Electrical quantification of low concentrations of specific protein in complex biological solutions

Abstract

A sensitive immunosensor based on charge detection is developed for proteins. Its aim is to select and quantify low protein concentrations in a complex environment. This highly sensitive sensor is a SGFET (Suspended Gate Field Effect Transistor) whose gate is suspended at 500 nm high above the silicon channel and embedded in silicon nitride. This electrical insulation and the general design of the sensor allow to graft biomolecules and to experiment in liquids and particularly in complex biological solutions. To prove its efficiency, a blood plasma protein is used as an example : the transferrin. Specific antibodies are covalently immobilized under the gate by a new highly reproducible chemical functionalization. SGFET is duplicated in a 3x3 matrix that permits to produce statistical results and to increase reliability. Moreover, our device can detect and quantify a specific protein, here transferrin with 10 to 100 more sensitivity than current clinical tests in a complex solution.