A portable low-cost fluorescence-based quantitative immunosensing platform

By enabling the detection of antibodies, antigens, and metabolites, immunosensing plays a central role in diagnosing and monitoring a wide spectrum of infectious and non-infectious diseases, including avian influenza virus (AIV), post-acute sequelae of SARS-CoV-2 (PASC), and cancer. However, due to the limited analytical performance of portable alternatives, quantitative immunosensing presently depends on costly, centralized laboratory equipment operated by specialists and incurs substantial ongoing expenses for reagents, maintenance, and specimen transport. Here, we present a portable, low-cost, and fully quantitative fluorescence-based immunosensing platform that delivers the performance of established laboratory immunoassays. It can quantify antibodies, antigens, and compatible metabolites in biofluids, while requiring minimal infrastructure, sample volume, and reagents. A coordinated set of innovations enabled these outcomes: hardware advances enabled miniaturized optics and reduced the sample and reagent volumes required per assay, while software advances boosted assay sensitivity and accuracy. We report the first 3D-printed polymer optical housing for fluorescence imaging, and are the first to apply log-logistic probabilistic models to separate fluorescence signals from noise. The device was validated by quantifying anti-AIV antibodies (a biomarker for tracing AIV outbreaks) and anti-SARS-CoV-2 antibodies (a biomarker for monitoring PASC) in avian and human serum, and it has participated in preliminary indoor field tests. Both assays showed performance comparable to or exceeding the published values for commercial assays, while costing less than $0.50 USD per test. By enabling cost-effective point-of-care quantitative immunosensing, this device can potentially monitor disease outbreaks, assess immunity, and improve prognosis and treatment across human and animal diseases.