title: Peptide-nucleic acid-modified ion-sensitive field-effect transistor-based biosensor for direct detection of DNA hybridization.
abstract: Here, we report the development of a peptide-nucleic acid (PNA)-modified ion-sensitive field-effect transistor (IS-FET)-based biosensor that takes advantage of the change in the surface potential upon hybridization of a negatively charged DNA. PNA was immobilized on a silicon nitride gate insulator by an addition reaction between a maleimide group introduced on the gate surface, the succinimide group of N-(6-maleimidocaproyloxy) succinimide, and the thiol group of the terminal cysteine in PNA. The surface was characterized after each step of the reaction by X-ray photoelectron spectroscopy analysis, and the kinetic analysis of the hybridization events was assessed by surface plasmon resonance. In addition, we measured the -potential before and after PNA-DNA hybridization in the presence of counterions to investigate the change in surface charge density at the surface-solution interface within the order of the Debye length. On the basis of the zeta-potential, the surface charge density, DeltaQ, calculated using the Grahame equation was approximately 4.0 x 10(-3) C/m2 and the estimated number of hybridized molecules was at least 1.7 x 10(11)/cm2. The I-V characteristics revealed that the PNA-DNA duplexes induce a positive shift in the threshold voltage, VT, and a decrease in the saturated drain current, ID. These results demonstrate that direct detection of DNA hybridization should be possible using a PNA-modified IS-FET-based biosensor. PNA is particularly advantageous for this system because it enables highly specific and selective binding at low ionic strength.
authors.affiliation: The Institute of Scientific and Industrial Research, Osaka University, 8-1 Mihogaoka, Ibaraki, Osaka 567-0047, Japan. uno32@sanken-osaka-u.ac.jp
authors.forename: Takeshi
authors.initials: T
authors.lastname: Uno
authors.forename: Hitoshi
authors.initials: H
authors.lastname: Tabata
authors.forename: Tomoji
authors.initials: T
authors.lastname: Kawai
mesh_terms: D001483:Base Sequence; D001665:Binding Sites; D015374:Biosensing Techniques / Q000295:instrumentation / Q000379:methods*; D003545:Cysteine / Q000737:chemistry; D004247:DNA / Q000032:analysis* / Q000737:chemistry; D015342:DNA Probes; D007700:Kinetics; D008301:Maleimides / Q000737:chemistry; D015336:Molecular Probe Techniques; D008969:Molecular Sequence Data; D009994:Osmolar Concentration; D020135:Peptide Nucleic Acids / Q000737:chemistry*; D017655:Silicon Compounds / Q000737:chemistry; D013052:Spectrometry, X-Ray Emission; D013388:Succinimides / Q000737:chemistry; D013438:Sulfhydryl Compounds / Q000737:chemistry; D020349:Surface Plasmon Resonance; D013499:Surface Properties; D014173:Transistors, Electronic
chemical_list: D015342:DNA Probes; D008301:Maleimides; D020135:Peptide Nucleic Acids; D017655:Silicon Compounds; D013388:Succinimides; D013438:Sulfhydryl Compounds; D004247:DNA; D003545:Cysteine; C032734:silicon nitride