Skip to main content
eScholarship
Open Access Publications from the University of California

Scholarly Works (8 results)

  • Thesis
  • Peer Reviewed
UC Irvine Electronic Theses and Dissertations (2020)

Point of Care (PoC) diagnostics have made healthcare available for a large audience of non-specialists and patients with introduction of miniaturized, simple and user-friendly electronic devices. Electrochemical biosensors have emerged victorious candidates for PoC owing to the ease of transforming a biological interaction to simple electrical signal. This work is dedicated towards exploring a sensor architecture that connects the biological sensing element, virus, to an external circuitry at nanometer scale. Chapter 2 introduces the Virus-bioresistor in detail. It is demonstrated that M13 phage particles can be wired into an electrical circuit by embedding them in an electronically conductive polymer composed of poly(3,4-ethylenedioxythiophene) or PEDOT via electropolymerization. The signals transduced by impedance spectroscopy are recorded as an increased resistance of the virus-PEDOT material in the presence of the target protein and the amplitude of the resistance change allows its concentration in the contacting solution to be measured. This concept is demonstrated on a model system in which a dynamic range of 7.5 nM – 900 nM human serum albumin (HSA, 66kDa) is detected in phosphate buffer solution. The VBR overcomes the challenges of label-free, non-faradaic sensors pertaining to non-specific adsorption and lower sensitivity. Elemental problem of coupling of target binding from ionic conduction is solved as an equivalent circuit description for the data procured, establishes signal independence over solution conductivity. The next segment employs the VBR for detection of bladder cancer biomarker, DJ-1 (20 kDa), which is achieved by engineering the sensing layer that enables successful pico-molar detection of analyte without compromising on the speed and reproducibility of detection. A range of 10 pM – 300 nM DJ-1 protein is detected, which beautifully accommodates the established 100-1000 pM DJ-1 detected in bladder cancer patient’s urine. A possible signal transduction mechanism is uncovered with experiments based on quartz crystal microbalance (QCM) gravimetry. The last section exploits the potentiality of the VBR to be modified in a controlled fashion to enable large biomolecule (antibody) sensing. This is achieved by oxidizing the VBR channel using chronoamperometry. The morphological changes for VBRs have been tracked with microscopy techniques. Overall, this work establishes that VBRs can be associated with speed, specificity and reproducibility with coefficient of variation values <16%. The signal output can be tuned as per convenience to detect biomolecules with molecular weights that fall within an appreciable range of 20 kDa to 150 kDa.

