The Virus BioResistor: Wiring Virus Particles for the Direct, Label-Free Detection of Target Proteins.

The virus bioresistor (VBR) is a chemiresistor that directly transfers information from virus particles to an electrical circuit. Specifically, the VBR enables the label-free detection of a target protein that is recognized and bound by filamentous M13 virus particles, each with dimensions of 6 nm (w) X 1 mu m (1), entrained in an ultrathin (similar to 250 nm) composite virus-polymer resistor. Signal produced by the specific binding of virus to target molecules is monitored using the electrical impedance of the VBR: The VBR presents a complex impedance that is modeled by an equivalent circuit containing just three circuit elements: a solution resistance (R-soln) a channel resistance (R-VBR ), and an interfacial capacitance (C-VBR). The value of R-VBR, measured across 5 orders of magnitude in frequency, is increased by the specific recognition and binding of a target protein to the virus particles in the resistor, producing a signal Delta R-VBR . The VBR concept is demonstrated using a model system in which human serum albumin (HSA, 66 kDa) is detected in a phosphate buffer solution. The VBR cleanly discriminates between a change in the electrical resistance of the buffer, measured by R-soln , and selective binding of HSA to virus particles, measured by R-VBR . The Delta R-VBR induced by HSA binding is as high as 200 Omega, contributing to low sensor-to-sensor coefficients-of-variation (<15%) across the entire calibration curve for HSA from 7.5 nM to 900 nM. The response time for the VBR is 3-30 s.