Diamond electrolyte solution gate FETs for DNA and protein sensors using DNA/RNA aptamers

For DNA and protein detection, we have analyzed DNA/RNA immobilized biosensors based on diamond field effect transistors (FETs), where several types of atomic or molecule termination have been realized on their surfaces. Amine termination and carboxyl termination necessary for biomolecule immobilization can be formed directly on the diamond surfaces resulting in the immobilization of short DNA/RNA within 5 nm from the surface. Owing to the high areal capacitance of a liquid electric double layer capacitor and a solid channel capacitor, the change in the surface charge caused by the hybridization of DNA/RNA and the protein binding to DNA/RNA aptamers can be efficiently detected. The charge of surface termination groups such as NH3+, O-, COO- affects the suppression of nonspecific binding. The detection of biomolecules such as one-base mismatch of DNA and proteins that is unaffected by nonspecific binding can be realized as a result. (C) 2011 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim