1. Nano-Bio Lab, Nanotechnology Research and Education Center, Department of Bioengineering, University of Texas at Arlington, Arlington, TX 76019
2. Nano-Bio Lab, Nanotechnology Research and Education Center, Department of Electrical Engineering, University of Texas at Arlington, Arlington, TX 76019
3. Department of Biology, University of Texas at Arlington, Arlington, TX 76010
4. Department of Materials Science and Engineering, University of Texas at Arlington, Arlington, TX 76019
5. Mem. ASME Nano-Bio Lab, Nanotechnology Research and Education Center, Department of Electrical Engineering, Department of Bioengineering, Joint Graduate Studies Committee, Biomedical Engineering Program of University of Texas at Arlington and University of Texas Southwestern Medical Center at Dallas, University of Texas at Arlington, Arlington, TX 76019 e-mail: