Glucose sensing electrodes based on a poly(3,4-ethylenedioxythiophene)/Prussian blue bilayer and multi-walled carbon nanotubes

Here we report a new glucose sensing electrode based on a poly(3,4-ethylenedioxythiophene) (PEDOT)/Prussian blue (PB) bilayer and multi-walled carbon nanotubes (CNT). The bilayer was prepared on a flexible screen-printed carbon electrode (SPCE) by sequential electrodeposition. The inner PB layer was electrodeposited first for detecting H2O2 from glucose oxidation; the outer PEDOT layer was electropolymerized on a baked or an unbaked PB film to entrap glucose oxidase (GOD). It was observed that the stability of PB in phosphate buffered saline (pH 7.4) was attained by post-deposition bake at 100 °C and the outer PEDOT layer both. In addition, a baked PB film enhanced the subsequent PEDOT growth and the corresponding GOD entrapment. As a result, the bilayer enzyme electrode showed highly resolved and reproducible signals (R.S.D. = 2.54%) to glucose samples from 100 μM to 1 M during a flow-injection analysis (FIA) at −0.1 V vs. Ag/AgCl. The sensitivity of the linear range (1–10 mM) was 2.67 μA cm−2 mM−1. Moreover, the electrode retained ca. 82% of the original response after 1-month storage in PBS, pH 6.0 at 4 °C and could determine the glucose level in human serum precisely. Besides, it was found that CNT incorporation could further improve the sensitivity and could achieve μM-range glucose detection.