A Low-Cost Handheld Impedimetric Biosensing System for Rapid Diagnostics of SARS-CoV-2 Infections

Abstract

Current laboratory diagnostic approaches for virus detection give reliable results, but they require a lengthy procedure, trained personnel, and expensive equipment and reagents; hence, they are not a suitable choice for home monitoring purposes. This paper addresses this challenge by developing a portable impedimetric biosensing system for the identification of COVID-19 patients. This sensing system has two main parts: a throwaway two-working electrode (2-WE) strip and a novel read-out circuit, specifically designed for simultaneous signal acquisition from both working electrodes. Highly reliable electrochemical signal tracking from multiplex immunosensors provides a potential for flexible and portable multi-biomarker detection. The electrodes' surfaces were functionalized with SARS-CoV-2 Nucleocapsid Antibody enabling the selective detection of Nucleocapsid protein (N-protein) along with self-validation in the clinical nasopharyngeal swab specimens. The proposed programmable highly sensitive impedance read-out system allows for a wide dynamic detection range, which makes the sensor capable of detecting N-protein concentrations between 0.116 and 10,000 pg/mL. This lightweight and economical read-out arrangement is an ideal prospect for being mass-produced, especially during urgent pandemic situations. Also, such an impedimetric sensing platform has the potential to be redesigned for targeting not only other infectious diseases but also other critical disorders.

Keywords: SARS-CoV-2; biosensor; dual electronic read-out system; impedance measurement.

Fig. 1.

An illustration of the step-by-step preparation of immunosensor using bio-ready two-working electrode strips, (a) antibody-immobilization, (b) bovine serum albumin (BSA) blocking, (c) virus surface protein (N-protein) detection (d) sensor connection to the custom-made bi-potentiostat (CM-BiP), and ultimate (e) signal generation and acquisition using CM-BiP system.

Fig. 2.

Illustration of proposed system design. Analog/digital custom-made interface (blue) featuring the potentiostat, attenuator, buffer, impedance converter, range extender and other circuitries for power supply etc. Microcontroller and microprocessor systems (red) are used for the control of the interface system and for graphical user interface (GUI) purposes.

Fig. 3.

Custom designed analog circuitries consisting of (a) excitation signal generator/impedance converter, (b) High pass filter with input from impedance converter, (c) buffer, (d) attenuator, (e) potentiostat, (f) transimpedance amplifier and multiplexer for selection of TIA feedback resistor, (TIA) (g) working electrode Section switch, (h) electrode.

Fig. 4.

Proposed read-out System: (a) whole packaged system, (b) Printed Circuit Board Layout using Altium Designer Software, (c) custom-made PCB, (d) main MCU, (e) RPi board and (f) LCD board.

Fig. 5.

Experimental data analysis for extracting charge transfer resistance ( ) in the range of using 5– 5000 Hz and 1–1400 Hz using the proposed device (D) and Autolab potentiostat Metrohm (M), respectively.

Fig. 6.

Electrochemical characterization of the immunosensor using the (a) CM-BiP potentiostat in this study and (b) the commercialized PGSTAT204. (c) Calibration curve depicting the correlation various protein concentrations in spiked solutions versus the CM-BiP EIS response. (d) Selectivity assessment of the immunosensor when incubated with SARS-CoV-2 Spike protein (S1), and Human Immunoglobulin G (IgG), compared to the N-protein. (e) Stability tests performed from 3 to 5 hours after assay opening at room temperature. (f) Clinical test result. Error bars are associated with three replicates.