Doctoral Researcher
email [email protected]


Current Research Interests

My work explores biomolecule-enabled, controllable self-assembly of nanocomponents and the purposeful harnessing of biofunctionality on the nano scale. Specific investigations include:

  1. Interfacing redox proteins and nanoelectronic platforms, including highly ordered carbon nanotube arrays and gold nanowire arrays, and translating the electrochemical 'signature' of the proteins into an informative biosignal that can serve as a biosensing system.
  2. Engineering a self-assembling molecular link composed primarily of DNA oligonucleotides to enable the programmable and reversible self-assembly of redox enzymes to desired locations on the nanoelectronic platform.
  3. Exploiting this controllable self-assembling process to construct highly-multiplexed, renewable bio-nanoelectronic devices.
  4. Increasing linker conductivity by DNA metallization to improve the performance of bio-nanoelectronic devices.



  • Ph.D candidate in Engineering (08/2002 - ), Brown University
  • M.S. in Engineering, Brown University (08/2004)
  • B.S. in Biomedical Engineering, concentration in Computer Science (09/1998 - 05/2002), Johns Hopkins University


Publications and Invited Talks

  • Withey, G.D., Kim, J.H., Xu, J.M., 2007. Wiring efficiency of a metallizable DNA linker for site-addressable nanobioelectronic assembly. In press, Nanotechnology, Special Issue: Design & Function of Molecular & Biological Devices.
  • Withey, G.D., Kim, J.H., Xu, J.M., 2006. DNA-programmable multiplexing for scalable, renewable redox protein bio-nanoelectronics. In review, Biosensors and Bioelectronics.
  • Withey, G.D., Lazareck, A.D., Tzolov, M.B., Yin, A., Aich, P., Yeh, J.I., Xu, J.M., 2006. Ultra-high redox enzyme signal transduction using highly ordered carbon nanotube array electrodes. Biosensors and Bioelectronics,211560-1565.
  • Taft, B.R., Lazareck, A.D., Withey, G.D., Yin, A., Xu, J.M., Kelley, S.O., 2004. Site-specific assembly of DNA and appended cargo on arrayed carbon nanotubes. Jour. Amer. Chem. Soc. 126, 12750-12751.
  • DNA-programmed assembly of a scalable, renewable, multiplexed redox protein-CNT biosensorNano and Giga Challenges in Electronics and Photonics Symposium, Phoenix, AZ **Talk given NSF Award
  • A highly ordered CNT array platform for the DNA-programmed assembly of a redox protein-powered biosensor, Biosciences Global Technology Seminar, General Electric Global Research Center, Niskayuna, NY


Professional Record

  • Intern, General Electric Global Research Center:
    • Visible Human Project (05/2002 - 08/2002): Developing and testing medical registration and segmentation algorithms
    • Information Security Program (05/2001 - 08/2001): Developed a web-based application to evaluate and compare efficacy and cost-efficiency of potential security mechanisms.
    • e-Engineering Program (05/2000 - 08/2000): Web design
  • Research Assistant, Johns Hopkins Medical Institute (1998-1999):
    • Performed benchwork for genetics research involving cell motility deficiencies in drosophila melanogaster.
    • Research won the 2001 David Israel Macht Award and the 2001 Harold Weintraub Award.


More information regarding current projects

Site-addressable assembly of multiple enzymes to specific regions of a CNT array electrode. (a) The cross-linking of enzyme-ssDNA conjugates using the heterobifunctional crosslinker SIAB. An NHS ester reacts with an amine group on the enzyme while the iodoacetyl functional group reacts with a thiolated DNA oligo. (b) Parallel hybridization of five different enzymes to distinct regions of a CNT array electrode modified with differing ssDNA “addresses” (not to scale). The CNTs are exposed from the aluminum oxide template on both sides. The top side is biofunctionalized while electrical contacts are made to the bottom side by gold evaporation. Electrocatalytic currents originating from the enzymes indicate the corresponding substrate concentrations.

Proposed structure and base pairing scheme for metallic DNA (M-DNA). At high pH levels, the imino protons of the thymine and guanine base pairs are replaced by Zn2+. Each base pair therefore coordinates a single Zn2+, resulting in a continuous chain of divalent metal cations along the axis of the duplex. This lends the DNA strand metallic conduction properties, increasing electron transfer versus native B-DNA. Hydrogen bonds are represented by dashed lines. Elements are represented as follows: hydrogen (yellow), oxygen (blue), nitrogen (green), carbon (black), zinc (red).