| Abstract | Population assessments of infection and immunity status are critical for public health response to infectious disease. Most microfluidic tools are developed to assess one or the other – few assess both. This study introduces a multiplexed, fully automated digital microfluidic (DMF) platform designed to detect viral protein as a proxy for infection status and host IgG and IgA antibodies as a marker for immunity status. SARS-CoV-2 and patient saliva were used as a model system to evaluate the concept. Specifically, the infection assay relied on nanobody-based capture and detection agents specific to SARS-CoV-2 trimeric spike protein, with a limit of detection (LOD) of 3.8 ng mL⁻¹ in saliva. And the immunity relied on monoclonal antibodies for host IgG and IgA specific to SARS-CoV-2 spike S1 domain, with LODs of 4.8 ng mL⁻¹ and 13.3 ng mL⁻¹ in saliva, respectively. Clinical validation in saliva samples from human subjects experiencing symptoms (n = 14) showed strong correlation with PCR and commercial ELISA, achieving 100% sensitivity and 100% specificity for infection detection and 100% sensitivity with 91.7% and 90.9% specificity for host IgG and IgA, respectively. These results highlight potential applications for the new system as a portable diagnostic tool for outbreak surveillance and public health management, as a step toward preparing for the next global pandemic. |
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