Bioelectrocatalytic detection of glycated hemoglobin (HbA1c) based on the competitive binding of target and signaling glycoproteins to a boronate-modified surface

We developed an electrochemical glycated hemoglobin (HbA1c) biosensor for diagnosing diabetes in whole human blood based on the competitive binding reaction of glycated proteins. Until now, no studies have reported a simple and accurate electrochemical biosensor for the quantification of HbA1c in whole blood. This is because it is very difficult to correctly distinguish HbA1c from large amounts of hemoglobin and other components in whole blood. To detect glycated hemoglobin, we used electrodes modified with boronic acid, which forms a covalent bond between its diol group and the cis–diol group of the carbohydrate moiety of glycated proteins. For accurate HbA1c biosensing, we first removed blood components (except for hemoglobin) such as glycated proteins and blood glucose as they interfere with the boronate-based HbA1c competition analysis by reacting with the boronate-modified surface via a cis–diol interaction. After hemoglobin separation, target HbA1c and GOx at a predetermined concentration were reacted through a competition onto the boronate-modified electrode, allowing HbA1c to be detected linearly within a range of 4.5–15% of the separated hemoglobin sample (HbA1c/total hemoglobin). This range covers the required clinical reference range of diabetes mellitus. Hence, the proposed method can be used for measuring %HbA1c in whole human blood, and can also be applied to measuring the concentration of various glycated proteins that contain peripheral sugar groups.