The glycated albumin (GA) is the long-term glycemic control marker for diabetes. While hemoglobin A1c (HbA1c) is widely used among glycated proteins, GA reflects average blood glucose level for shorter period than HbA1c and is more sensitive to changes in glycemic level compared to HbA1c. Currently, GA is mainly measured by enzymatic method using fructosyl amino acid oxidase (FAOx) spectroscopically, which requires pretreatment of GA by proteolytic hydrolysis to release the fructosyl amino acid, the substrate of FAOx. Therefore, a simple and rapid measurement method for GA, which doesn’t require the sample pretreatment, and suitable for point of care testing (POCT) is required. The extended gate field effect transistor (EGFET) detects the change of charge distribution on the surface of extended-gate, which is biorecognition element immobilized electrode connected with the gate of FET, and doesn’t require any redox probe, therefore, the measurement principle is very simple and the sensor is easy to be miniaturized. In this study, we aimed to develop immunosensor for GA measurement based on EGFET to be suitable for POCT. The anti-GA IgG was immobilized on gold electrode (sensing electrode) and was connected to the gate of commercially available metal-oxide-semiconductor field-effect transistor (MOSFET) to work as the extended-gate. The potential change on the sensing electrode by the specific binding event of GA to antibody on the surface of sensing electrode was monitored by measuring the change of drain current (Id) while applying reference voltage (Vref) against Ag/AgCl electrode. As the result, the change of Id signal depending on the GA concentration was successfully observed from 1 to 20 µM within 15 min. The developed sensor was specific to GA since no signal change was observed for non-glycated albumin. Therefore, the simple, rapid and miniaturizable immunosensor for GA without pretreatment have been developed based on EGFET.

Development of a glycated albumin sensor based on the extended-gate field effect transistor

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