Abstract—An atomic force microscope (AFM) and a field effect transistor (FET) were integrated into one functioning novel biosensor to probe single molecular interactions between biomolecules, such as proteins and ligands. The interactions between avidin-biotin complexes were studied using the AFM-FET biosensor. Biotin molecules were attached to the AFM cantilever via flexible polyethylene glycol cross-linkers, and avidin molecules were bound to the palladium gate surface of the FET via the cross-linker molecules, cystamine and glutaraldehyde. The force of the AFM and the FET current between the drain and source was measured as a function of distance when the biotin molecules approached and retracted from the avidin molecules. The measurement data showed that the FET current changed abruptly when binding and unbinding events occurred between the two molecules. This change in the current was generated from the corresponding electric potential, which was related to the magnitude of unbinding force during the binding and unbinding events. The relationship suggests that the AFM-FET biosensor can provide potential voltages generated during the biding and unbinding events. This additional information on molecular interactions at the single molecular level could potentially be used as a quantitative and efficient method for detecting single molecular interactions. The novel AFM-FET biosensor is potentially advantageous over current drug screening methods based on microfluidics, due to the AFM-FET ability to record single interactions more quickly and accurately.

Index Terms—AFM, Biosensor, FET, Molecular interactions

B. I. Kim, J. O. Holmes, and M. S. Ryu are with Boise State University, 1910 University Drive, Boise, ID 83725-1570 (Tel.: (208)-426-3659; fax: (208)-426-4330; e-mail: ByungKim@boisestate.edu).
P. Deschateletes is with Potentia Pharmaceutical Inc.

Cite: Byung I. Kim, Joseph O. Holmes, Moon S. Ryu, and P. Deschateletes, "An AFM-FET Biosensor for Proteomic Screening," International Journal of Bioscience, Biochemistry and Bioinformatics vol. 2, no. 3, pp. 168-173, 2012.