Molecularly Imprinted Artificial Biointerface for an Enzyme-Free Glucose Transistor

A platform based on a highly selective and sensitive detection device functionalized with a well-designed artificial biointerface is required for versatile biosensors. We develop a molecularly imprinted polymer (MIP)-coated gate field-effect transistor (FET) biosensor for low-concentration glucose detection in biological fluid samples such as tears in an enzyme-free manner. The MIP includes glucose templates (GluMIP), in which glucose binds to vinylphenylboronic acid in the copolymerized membrane, resulting in the change in the density of molecular charges of the phenylboronic acid (PBA)/glucose complex. The FET biosensor can detect small biomolecules as long as biomolecular recognition events cause intrinsic changes in the density of molecular charges. As a result, the changes in the output voltage detected using the GluMIP-based FET sensor are fitted to the Langmuir adsorption isotherm equation at various concentrations of sugars, showing the low detection limit of 3 μM and the high sensitivity of 115 mV/decade from 100 μM to 4 mM glucose. On the basis of the equation, the stability constant ( K_a) of PBA with glucose is calculated and found to markedly increase to K_a = 1192 M^-1, which is higher by a factor of a few hundreds than K_a = 4.6 M^-1 obtained by nonelectrical detection methods. Moreover, the GluMIP-coated gate FET sensor shows an approximately 200-fold higher selectivity for glucose than for fructose. This is because glucose binds to PBA more selectively than fructose in the templates, resulting in the generation of negative charges. The electrical properties of the MIP-coated electrode are also evaluated by measuring capacitance. Our work suggests a new strategy of designing a platform based on the MIP-coated gate FET biosensor, which is suitable for a highly selective, sensitive, enzyme-free biosensing system.