4 °C) stability for 20 weeks, the glucose biosensing system was prepared using an optimal GOx concentration (200 mg/mL). This exhibited an FIA peak response of 7 min and a detection limit of 10 μM (S/N = 3) with excellent reproducibility (coefficient of variation, CV < 0.75%). It also had a linear working range from 10¹ to 10⁴ μM. The enzyme activity in this proposed capillary enzyme reactor was well maintained for 20 weeks. Furthermore, 20 serum samples were analyzed using this system, and these correlated favorably (correlation coefficient, r² = 0.935) with results for the same samples obtained using a routine clinical method. The resulting biosensing system exhibited characteristics that make it suitable for in vivo application.