# IgY antibodies/Cysteamine: simple and effective methodology for electrochemical detection of SARS-CoV-2 S-protein

## TL;DR

This paper presents a new electrochemical method using IgY antibodies and cysteamine to detect SARS-CoV-2 S-protein in saliva with high sensitivity and selectivity.

## Contribution

A label-free, highly sensitive electrochemical immunosensor using IgY antibodies and cysteamine for SARS-CoV-2 S-protein detection is developed.

## Key findings

- The immunosensor detected S-protein in the range of 10 to 1000 ng mL-1 with a limit of detection of 6.2 ng mL-1.
- The method outperformed ELISA in sensitivity and showed selectivity for S-protein over N-protein.
- Saliva sample tests produced results comparable to S-protein standards, indicating practical applicability.

## Abstract

The outbreak of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infections was a serious disease that spread rapidly around the world and led to a state of global health emergency. During the pandemic, millions of deaths were notified as result of the progression of the disease to a serious condition. Research into the development of diagnostic tests was very important for the identification and control of new cases.

In this work a label-free electrochemical platform was developed for sensing of SARS-CoV-2 S-protein.

The S- antibodies (IgY type) from egg yolk were immobilised though stable bonding onto screen-printed gold electrodes surface, which was previously modified with self-assembled monolayers of cysteamine (Cys). The analytical performance of the devices was followed by differential pulse voltammetry after incubation in various concentrations of S-protein.

The electrical response exhibited a linear behaviour from 10 to 1000 ng mL-1 [with limit of detection (LOD) of 6.2 ng mL-1]. Also, we confirmed that our method is more sensitive than an enzyme-linked immuno-sorbent assay (ELISA), which was conducted with the same molecules (antibody and antigen) (500-4000 ng mL-1, with LOD = 235 ng mL-1). The immunosensor was selective for S-protein detection, and no significative changes were registered by differential pulse voltammetry in presence of SARS-CoV-2 N-protein. Tests on saliva samples recorded similar results to S protein standards.

The developed immunosensor showed good performance and selectivity, therefore, it can be an alternative method for coronavirus disease 2019 (Covid-19) detecting in saliva samples.