Selective Electrochemical Sensing of Glycated Hemoglobin (HbA1c) on Thiophene-3-Boronic Acid Self-Assembled Monolayer Covered Gold Electrodes

We report a novel concept of sensing glycated hemoglobin, HbA(1c), which is now the most important index for a long-term average blood glucose level, by first selectively immobilizing it on the thiophene-3-boronic acid (T3BA) self-assembled monolayer (SAM)-covered gold electrode by a selective chemical reaction with boronic acid. HbA(1c) thus immobilized is then detected by the label-free electrochemical impedance spectroscopic (EIS) measurements with a redox probe, an equimolar mixture of K3Fe(CN)(6) and K4Fe(CN)(6), present. The rate of charge transfer between the electrode and the redox probe is shown to be modulated by the amount of HbA(1c) in the matrix hemoglobin solution due to the blocking effect caused by the binding of HbA(1c) with boronic acid. Both the formation of a well-defined T3BA-SAM on the gold surface and the chemical binding of its boronic acid with HbA(1c), in solution were confirmed by quartz crystal microbalance, atomic force microscopy, and EIS experiments.