Development of sandwich electrochemiluminescence immunosensor for COVID-19 diagnosis by SARS-CoV-2 spike protein detection based on Au@BSA-luminol nanocomposites

Abstract

Coronavirus disease (COVID-19) is a new and highly contagious disease posing a threat to global public health and wreaking havoc around the world. It's caused by the Coronavirus that causes severe acute respiratory syndrome (SARS-CoV-2). In the current pandemic situation, rapid and accurate SARS-CoV-2 diagnosis on a large scale is critical for early-stage diagnosis. Early detection and monitoring of viral infections can aid in controlling and preventing infection in large groups of people. Accordingly, we developed a sensitive and high-throughput sandwich electrochemiluminescence immunosensor based on antigen detection for COVID-19 diagnosis (the spike protein of SARS-CoV-2). For the spike protein of SARS-CoV-2, the ECL biosensor had a linear range of 10 ng mL^-1 to 10 µg mL^-1 with a limit of detection of 1.93 ng mL^-1. The sandwich ECL immunosensor could be used in early clinical diagnosis due to its excellent recovery in detecting SARS-CoV-2, rapid analysis (90 min), and ease of use.

Keywords: Au@BSA-luminol; COVID-19; Electrochemiluminescence; SARS-CoV-2; Sandwich immunosensor.

Scheme 1

Schematic illustration of the sandwich ECL immunosensor based on Au@BSA-luminol ECL biosensor for the assay SARS-CoV-2 antigen.

Fig. 1

(A) FESEM image of flower-like Au@BSA; (B) EDS analysis of Au@BSA nanoparticles; (C) FT-IR spectra of Au@BSA.

Fig. 2

(A) The Nyquist plots and; (B) Cyclic voltammograms of different modification steps in the 5 mM K₃Fe(CN)₆-K₄Fe(CN)₆ and 0.1 mol/L KCl system for various electrodes: (a) GCE, (b) GCE/AuNps, (c) GCE/AuNps/MUA-MPA, (d) GCE/AuNps/MUA-MPA/Ab1, (e) GCE/AuNps/MUA-MPA/Ab₁/BSA/SARS-CoV-2 antigen (f) GCE/AuNps/MUA-MPA/Ab₁/BSA /SARS-CoV-2 antigen/Luminol-Au @BSA-Ab_2.

Fig. 3

(A) ECL response of the different concentrations of SARS-CoV-2 antigen (from curve a to curve h 10⁻⁵, 2 $\times$ 10⁻⁶, 10⁻⁶, 2 $\times$ 10⁻⁷, 1.5 $\times$ 10⁻⁷, 10⁻⁷, 10⁻⁸ g mL⁻¹, and without target). Inset shows the linear relationship between ECL intensity and the concentration of SARS-CoV-2 antigen. (B) RGB responses extracted from digital images in different concentrations (10⁻⁵, 2 $\times$ 10⁻⁶, 10⁻⁶, 2 $\times$ 10⁻⁷, 1.5 $\times$ 10⁻⁷, 10⁻⁷, 10⁻⁸ g mL⁻¹).

Fig. 4

(A) The selectivity of the ECL biosensor, (B) The ECL curves of the ECL biosensor for detecting SARS-CoV-2 antigen with various concentrations under three potential scans, (C) the long-term stability of the immunosensor, (D) reproducibility of the sensor using ten identical modified electrodes.

Fig. 5

The ECL signal of the ten clinical samples, using the proposed sandwich ECL immunosensor collected with PMT.