title: Label-free electronic probing of nucleic acids and proteins at the nanoscale using the nanoneedle biosensor.
abstract: Detection of proteins and nucleic acids is dominantly performed using optical fluorescence based techniques, which are more costly and timely than electrical detection due to the need for expensive and bulky optical equipment and the process of fluorescent tagging. In this paper, we discuss our study of the electrical properties of nucleic acids and proteins at the nanoscale using a nanoelectronic probe we have developed, which we refer to as the Nanoneedle biosensor. The nanoneedle consists of four thin film layers: a conductive layer at the bottom acting as an electrode, an oxide layer on top, and another conductive layer on top of that, with a protective oxide above. The presence of proteins and nucleic acids near the tip results in a decrease in impedance across the sensing electrodes. There are three basic mechanisms behind the electrical response of DNA and protein molecules in solution under an applied alternating electrical field. The first change stems from modulation of the relative permittivity at the interface. The second mechanism is the formation and relaxation of the induced dipole moment. The third mechanism is the tunneling of electrons through the biomolecules. The results presented in this paper can be extended to develop low cost point-of-care diagnostic assays for the clinical setting.
authors.affiliation: Center for Integrated Systems, Department of Electrical Engineering, Stanford University, 855 California Ave., Palo Alto, California 94304, USA ; Stanford Genome Technology Center, 855 California Ave., Palo Alto, California 94304, USA.
authors.forename: Rahim
authors.initials: R
authors.lastname: Esfandyarpour
authors.affiliation: Stanford Genome Technology Center, 855 California Ave., Palo Alto, California 94304, USA.
authors.forename: Mehdi
authors.initials: M
authors.lastname: Javanmard
authors.affiliation: University of California Santa Cruz, Santa Cruz, California 95064, USA.
authors.forename: Zahra
authors.initials: Z
authors.lastname: Koochak
authors.affiliation: Center for Integrated Systems, Department of Electrical Engineering, Stanford University, 855 California Ave., Palo Alto, California 94304, USA.
authors.forename: Hesaam
authors.initials: H
authors.lastname: Esfandyarpour
authors.affiliation: Center for Integrated Systems, Department of Electrical Engineering, Stanford University, 855 California Ave., Palo Alto, California 94304, USA.
authors.forename: James S
authors.initials: JS
authors.lastname: Harris
authors.affiliation: Stanford Genome Technology Center, 855 California Ave., Palo Alto, California 94304, USA.
authors.forename: Ronald W
authors.initials: RW
authors.lastname: Davis