Development of a portable MIP-based electrochemical sensor for detection of SARS-CoV-2 antigen

Abstract

The current COVID-19 pandemic caused by SARS-CoV-2 coronavirus is expanding around the globe. Hence, accurate and cheap portable sensors are crucially important for the clinical diagnosis of COVID-19. Molecularly imprinted polymers (MIPs) as robust synthetic molecular recognition materials with antibody-like ability to bind and discriminate between molecules can perfectly serve in building selective elements in such sensors. Herein, we report for the first time on the development of a MIP-based electrochemical sensor for detection of SARS-CoV-2 nucleoprotein (ncovNP). A key element of the sensor is a disposable sensor chip - thin film electrode - interfaced with a MIP-endowed selectivity for ncovNP and connected with a portable potentiostat. The resulting ncovNP sensor showed a linear response to ncovNP in the lysis buffer up to 111 fM with a detection and quantification limit of 15 fM and 50 fM, respectively. Notably, the sensor was capable of signaling ncovNP presence in nasopharyngeal swab samples of COVID-19 positive patients. The presented strategy unlocks a new route for the development of rapid COVID-19 diagnostic tools.

Keywords: COVID-19 antigen test; Electrochemical sensor; Molecularly imprinted polymer; SARS-CoV-2 nucleoprotein.

Graphical abstract

Fig. 1

COVID-19 diagnostics principle by nconNP sensor analyzing the samples prepared from nasopharyngeal swab specimens of patients.

Fig. 2

Cyclic voltammograms recorded in 1 M KCl solution containing a 4 mM redox probe K₃[Fe(CN)₆]/K₄[Fe(CN)₆] on bare Au (1), and after the subsequent fabrication steps of ncovNP-MIP: modification by 4-ATP (2), DTSSP (3), and ncovNP (4), electrodeposition of PmPD (5) and treatment in 2-ME and acetic acid (6) (see section 2.3 for details).

Fig. 3

(a) Calibration plot of ncovNP sensor obtained at the low concentration range of ncovNP (2–111 fM) in LB. The inset shows typical DPV curves used to construct the calibration plot. (b) Selectivity test of ncovNP sensor showing its responses against the different proteins (S1, E2 HCV, BSA, CD48 and ncovNP) applied at concentrations (0.04, 0.07, 0.09, and 0.11 pM) in LB.

Fig. 4

(a) The calibration plots of ncovNP sensors obtained against COVID-19 negative samples in UTM, 20-fold diluted with LB and spiked with 22.2, 44.4, 66.6, 111, 222, 333 fM of ncovNP. (b) Cross-selectivity test of ncovNP sensor against S1, and mixture of ncovNP and S1 protein in COVID-19 negative sample in UTM 20-fold diluted with LB. The concentrations of ncovNP and S1 were selected in such a way to simulate their concentration ratio taking place in SARS-CoV-19 virus (Bar-On et al., 2020).

Fig. 5

The calibration plot (solid line) of ncovNP sensor obtained by linear regression of the averaged data in Fig. 4a. The blue rectangles represent data points corresponding I_n measured by ncovNP sensor against COVID-19 positive samples in UTM 20-fold diluted with LB. The error bars represent SDs (Miller and Miller, 2005). (For interpretation of the references to colour in this figure legend, the reader is referred to the Web version of this article.)