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Accumulating evidence suggests that cytokine storm syndrome (CSS) induced by the SARS-CoV-2 may be the ultimate cause of acute respiratory distress syndrome (ARDS), resulting in severe outcomes of COVID-19 infection and potentially death. Elevated levels of serum interleukin 6 (IL-6) correlate with the occurrence of respiratory failure, ARDS, and adverse clinical outcomes in many COVID-19 patients. The currently available clinical cytokine tests are costly, time-consuming, and require skilled technicians to execute. There is an unmet need for rapid, affordable, robust, and sensitive tests for cytokine levels. Therefore, this study aimed to develop a cost-effective system for quantitative detection of cytokines that can be used in the point-of-care (POC) format within a few minutes of blood collection. Our approach combines detection based on laser-induced breakdown spectroscopy with a lateral flow immunoassay (LIBS-LFIA) to deliver a quantitative clinical analysis platform with multiplexing capability. Lanthanide-complexed polymers (LCPs) were selected as the labels to provide optimal quantitative performance when sensing signals from the test lines of LFIAs. For a prototype implementation and a proof-of-concept, we targeted IL-6 as it is one of the most critical pro-inflammatory cytokines. Our initial LIBS-LFIA biosensor achieved a limit of detection (LOD) of 0.2298 μg/mL of IL-6 within 15 minutes and further sensitivity increase is possible with optimization. Regardless, since high levels of IL-6 are reported for patients in crisis, this is more than adequate to identify patients with highly elevated cytokine levels. Our research provides evidence that rapid and accurate detection of cytokines for clinical diagnosis and prognosis of COVID-19 and other pathogenic infections using LIBS is highly feasible and compatible with the POC format.
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