Discriminative electrochemical biosensing of wildtype and omicron variant of SARS-CoV-2 nucleocapsid protein with single platform.

Electrochemical biosensors for determining wildtype and omicron variant of the severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) nucleocapsid antigen in nasopharyngeal swab samples were produced by using functionalised graphene oxide and the wildtype and omicron types of SARS-CoV-2 nucleocapsid antibody modified glassy carbon electrodes. The developed biosensors characterised by cyclic voltammetry, scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy were able to detect 0.76 and 0.24 ag/mL of the wildtype and omicron SARS-CoV-2 nucleocapsid antigen protein in linear ranges varied from 1 ag/mL to 100 fg/mL and from 1 ag/mL to 10 fg/mL, respectively. The performance of both biosensors produced was compared in nasopharyngeal swab samples containing the wildtype and omicron variant of the SARS-CoV-2, and it was evaluated whether they could be used interchangeably.

Development and characterisation of cysteine-based gold electrodes for the electrochemical biosensing of the SARS-CoV-2 spike antigen.

This article describes three novel electrochemical biosensing platforms developed to determine the severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) spike antigen protein: glutaraldehyde, SARS-CoV-2 spike antibody and bovine serum albumin; N,N-dicyclohexyl carbodiimide/4-(dimethylamino)pyridine functionalised SARS-CoV-2 spike antibody and bovine serum albumin; and 1-ethyl-3-[3-dimethylaminopropyl]-carbodiimide hydrochloride/N-hydroxysuccinimide functionalised SARS-CoV-2 spike antibody and bovine serum albumin modified cysteine-based gold-flower modified glassy carbon electrodes. Two of the produced biosensors having better signals were used to determine the SARS-CoV-2 spike antigen in spiked-saliva and clinical samples containing gargle and mouthwash liquids and characterised using cyclic voltammetry, scanning electron microscopy, energy dispersive X-ray spectroscopy and X-ray photoelectron spectroscopy. The study provides highly significant information in terms of how coupling reagents ought to be used with linkers consisting of both amine and carboxylic acid terminals (i.e. cysteine). The electrochemical cathodic signals based on antibody-antigen protein interactions at approximately -270 mV were evaluated as a response using square wave voltammetry, and they increased in proportion to the SARS-CoV-2 spike antigen. The limit of detection values were 0.93 and 46.3 ag mL-1 in a linear range from 1 ag mL-1 to 100 pg mL-1 and from 100 ag mL-1 to 10 ng mL-1 and the recovery and relative standard deviation values for spiked-saliva samples were 99.50% and 99.40%, and 3.87% and 0.13% for BSA/S-AB/GluAl/Cys/Au/GCE and BSA/S-AB/f-Cys/Au/GCE, respectively. The results showed that both biosensing platforms could be selectively and accurately used to diagnose COVID-19 in RT-PCR-approved clinical samples.

An Electrochemical Biosensing Platform for the SARS-CoV-2 Spike Antibody Detection Based on the Functionalised SARS-CoV-2 Spike Antigen Modified Electrode.

We developed an electrochemical biosensing platform using gold-clusters, cysteamine, the spike protein of the severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) antigen and bovine serum albumin on a glassy carbon electrode able to determine the SARS-CoV-2 spike antibody. The developed biosensor could detect 9.3 ag/mL of the SARS-CoV-2 spike antibody in synthetic media in 20 min in a linear range from 0.1 fg/mL to 10.0 pg/mL. The developed method demonstrated good selectivity in the presence of spike antigens from other viruses. Clinical samples consisting of gargle and mouthwash liquids were analyzed with both RT-PCR and the developed biosensor system to reveal the sensitivity and specificity of the proposed method. Moreover, the developed method was compared with the lateral flow immunoassay method in terms of sensitivity.

Electrochemical biosensing platform based on hydrogen bonding for detection of the SARS-CoV-2 spike antibody.

Among the deadliest pandemics in history, coronavirus disease 2019 (COVID-19) has wreaked havoc on human lives, economies and public health systems worldwide. To temper its effects, diagnostic methods that are simple, rapid, inexpensive, accurate, selective and sensitive continue to be necessary. In our study, we developed an electrochemical biosensing platform based on gold clusters, mercaptoethanol, the spike protein of severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) antigen and bovine serum albumin-modified glassy carbon electrode able to detect the SARS-CoV-2 spike antibody. Moreover, during the detection of the SARS-CoV-2 spike antibody in spiked-real samples, the anodic signal of the produced biosensor at 0.85 V decreased as the amount of the SARS-CoV-2 spike antibody increased. Meanwhile, the recovery and relative standard deviation values for saliva and oropharyngeal swab samples were 97.73% and 3.35% and 102.43% and 4.63%, respectively. In 35 min, the biosensing platform could detect 0.03 fg/mL of the SARS-CoV-2 spike antibody in synthetic media and spiked-saliva or -oropharyngeal swab samples. The method thus issues a linear response to the SARS-CoV-2 spike antibody from 0.1 fg/mL to 10 pg/mL. The cross-reactivity studies with spike antigens of Middle East respiratory syndrome-coronavirus and influenza A and the antigen of pneumonia confirmed the excellent selectivity of the proposed method. The developed method was compared with the lateral flow immunoassay method in terms of sensitivity and it was found to be approximately 109 times more sensitive. Biosensing mechanism of the platform to the SARS-CoV-2 spike antibody.

