# Highly Sensitive Detection of Anti-SARS-CoV-2 Antibodies in Human Serum Using Bloch Surface Wave Biosensor

## TL;DR

A new biosensor detects anti-SARS-CoV-2 antibodies in human serum with high sensitivity, offering a promising tool for diagnosing and monitoring immunity to COVID-19.

## Contribution

A novel photonic biosensor platform using Bloch Surface Waves for highly sensitive antibody detection in human serum.

## Key findings

- The biosensor achieved clear discrimination of anti-SARS-CoV-2 antibodies at a 1:104 serum dilution in fluorescence mode.
- The platform supports both label-free refractometry and label-based fluorescence detection modes.
- Tests on human serum confirmed the platform's effectiveness for detecting antibodies from recovered COVID-19 patients.

## Abstract

Accurate and sensitive antibody detection remains critical for advanced COVID-19 diagnostics and monitoring SARS-CoV-2 immunity. This study presents a highly sensitive technique for detecting anti-SARS-CoV-2 antibodies in human serum using an integrated photonic sensing platform. The platform utilizes disposable one-dimensional photonic crystal biochips engineered to sustain Bloch Surface Waves. The biochips are integrated into a custom-made optical set-up, which is capable of dual-mode detection: label-free refractometry and label-based fluorescence. Tests on human serum, including negative controls and positive samples from a recovered COVID-19 patient, confirmed the platform’s effective performance. In fluorescence mode, clear discrimination between positive and negative samples was achieved down to a 1:104 serum dilution, with an optimal operating range centered around 1:103 dilution. These results demonstrate the potential of the technique as a highly sensitive and versatile platform for antibody detection, with significant relevance for advanced COVID-19 diagnostics.