Search

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) × 1 μm ( l), entrained in an ultrathin (∼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 Δ 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 Δ R VBR induced by HSA binding is as high as 200 Ω, 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.

The label-free detection of human serum albumin (HSA) in aqueous buffer is demonstrated using a simple, monolithic, two-electrode electrochemical biosensor. In this device, both millimeter-scale electrodes are coated with a thin layer of a composite containing M13 virus particles and the electronically conductive polymer poly(3,4-ethylenedioxy thiophene) or PEDOT. These virus particles, engineered to selectively bind HSA, serve as receptors in this biosensor. The resistance component of the electrical impedance, Z re , measured between these two electrodes provides electrical transduction of HSA binding to the virus-PEDOT film. The analysis of sample volumes as small as 50 μL is made possible using a microfluidic cell. Upon exposure to HSA, virus-PEDOT films show a prompt increase in Z re within 5 s and a stable Z re signal within 15 min. HSA concentrations in the range from 100 nM to 5 μM are detectable. Sensor-to-sensor reproducibility of the HSA measurement is characterized by a coefficient-of-variance (COV) ranging from 2% to 8% across this entire concentration range. In addition, virus-PEDOT sensors successfully detected HSA in synthetic urine solutions.