An enzyme–metal–insulator–silicon structured sensor using surface photovoltage technology for potentiometric glucose detection

In this study a potentiometric glucose sensor is constructed with the application of an enzyme–metal–insulator–silicon (EMIS) structure. Glucose biosensing is realized by modifying the metal layer of the sensor with an ultra-thin (<100 nm) film of polypyrrole (PPy)–glucose oxidase (GOD) through an electropolymerization process. The optimum film formation conditions can be provided with 0.1 M pyrrole, 100–200 U/mL GOD, an applied current density of 0.01–0.05 mA/cm2 and an electrical charge of 20–30 mC/cm2. The applicability of the surface photovoltage technology for potential determination is confirmed with an improved sensitivity (106.3 mV/dec) and widened linear range (0.04–10 mM) compared with the traditional two-electrode cell measurement. Good selectivity, stability and lifetime of the potentiometric glucose sensor are also shown. The usage of the ultra-thin PPy–GOD film is advantageous in reducing the response time (from several seconds to less than 80 s) of the sensor, which guarantees its potential in rapid determination of plasma glucose concentration. With ease of fabrication and miniaturization, the photoelectric hybrid glucose sensor can be used in glucose monitoring of extracellular microenvironment.