Reagent-less amperometric glucose biosensor based on a graphite rod electrode layer-by-layer modified with 1,10-phenanthroline-5,6-dione and glucose oxidase

A reagent-less amperometric glucose biosensor operating in not-stirred sample solution was developed. A working electrode of the designed biosensor was based on a graphite rod (GR) electrode, which was modified with 1,10-phenanthroline-5,6-dione (PD) and glucose oxidase (GOx). The PD and the GOx were layer-by-layer adsorbed on the GR electrode surface with subsequent drying followed by chemical cross-linking of the adsorbed GOx with glutaraldehyde (GA). Optimal preparation conditions of the working electrode (GR/PD/ GOx) were achieved with 12.6 mu g and 0.24 mg loading amount of PD and GOx, respectively and 25 min lasting cross-linking of the GOx with GA. A current response to glucose of the GR/PD/GOx electrode was measured at +200 mV potential vs Ag/AgCI reference electrode. Maximum current response was registered when the pH of the buffer solution was 6.0. The registered current response to glucose was linear in the concentration range of 0.1-76 mmol L-1 (R-2=0.9985) and a detection limit was 0.025 mmol L-1. The GR/PD/GOx electrode demonstrated good reproducibility and repeatability with the relative standard deviation of 6.2% and 1.8% (at 4.0 mmol L-1 of glucose), respectively, high anti-interference ability to uric and ascorbic acids. It was highly selective to glucose and demonstrated good accuracy in the analysis of human serum samples.