Point-of-Care Diagnostic Biosensors to Monitor Anti-SARS-CoV-2 Neutralizing IgG/sIgA Antibodies and Antioxidant Activity in Saliva

Abstract

Monitoring biomarkers is a great way to assess daily physical condition, and using saliva instead of blood samples is more advantageous as the process is simple and allows individuals to test themselves. In the present study, we analyzed the titers of neutralizing antibodies, IgG and secretory IgA (sIgA), in response to the SARS-CoV-2 vaccine, in saliva. A total of 19 saliva and serum samples were collected over a 10-month period 3 weeks after the first vaccine, 8 months after the second vaccine, and 1 month after the third vaccine. The ranges of antibody concentrations post-vaccination were: serum IgG: 81–15,000 U/mL, salivary IgG: 3.4–330 U/mL, and salivary IgA: 58–870 ng/mL. A sharp increase in salivary IgG levels was observed after the second vaccination. sIgA levels also showed an increasing trend. A correlation with trends in serum IgG levels was observed, indicating the possibility of using saliva to routinely assess vaccine efficacy. The electrochemical immunosensor assay developed in this study based on the gold-linked electrochemical immunoassay, and the antioxidant activity measurement based on luminol electrochemiluminescence (ECL), can be performed using portable devices, which would prove useful for individual-based diagnosis using saliva samples.

Surface Modification of Screen-Printed Carbon Electrode through Oxygen Plasma to Enhance Biosensor Sensitivity

“…We have investigated the selectivity using the same antibodies and antigens as in the present study. We also investigated real saliva samples [62] and saliva reproduced samples [5] using a biosensor based on the same principle. The biosensor based on the AuNP showed sufficient selectivity.…”

“…In this study, we compared antibody modification by O 2 -plasma treatment and physical adsorption using our novel immunosensor, which is a gold-linked electrochemical immunoassay (GLEIA). This biosensor is based on a sandwich-type immunoassay applied directly on the electrode and detects the antigen concentration through the redox current of gold nanoparticles (AuNPs) modified with a secondary antibody [5,25,[58][59][60][61][62]. Specifically, the AuNPs on the electrode are oxidized at a high potential to produce gold ions, and the concentration of nanoparticles is quantified by measuring the reduction current of gold ions.…”

Why Should Vaccines against Respiratory Diseases Go Mucosal? B Cell Epitope-Based Vaccines against SARS-CoV-2

“…On the other hand, parenteral vaccinations generally cause a greater induction of virus-specific IgG in blood than nasal vaccinations [16,21,22]. Primarily, the s-IgA antibodies serve as neutralizing antibodies (nAbs) to inhibit viral or bacterial binding to the mucosa and, thus, protect it from the entry of the pathogen to the cells [8,23,24]. Furthermore, due to their lack of capacity in activating the classical complement pathway, unlike IgG antibodies, the immune response mediated by s-IgA antibodies at the mucosal site is noninflammatory [25][26][27][28].…”