The COVID-19 pandemic caused by the SARS-CoV-2 virus has brought global healthcare systems to their knees. The spike protein on the surface of the virus is a critical component for viral entry into human cells and therefore is a prime target for diagnosis and therapeutics. In recent years, the integration of photonic technology with biosensors has emerged as a promising approach due to its high sensitivity, specificity, and real-time detection capabilities. Optical fibres are one of the most versatile platforms for photonic technology-based biosensors, owing to their small size, low cost, and compatibility with various transduction methods. In this work, we present photonic technology based on optical fibres for the detection of the spike protein present in the SARS-CoV-2 virus. The proposed method involves the use of ad hoc synthesized peptides that specifically bind to the spike protein. The synthesized peptides are immobilized on the surface of the external face of an asymmetric Fabry-Perot cavity fabricated at the end face of a standard optical fibre, which acts as a biosensor. The presence of the spike protein in the sample causes a change in the refractive index, which is detected as variations in the visibility of the spectrum generated in Fabry-Perot cavity. The experimental results carried out have detected spike protein on buffered solutions with an LOD of 0.3 ng/ml. The proposed method offers several advantages over existing biosensors, including high sensitivity, real-time detection, and ease of integration into existing diagnostic platforms. We believe that the proposed photonic technology-based approach can significantly contribute to the development of biosensors for the early diagnosis of COVID-19 and other diseases.

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