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Unformatted text preview: Ultrasensitive, label-free, and real-time immunodetection using silicon field-effect transistors Ansoon Kim, a ! Chil Seong Ah, Han Young Yu, Jong-Heon Yang, In-Bok Baek, Chang-Guen Ahn, Chan Woo Park, and Myung Sim Jun Nano-Bio Electronic Devices Team, Electronics and Telecommunications Research Institute (ETRI), Daejeon 305-700, Korea Sungjae Lee b ! Quantum Photonic Science Research Center and BK21 Program, Division of Advanced Research and Education in Physics, Hanyang University, Seoul 133-791, Korea s Received 13 June 2007; accepted 16 August 2007; published online 4 September 2007 d Ultrasensitive, label-free, and real-time prostate-specific antigen s PSA d sensor was developed using n-type silicon nanowire-based structures configured as field-effect transistors using the conventional top-down semiconductor processes. Specific binding of PSA with antibody of PSA s anti-PSA d immobilized on the Si surface through covalent linkage leads to a conductivity change in response to variations of electric field at the surface. The conductance changes depending on PSA concentrations and p H values in solution according to isoelectric point of PSA provide the evidence of the real-time detection of 1 fg/ml PSA. The authors also explored the sensitivity of PSA immunodetection depending on both Sifield-effect transistors s FET d dimensions and doping concentrations to provide strategy for fabrication of an ultrasensitive Si-FET biosensor. 2007 American Institute of Physics . f DOI: 10.1063/1.2779965 g Nanoelectronic biosensor is a burgeoning research area due to their ultrasensitivity and specificity, as well as simple detection scheme. One promising approach for the direct label-free and electrical detection of biomolecules is to use field-effect transistors s FETs d because the conductance of a nanosized channel changes upon binding of small quantity of charged biomolecules to probe receptors grafted onto the channel surface. Many types of semiconductor nanostruc- tures have been applied for FET-based biosensors to detect biological analytes. 1 9 Among them, the silicon nanostruc- tures are more attractive because of their well known prop- erties and fabricating processes of the silicon. In most of the studies, semiconductor nanostructures were prepared by the bottom-up process, 1 3 , 5 9 which causes several problems in commercialization of biosensors due to the difficulties in po- sitioning of individual nanostructures, integrating sensor ar- rays. On the other hand, the top-down process for fabricat- ing silicon nanostructures provides a solution for manufacturing reliable biosensors because it is compatible with well-established silicon-based complementary metal ox- ide semiconductor technology. Stern et al. have recently re- ported the immunodetection of 100 fM immunoglobulin G and immunoglobulin A using a Si-FET device fabricated by top-down processes....
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