Viruses Masquerading as Antibodies in Biosensors: The Development of the Virus BioResistor.

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.

Virus Bioresistor (VBR) for Detection of Bladder Cancer Marker DJ-1 in Urine at 10 pM in One Minute.

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.

Flexible platinum electrodes as electrochemical sensor and immunosensor for Parkinson's disease biomarkers.

In this study, platinum electrodes were fabricated on the bio-based poly(ethylene terephthalate) (Bio-PET) substrates for the development of flexible electrochemical sensors for the detection of Parkinson's disease biomarkers. Dopamine was detected by voltammetric measurements, displaying a 3.5 × 10-5 mol L-1 to 8.0 × 10-4 mol L-1 linear range with a limit of detection of 5.1 × 10-6 mol L-1. Parkinson's disease protein 7 (PARK7/DJ-1) was successfully detected by electrochemical impedance spectroscopy after electrode functionalization with specific anti-PARK7/DJ-1 antibodies. In this case, analytical curves presented a linear behavior from 40 ng mL-1 to 150 ng mL-1 of PARK7/DJ-1 with a limit of detection of 7.5 ng mL-1. Besides, the electrodes did not suffer any change in the electrochemical response after manual tests of mechanical tension. The proposed sensor and immunosensor were applied for the determination of Parkinson's disease biomarkers concentrations found in the human body, being adequate as an alternative method to diagnose this disease.

The significance of calprotectin, CD147, APOA4 and DJ-1 in non-invasive detection of urinary bladder carcinoma.

Aim of the study is to define the diagnostic accuracy of selected urinary protein biomarkers in the non-invasive detection of primary and recurrent urothelial carcinoma of the urinary bladder. The urinary levels of calprotectin, CD147, APOA4 and protein deglycase DJ-1 were examined in 255 individuals, including 60 controls with non-malignant urological disease, 61 patients with a history of urinary bladder cancer with negative cytology and negative cystoscopy and 134 patients with urinary bladder cancer. Urinary concentrations of biomarkers were determined by Enzyme-Linked Immunosorbent Assay (ELISA). During the follow-up of patients with non-muscle invasive bladder cancer (NMIBC), a group of 44 patients with cancer recurrence was compared to the group of 61 patients with a history of NMIBC but with no evidence of disease. Urinary concentrations of the evaluated markers did not reveal any significant difference between these groups. During the primary diagnosis, a group of 90 patients with primary bladder cancer and 60 subjects with benign disease were compared. Urinary levels of CD147 were not significantly higher in patients with tumors. The greatest diagnostic accuracy was observed in APOA4 (sensitivity 55.6, specificity 83.3, AUC 0.75), and lesser in calprotectin (sensitivity 39.4, specificity 87.7, AUC 0.66) and in DJ-1 (sensitivity 61.1, specificity 66.7, AUC 0.64), respectively. Apolipoprotein A4 may be used potentially as a supplemental urinary marker in the diagnosis of primary bladder cancer.