Corrigendum to "Electrochemical immunosensor platform based on gold-clusters, cysteamine and glutaraldehyde modified electrode for diagnosing COVID-19" [Microchem. J. 168 (2021) 106445].

[This corrects the article DOI: 10.1016/j.microc.2021.106445.].

Colorimetric and electrochemical detection of SARS-CoV-2 spike antigen with a gold nanoparticle-based biosensor.

Since emerging in China in December 2019, COVID-19 has spread globally, wreaked havoc for public health and economies worldwide and, given the high infectivity and unexpectedly rapid spread of the virus responsible-that is, severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2)-urged the World Health Organization to declare it a pandemic. In response, reducing the virus's adverse effects requires developing methods of early diagnosis that are reliable, are inexpensive and offer rapid response. As demonstrated in this article, the colorimetric and electrochemical detection of SARS-CoV-2 spike antigen with gold nanoparticle-based biosensors may be one such method. In the presence of the SARS-CoV-2 spike antigen, gold nanoparticles aggregated rapidly and irreversibly due to antibody-antigen interaction and consequently changed in colour from red to purple, as easily observable with the naked eye or UV-Vis spectrometry by way of spectral redshifting with a detection limit of 48 ng/mL. Moreover, electrochemical detection was achieved by dropping developed probe solution onto the commercially available and disposable screen-printed gold electrode without requiring any electrode preparation and modification. The method identified 1 pg/mL of the SARS-CoV-2 spike antigen and showed a linear response to the SARS-CoV-2 spike antigen ranging from 1 pg/mL to 10 ng/mL. Both methods were highly specific to detecting the SARS-CoV-2 spike antigen but not other antigens, including influenza A (i.e. H1N1), MERS-CoV and Streptococcus pneumoniae, even at high concentrations.

A rapid, ultrasensitive voltammetric biosensor for determining SARS-CoV-2 spike protein in real samples.

The ongoing coronavirus disease 2019 (COVID-19) pandemic continues to threaten public health systems all around the world. In controlling the viral outbreak, early diagnosis of COVID-19 is pivotal. This article describes a novel method of voltammetrically determining severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) spike protein with a newly designed sensor involving bovine serum albumin, SARS-CoV-2 spike antibody and a functionalised graphene oxide modified glassy carbon electrode (BSA/AB/f-GO/GCE) or screen-printed electrode (BSA/AB/f-GO/SPE). The oxidation reaction based on the antibody-antigen protein interaction was evaluated as a response to SARS-CoV-2 spike protein at -200 mV and 1430 mV with the BSA/AB/f-GO/SPE and BSA/AB/f-GO/GCE, respectively. The developed sensors, BSA/AB/f-GO/SPE and BSA/AB/f-GO/GCE, could detect 1 ag/mL of virus spike protein in synthetic, saliva and oropharyngeal swab samples in 5 min and 35 min, and both sensors demonstrated a dynamic response to the SARS-CoV-2 spike protein between 1 ag/mL and 10 fg/mL. Real-time polymerase chain reaction (RT-PCR), rapid antigen test and the proposed method were applied to saliva samples. When compared to RT-PCR, it was observed that the developed method had a 92.5% specificity and 93.3% sensitivity. Moreover, BSA/AB/f-GO/SPE sensor achieved 91.7% accuracy compared to 66.7% accuracy of rapid antigen test kit in positive samples. In view of these findings, the developed sensor provides great potential for the diagnosing of COVID-19 in real samples.

Electrochemical immunosensor platform based on gold-clusters, cysteamine and glutaraldehyde modified electrode for diagnosing COVID-19.

Amid the global threat caused by the coronavirus disease 2019 (COVID-19) pandemic, developing sufficiently rapid, accurate, sensitive and selective methods of diagnosing both symptomatic and asymptomatic cases is essential to alleviating and controlling the pandemic's effects. This article describes an electrochemical immunoassay platform developed to determine the severe acute respiratory syndrome-coronavirus-2 (SARS-CoV-2) spike antibody by using gold-clusters capped with cysteamine, glutaraldehyde, the spike protein of the SARS-CoV-2 antigen and bovine serum albumin on a glassy carbon electrode. The electrochemical oxidation signal of the antigen-based immunosensor at 0.9 V was used to detect the SARS-CoV-2 spike antibody. When saliva and oropharyngeal swab samples were analysed, the recovery and relative standard deviation values were 96.97%-101.99% and 4.99%-5.74%, respectively. The method's limit of detection relative to the SARS-CoV-2 spike antibody in synthetic media and in saliva or oropharyngeal swab samples was 0.01 ag/mL, while the immunosensor's linear response to the SARS-CoV-2 spike antibody varied from 0.1 to 1000 ag/mL. The cross-reactivity of the Middle East respiratory syndrome-coronavirus spike antigen was evaluated after being immobilised onto the functionalised gold-cluster based sensor, indicated that the good specifity of the produced immunosensor.