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. 2021 Nov 23;188(12):425.
doi: 10.1007/s00604-021-05092-6.

Sensitive sandwich-type electrochemical SARS-CoV‑2 nucleocapsid protein immunosensor

Ceren Karaman  1 , Bahar Bankoğlu Yola  2 , Onur Karaman  3 , Necip Atar  4 , İlknur Polat  5 , Mehmet Lütfi Yola  6
Affiliations

Sensitive sandwich-type electrochemical SARS-CoV‑2 nucleocapsid protein immunosensor

Ceren Karaman et al. Mikrochim Acta. .

Abstract

A sensitive and fast sandwich-type electrochemical SARS-CoV‑2 (COVID-19) nucleocapsid protein immunosensor was prepared based on bismuth tungstate/bismuth sulfide composite (Bi2WO6/Bi2S3) as electrode platform and graphitic carbon nitride sheet decorated with gold nanoparticles (Au NPs) and tungsten trioxide sphere composite (g-C3N4/Au/WO3) as signal amplification. The electrostatic interactions between capture antibody and Bi2WO6/Bi2S3 led to immobilization of the capture nucleocapsid antibody. The detection antibody was then conjugated to g-C3N4/Au/WO3 via the affinity of amino-gold. After physicochemically characterization via transmission electron microscopy (TEM), scanning electron microscopy (SEM), x-ray diffraction (XRD), and x-ray photoelectron spectroscopy (XPS), cyclic voltammetry (CV), differential pulse voltammetry (DPV), and electrochemical impedance spectroscopy (EIS) analysis were implemented to evaluate the electrochemical performance of the prepared immunosensor. The detection of SARS-CoV-2 nucleocapsid protein (SARS-CoV-2 NP) in a small saliva sample (100.0 µL) took just 30 min and yielded a detection limit (LOD) of 3.00 fg mL-1, making it an effective tool for point-of-care COVID-19 testing.

Keywords: Bi2WO6/Bi2S3; COVID-19; Electrochemical impedance spectroscopy; Electrochemistry; Immunosensor; Voltammetry; g-C3N4/Au/WO3.

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Conflict of interest statement

The authors declare no competing interests.

Figures

Scheme 1
Scheme 1
Schematic illustration of the fabrication procedure of electrochemical SARS-CoV-2 immunosensor
Fig. 1
Fig. 1
SEM images of A Bi2WO6, B Bi2S3, and C Bi2WO6/Bi2S3; D elemental mapping of Bi2WO6/Bi2S3 composite
Fig. 2
Fig. 2
Raman (A) and B UV–Vis spectra of Bi2WO6, Bi2S3, and Bi2WO6/Bi2S3
Fig. 3
Fig. 3
A SEM image of g-C3N4, TEM images of B and C g-C3N4/Au/WO3, D EDX image of g-C3N4/Au/WO3, and E high-resolution TEM image of g-C3N4/Au/WO3
Fig. 4
Fig. 4
A Cyclic voltammograms, B EIS reponses at (a) bare GCE, (b) Bi2WO6/GCE, (c) Bi2S3/GCE, (d) Bi2WO6/Bi2S3/GCE, (e) c-SARS-CoV-2-Ab1/Bi2WO6/Bi2S3/GCE, (f) BSA/c-SARS-CoV-2-Ab1/Bi2WO6/Bi2S3/GCE, (g) SARS-CoV-2 NP/BSA/c-SARS-CoV-2-Ab1/Bi2WO6/Bi2S3/GCE, (h) the final immunosensor including c-SARS-CoV-2-Ab1, SARS-CoV-2 NP, and d-SARS-CoV-2-Ab2 (scan rate of 50 mV s−1) in 1.0 mM [Fe(CN)6]3− containing 0.1 M KCl, and C DPV responses of the proposed immunosensors incubated with 0.2000 pg mL−1 SARS-CoV-2 NP using g-C3N4/WO3/d-SARS-CoV-2-Ab2 (curve b) in presence of 1.0 mM H2O2, g-C3N4/Au/WO3/d-SARS-CoV-2-Ab2 (curve c) in presence of 1.0 mM H2O2 and in absence of target analyte (curve a)
Fig. 5
Fig. 5
Concentration effect (from 0.01 to 1.00 pg mL−1 SARS-CoV-2 NP) on immunosensor signals, Inset: calibration curve for electrochemical SARS-CoV-2 NP immunosensor (potential range is + 0.0/ + 0.4 V; Parameters are frequency of 100 Hz, pulse amplitude of 25 mV, and scan increment of 5 mV)
Fig. 6
Fig. 6
A Immunosensor selective responses against the prepared solutions (n = 6): (i) 10.0 pg mL−1 MERS-CoV NP + 10.0 pg mL−1 SARS-CoV NP + 10.0 pg mL−1 H1N1, (ii) 0.2000 pg mL−1 SARS-CoV‑2 NP + 10.0 pg mL−1 MERS-CoV NP, (iii) 0.2000 pg mL−1 SARS-CoV‑2 NP + 10.0 pg mL−1 SARS-CoV NP, (iv) 0.2000 pg mL−1 SARS-CoV‑2 NP + 10.0 pg mL−1 H1N1; B Stability test of electrochemical SARS-CoV-2 NP immunosensor including 0.2000 pg mL−1 SARS-CoV-2 NP (n = 6) at 25.0 °C
See this image and copyright information in PMC

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