    Cover page: Development and optimization of the Virus-Bioresistor: A potential Point-of-care diagnostic platform
    • Article
    • Peer Reviewed
    UC Irvine Previously Published Works (2020)
    The 2018 Nobel Prize in Chemistry recognized in vitro evolution, including the development by George Smith and Gregory Winter of phage display, a technology for engineering the functional capabilities of antibodies into viruses. Such bacteriophages solve inherent problems with antibodies, including their high cost, thermal lability, and propensity to aggregate. While phage display accelerated the discovery of peptide and protein motifs for recognition and binding to proteins in a variety of applications, the development of biosensors using intact phage particles was largely unexplored in the early 2000s. Virus particles, 16.5 MDa in size and assembled from thousands of proteins, could not simply be substituted for antibodies in any existing biosensor architectures.Incorporating viruses into biosensors required us to answer several questions: What process will allow the incorporation of viruses into a functional bioaffinity layer? How can the binding of a protein disease marker to a virus particle be electrically transduced to produce a signal? Will the variable salt concentration of a bodily fluid interfere with electrical transduction? A completely new biosensor architecture and a new scheme for electrical transduction of the binding of molecules to viruses were required.This Account describes the highlights of a research program launched in 2006 that answered these questions. These efforts culminated in 2018 in the invention of a biosensor specifically designed to interface with virus particles: the Virus BioResistor (VBR). The VBR is a resistor consisting of a conductive polymer matrix in which M13 virus particles are entrained. The electrical impedance of this resistor, measured across 4 orders of magnitude in frequency, simultaneously measures the concentration of a target protein and the ionic conductivity of the medium in which the resistor is immersed. Large signal amplitudes coupled with the inherent simplicity of the VBR sensor design result in high signal-to-noise ratio (S/N > 100) and excellent sensor-to-sensor reproducibility. Using this new device, we have measured the urinary bladder cancer biomarker nucleic acid deglycase (DJ-1) in urine samples. This optimized VBR is characterized by extremely low sensor-to-sensor coefficients of variation in the range of 3-7% across the DJ-1 binding curve down to a limit of quantitation of 30 pM, encompassing 4 orders of magnitude in concentration.
      Creative Commons 'BY' version 4.0 license
      • Article
      • Peer Reviewed
      UC Irvine Previously Published Works (2018)
      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 ( Rsoln), a channel resistance ( RVBR), and an interfacial capacitance ( CVBR). The value of RVBR, 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 RVBR. 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 Rsoln, and selective binding of HSA to virus particles, measured by RVBR. The Δ RVBR 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.
        Creative Commons 'BY' version 4.0 license
        • Article
        • Peer Reviewed
        UC Irvine Previously Published Works (2018)
        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 ( Rsoln), a channel resistance ( RVBR), and an interfacial capacitance ( CVBR). The value of RVBR, 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 RVBR. 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 Rsoln, and selective binding of HSA to virus particles, measured by RVBR. The Δ RVBR 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.
          Cover page: The Virus Bioresistor: Wiring Virus Particles for the Direct, Label-Free Detection of Target Proteins
          • Article
          • Peer Reviewed
          UC Irvine Previously Published Works (2021)
          The Virus BioResistor (VBR) is a biosensor capable of rapid and sensitive detection of small protein disease markers using a simple dip-and-read modality. For example, the bladder cancer-associated protein DJ-1 (22 kDa) can be detected in human urine within 1.0 min with a limit of detection (LOD) of 10 pM. The VBR uses engineered virus particles as receptors to recognize and selectively bind the protein of interest. These virus particles are entrained in a conductive poly(3,4-ethylenedioxythiophene) or PEDOT channel. The electrical impedance of the channel increases when the target protein is bound by the virus particles. But VBRs exhibit a sensitivity that is inversely related to the molecular weight of the protein target. Thus, large proteins, such as IgG antibodies (150 kDa), can be undetectable even at high concentrations. We demonstrate that the electrochemical overoxidation of the VBR's PEDOT channel increases its electrical impedance, conferring enhanced sensitivity for both small and large proteins. Overoxidation makes possible the detection of two antibodies, undetectable at a normal VBR, with a limit of detection of 40 ng/mL (250 pM), and a dynamic range for quantitation extending to 600 ng/mL.
            Creative Commons 'BY' version 4.0 license
            • Article
            • Peer Reviewed
            UC Irvine Previously Published Works (2020)
            DJ-1, a 20.7 kDa protein, is overexpressed in people who have bladder cancer (BC). Its elevated concentration in urine allows it to serve as a marker for BC. However, no biosensor for the detection of DJ-1 has been demonstrated. Here, we describe a virus bioresistor (VBR) capable of detecting DJ-1 in urine at a concentration of 10 pM in 1 min. The VBR consists of a pair of millimeter-scale gold electrodes that measure the electrical impedance of an ultrathin (≈ 150-200 nm), two-layer polymeric channel. The top layer of this channel (90-105 nm in thickness) consists of an electrodeposited virus-PEDOT (PEDOT is poly(3,4-ethylenedioxythiophene)) composite containing embedded M13 virus particles that are engineered to recognize and bind to the target protein of interest, DJ-1. The bottom layer consists of spin-coated PEDOT-PSS (poly(styrenesulfonate)). Together, these two layers constitute a current divider. We demonstrate here that reducing the thickness of the bottom PEDOT-PSS layer increases its resistance and concentrates the resistance drop of the channel in the top virus-PEDOT layer, thereby increasing the sensitivity of the VBR and enabling the detection of DJ-1. Large signal amplitudes coupled with the inherent simplicity of the VBR sensor design result in high signal-to-noise (S/N > 100) and excellent sensor-to-sensor reproducibility characterized by coefficients of variation in the range of 3-7% across the DJ-1 binding curve down to a concentration of 30 pM, near the 10 pM limit of detection (LOD), encompassing four orders of magnitude in concentration.
              Creative Commons 'BY' version 4.0 license
              • Article
              • Peer Reviewed
              UC Irvine Previously Published Works (2020)
              DJ-1, a 20.7 kDa protein, is overexpressed in people who have bladder cancer (BC). Its elevated concentration in urine allows it to serve as a marker for BC. However, no biosensor for the detection of DJ-1 has been demonstrated. Here, we describe a virus bioresistor (VBR) capable of detecting DJ-1 in urine at a concentration of 10 pM in 1 min. The VBR consists of a pair of millimeter-scale gold electrodes that measure the electrical impedance of an ultrathin (≈ 150-200 nm), two-layer polymeric channel. The top layer of this channel (90-105 nm in thickness) consists of an electrodeposited virus-PEDOT (PEDOT is poly(3,4-ethylenedioxythiophene)) composite containing embedded M13 virus particles that are engineered to recognize and bind to the target protein of interest, DJ-1. The bottom layer consists of spin-coated PEDOT-PSS (poly(styrenesulfonate)). Together, these two layers constitute a current divider. We demonstrate here that reducing the thickness of the bottom PEDOT-PSS layer increases its resistance and concentrates the resistance drop of the channel in the top virus-PEDOT layer, thereby increasing the sensitivity of the VBR and enabling the detection of DJ-1. Large signal amplitudes coupled with the inherent simplicity of the VBR sensor design result in high signal-to-noise (S/N > 100) and excellent sensor-to-sensor reproducibility characterized by coefficients of variation in the range of 3-7% across the DJ-1 binding curve down to a concentration of 30 pM, near the 10 pM limit of detection (LOD), encompassing four orders of magnitude in concentration.
                Cover page: Virus Bioresistor (VBR) for Detection of Bladder Cancer Marker DJ‑1 in Urine at 10 pM in One Minute
                • Article
                • Peer Reviewed
                UC Irvine Previously Published Works (2020)
                The author list contained an error: Gregory A. Weiss was not identified as a corresponding author. Both of the corresponding authors, Gregory A. Weiss and Reginald M. Penner, are indicated in this Addition and Correction.
                  Creative Commons 'BY' version 4.0 license
                  Top