Detection of Viral Proteins using Human Receptor Functionalized Carbon Nanotubes
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Detection of Viral Proteins using Human Receptor Functionalized Carbon Nanotubes M. Chen1, S.M. Khamis1, S.S. Datta1, Y.-B Zhang2, M. Kanungo2, A.J. Ho2, P. Freimuth2, Daniel van der Lelie2, A.T. Johnson1, J.A. Misewich2, and S.S. Wong2,3 1 University of Pennsylvania, Philadelphia, PA, 19104 2 Brookhaven National Laboratory, Upton, NY, 11973 3 State University of New York at Stony Brook, Stony Brook, NY, 11794 ABSTRACT We present proof-of-concept experiments for developing a highly-sensitive and fastresponse miniaturized single-walled carbon nanotube field-effect transistor (SWNT-FET) biosensor for electrically detecting adenovirus using ligand-receptor-protein specificity. SWNTs are mildly oxidized to form carboxylic groups on the surfaces without compromising the electronic integrity of the nanotubes. Then the human coxsackievirus and adenovirus receptor (CAR) is covalently functionalized onto the nanotube surface via diimide-activated amidation process. Upon exposure of the device to adenovirus protein, Ad12 Knob (Knob), specific binding of Knob to CAR decreases the current that flows through the SWNT-FET device. For control experiment, the CAR-SWNT device is exposed to YieF, which is a virus protein that does not bind specifically to CAR, and no current change is observed. The biological activity of the CAR and Knob proteins that are immobilized on SWNTs has been confirmed by previous fluorescence studies [1]. AFM analysis is done to show height increase of a few nanometers at specific spots where the CAR-Knob complex are covalently linked to the nanotube surface. Therefore, our results show that the human receptor protein CAR does immobilize on SWNT surface while fully retains its biological activity. Moreover, the specific binding of CAR to its complementary adenovirus Knob can be electrically detected using individual SWNT-FET devices. These findings suggest that CAR-functionalized SWNT-FETs can ably serve as biosensors for detection of environmental adenoviruses. INTRODUCTION Semiconducting single walled carbon nanotubes (SWNTs), with all the carbon atoms arranged in a one-dimensional cage structure, are exquisitely sensitive to variations in the surrounding electrostatic environment. Bare SWNTs are found to be sensitive to various gases [2-4], and the responses are significantly enhanced by functionalization of nanotubes with polymers [5] and single-stranded DNA oligomers [6]. The compatibility between the SWNTs and biological systems makes biologically functionalized carbon nanotubes promising nanoscaled biosensors, where the interactions between the functionalized and the targeted molecules provide specific recognition capability [7-9], and the SWNT field effect transistors (FETs) serve as efficient electronic readout components. In nature, an infection from adenovirus is initiated by the formation of high affinity complex between the Knob trimer on the adenovirus and the complementary receptors (CAR) on cell surfaces [10]. The binding between the CAR and the Knob is highly specific. In this
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