title: Surface potential variations on a silicon nanowire transistor in biomolecular modification and detection.
abstract: Using a silicon nanowire field-effect transistor (SiNW-FET) for biomolecule detections, we selected 3-(mercaptopropyl)trimethoxysilane (MPTMS), N-[6-(biotinamido)hexyl]-3(')-(2(')-pyridyldithio) propionamide (biotin-HPDP), and avidin, respectively, as the designated linker, receptor, and target molecules as a study model, where the biotin molecules were modified on the SiNW-FET to act as a receptor for avidin. We applied high-resolution scanning Kelvin probe force microscopy (KPFM) to detect the modified/bound biomolecules by measuring the induced change of the surface potential (ΔΦ(s)) on the SiNW-FET under ambient conditions. After biotin-immobilization and avidin-binding, the ΔΦ(s) on the SiNW-FET characterized by KPFM was demonstrated to correlate to the conductance change inside the SiNW-FET acquired in aqueous solution. The ΔΦ(s) values on the SiNW-FET caused by the same biotin-immobilization and avidin-binding were also measured from drain current versus gate voltage curves (I(d)-V(g)) in both aqueous condition and dried state. For comparison, we also study the ΔΦ(s) values on a Si wafer caused by the same biotin-immobilization and avidin-binding through KPFM and ζ potential measurements. This study has demonstrated that the surface potential measurement on a SiNW-FET by KPFM can be applied as a diagnostic tool that complements the electrical detection with a SiNW-FET sensor. Although the KPFM experiments were carried out under ambient conditions, the measured surface properties of a SiNW-FET are qualitatively valid compared with those obtained by other biosensory techniques performed in liquid environment.
authors.affiliation: Institute of Atomic and Molecular Sciences, Academia Sinica, PO Box 23-166, Taipei 106, Taiwan.
authors.forename: Chia-Chang
authors.initials: CC
authors.lastname: Tsai
authors.forename: Pei-Ling
authors.initials: PL
authors.lastname: Chiang
authors.forename: Chih-Jung
authors.initials: CJ
authors.lastname: Sun
authors.forename: Tsung-Wu
authors.initials: TW
authors.lastname: Lin
authors.forename: Ming-Hsueh
authors.initials: MH
authors.lastname: Tsai
authors.forename: Yun-Chorng
authors.initials: YC
authors.lastname: Chang
authors.forename: Yit-Tsong
authors.initials: YT
authors.lastname: Chen
mesh_terms: D000818:Animals; D001360:Avidin / Q000737:chemistry / Q000378:metabolism*; D015374:Biosensing Techniques / Q000295:instrumentation* / Q000379:methods; D001710:Biotin / Q000737:chemistry / Q000378:metabolism*; D004553:Electric Conductivity; D004867:Equipment Design; D055767:Immobilized Proteins / Q000737:chemistry / Q000378:metabolism; D053770:Nanowires / Q000737:chemistry* / Q000648:ultrastructure; D011485:Protein Binding; D012825:Silicon / Q000737:chemistry*; D013499:Surface Properties; D014173:Transistors, Electronic
chemical_list: D055767:Immobilized Proteins; D001360:Avidin; D001710:Biotin; D012825:Silicon