Label-free electrochemical detection of glucose and glycated hemoglobin (HbA1c)

Measuring glucose together with glycated hemoglobin (HbA1c) could provide short-term and long-term information of blood glycemic condition after a single treatment. However, it has been a challenge to quantify glucose and HbA1c from single sample drop and strip of electrodes with suitable sensitivity, selectivity, and efficiency. In this paper, we demonstrated a label free & single sample drop electrochemical detection method of glucose and HbA1c by modifying carbon electrodes. Glucose oxidase and capture antibodies (C-Ab) against HbA1c were immobilized onto the first working electrode (WE1) and the second working electrode (WE2) of dual working screen-printed carbon electrodes (DWSPCEs), respectively. WE2 was modified with Gold Nano Flower. After that, 3-mercaptopropionic acid was coated as a linker. Finally, C-Ab was bonded by the linker. The relationship between gold surface area and concentration of HgAuCl₄ was evaluated to optimize HbA1c incubation time. Linear calibration curves for glucose concentration (0.02-35 mM), HbA1c concentration (0.01 to 1mgml^-1), and HbA1c percentage solution (0-14%) were obtained, with correlation coefficients of 0.99. Sensitivities of the biosensor for glucose and HbA1c were 0.5 μAmm^-2mM^-1 and 0.09 μAmm^-2μg^-1ml, respectively. The biosensor also showed proper stability (>93%, 45days) and selectivity (>92%). The efficiency of the proposed biosensor was also compared with those of commercial kits using whole blood samples of diabetic and normal cases. Results of this study demonstrate that this biosensor can measure both glucose and HbA1c electrochemically using label-free methods to overview glycemic conditions of blood samples using cheap and commercially viable dual carbon electrode-based biosensors.