  In the context of continued spread of coronavirus disease 2019 (COVID-19)
caused by SARS-CoV-2 and the emergence of new variants, the demand for rapid,
accurate, and frequent detection is increasing. Besides, the new predominant
strain, Omicron variant, manifests more similar clinical features to those of
other common respiratory infections. The concurrent detection of multiple
potential pathogens helps distinguish SARS-CoV-2 infection from other diseases
with overlapping symptoms, which is significant for patients to receive
tailored treatment and containing the outbreak. Here, we report a lab-on-a-chip
biosensing platform for SARS-CoV-2 detection based on subwavelength grating
micro-ring resonator. The sensing surface is functionalized by specific
antibody against SARS-CoV-2 spike protein, which could produce redshifts of
resonant peaks by antigen-antibody combination, thus achieving quantitative
detection. Additionally, the sensor chip is integrated with a microfluidic chip
with an anti-backflow Y-shaped structure that enables the concurrent detection
of two analytes. In this study, we realized the detection and differentiation
of COVID-19 and influenza A H1N1. Experimental results show that the limit of
detection of our device reaches 100 fg/mL (1.31 fM) within 15 min detecting
time, and cross-reactivity tests manifest the specificity of the optical
diagnostic assay. Further, the integrated packaging and streamlined workflow
facilitate its use for clinical applications. Thus, the biosensing platform
offers a promising solution to achieve ultrasensitive, selective, multiplexed,
and quantitative point-of-care detection of COVID-19.
