POJECT SUMMARY Traumatic brain injury (TBI) causes a number of deaths and permanent disability. Today 5.3 million people live with disability caused by TBI in U.S. Typically, TBI is initially assed by the Glasgow Coma Scale on hospital admission and routine neurologic examination. Computed tomography (CT) scanning and magnetic resonance imaging (MRI) are used for confirmatory testing. However, CT and MRI are not always available for every visitor for initial screening at emergency department; and there is no CT and MRI in the pre-hospital settings. Measurement of biomarkers in blood can provide an alternative, cost- effective and rapid route to screen TBI. In 2018, the U.S. Food and Drug Administration (FDA) authorized marketing of blood testing of two diagnosis biomarkers, ubiquitin c-terminal hydrolase-L1 (UCH-L1) and glial fibrillary acidic protein (GFAP), to evaluate TBI. Also, neuron-specific enolase (NSE) has been extensively investigated as a diagnosis blood biomarker for TBI. But there is no any commercial portable in vitro diagnostic tool to rapidly measure these biomarkers in blood in the emergency department and prehospital settings. Recently the PI developed a point-of-care (POC) prototype device that is able to rapidly measure TBI biomarkers in plasma and blood. To bring this prototype POC device to the clinical use, it will require at least three steps: (i) analytical validation; (ii) clinical validation; and (iii) FDA approval and 510(k) clearance. Analytical validation of the prototype device is the first step, which has not been done yet, but it is necessary to accomplish prior to clinical validation. The objective of project is to perform analytical validation of the paper-based lateral flow strip (PLFS) for detection of TBI diagnosis biomarkers in blood, in which surface-enhanced Raman scattering (SERS) is utilized for sensing signal transduction. Three types of PLFS will be used to measure three most recognized TBI diagnosis biomarkers including NSE, UCH-L1 and GFAP with assistance of a portable Raman detector, respectively. Each TBI biomarker can be detected individually with a small volume (around 35 µL) of blood sample within 36 minutes. With establishment of appropriate quality control and improvement procedures, the performance of PLFS will be validated analytically in terms of accuracy, precision, analytical sensitivity, reportable range, and selectivity. This application is in response to the NIH Program Announcement of PAR-18-550 (analytical validation) instead of PAR-18- 548 (clinical validation). If successful, such an inexpensive and rapid diagnostic POC tool will change practice in TBI diagnosis in the emergency department and pre-hospital settings. It will reduce unnecessary CT scans, increase the accuracy of TBI diagnosis, save costs, and enable earlier intervention aimed at mitigating both short and long term sequelae.