An amperometric hemoglobin A1c biosensor based on immobilization of fructosyl amino acid oxidase onto zinc oxide nanoparticles–polypyrrole film

Measurement of hemoglobin A1c (HbA1c, glycated hemoglobin) level in blood provides the long-term glucose level in diabetic patients without the influence of short-term fluctuations. The existing methods for HbA1c determination, including biosensors, suffer from insufficient sensitivity, detection limit, response time, and storage stability. These problems were overcome in the current biosensor. A method is described for construction of an amperometric HbA1c biosensor by immobilizing a fructosyl amino acid oxidase (FAO) onto zinc oxide nanoparticles/polypyrrole (ZnONPs/PPy) hybrid film deposited onto gold (Au) electrode and using it as working electrode, Ag/AgCl as reference electrode, and platinum (Pt) as auxiliary electrode. The whole blood samples were hemolyzed and digested by protease before measuring their HbA1c level by the biosensor. The enzyme electrode detected fructosyl valine (FV) as low as 50 μM at a signal-to-noise ratio of 3 within 2 s at +0.27 V versus Ag/AgCl, pH 7.0, and 35 °C with a linear working range of 0.1 to 3.0 mM for FV and sensitivity of 38.42 μA mM−1. The electrode showed only a 30% loss of its initial response over a period of 160 days when stored at 4 °C. The biosensor measured HbA1c in whole blood of apparently healthy individuals and diabetic patients and found it to be in the ranges of 4.0% to 5.6% and 5.7% to 12.0%, respectively.