Digital biosensors and method of using same

Abstract

A mearsuring instrument is disclosed having a reversibly selective binding protein immobilized upon the insulated-gate region of a field-effect transistor located on a sensor. With the sensor immersed in solution, the protein binds a select component of the solution to the gate producing an effect on a current flowing through the IGFET. A plurality of such binding protein-IGFET arrangements can be provided on the same sensor, including the same binding proteins having different binding coefficients K.sub.D or an array of proteins with different ligand specificity and/or affinity. Analysis of the IGFET's response to binding by a microprocessor allows, for example, the concentration of the component in solution to be determined. With a plurality of different binding proteins employed, the concentration of different components can be determined. Similarly, with binding proteins employed having different binding coefficients K.sub.D, the output of the sensor can be analyzed in either a digital or analog manner, or some combination of the two. To release the component from the protein, heat can be applied to the sensor through a resistive bank integrated into the sensor chip. Alternatively, the application of a reverse bias to the gate can be used to enhance release.