Nanophotonic biosensors for COVID-19 detection: advances in mechanisms, methods, and design

The growing societal impact of coronavirus disease 2019 (COVID-19) has underscored the urgent need for innovative strategies to address the ongoing challenges posed by the pandemic. While rapid therapeutic interventions remain critical for short-term mitigation, equally vital is the development of accessible and efficient diagnostic tools to curb viral transmission. In this context, optical sensing technologies have emerged as foundational tools for detection and diagnosis, owing to their rapid response, user-friendliness, and adaptability. These attributes strengthen their indispensable role in identifying severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the causative agent of COVID-19. This review systematically outlines the structural components of SARS-CoV-2 virions and their respective biological functions, classifies optical biosensors according to their underlying principles and evaluates the advantages and limitations of each methodology in real-world diagnostic applications. By addressing current detection challenges, these optical platforms not only enhance our capacity to manage SARS-CoV-2 but also establish a framework for deploying optical sensing technologies in future pandemic scenarios.