PROJECT SUMMARY Despite keen interests in early diagnosis of Alzheimer’s disease & its related dementias (AD/ADRD), which faces a multitude of underlying nuanced and mixed pathologies, the progress has been hampered by insufficient sensitivity and low specificity to the pathology. New molecular assays include cerebrospinal fluid measurements and brain amyloid plaque imaging through positron emission tomography (PET). However, these techniques face limitations as they either require lumbar punctures, have insufficient sensitivity for early detection, or are too expensive for wider adoption. As a result, there is an unmet need in timely and cost-effective AD diagnostics. Detection of disease biomarkers in the blood, known as “liquid biopsy”, can in principle improve the accuracy of measuring nearly invisible diseases. Exosomes are cell-excreted extracellular vesicles that contain surface proteins and genetic materials (DNA and RNA) that reflect the characteristics and make-up of the parental cells. Analyzing brain-derived exosomes (BDE) would therefore provide direct insight into the state of the parental cells of neuronal and glial origins. For Alzheimer’s disease & related dementias (AD/ADRD) diagnostics in particular, recent evidences have shown that several pathological surface proteins and cargo micro-RNAs are differentially expressed in BDE in AD/ADRD. Therefore, unlocking the wealth of information in circulating BDE can potentially cause a paradigm shift. However, current limitations for profiling BDE are the following: (1) significant blood volume is needed; (2) sophisticated protocols; (3) label-free sizing/counting lacks molecular specificity; (4) provide highly averaged results with high background from normal exosomes, thus leading to poor sensitivity. (5) provide “partial” information: either surface antigen or cargo DNA/RNA, but not both. All of the above has hampered the development of further understanding of circulating BDE associated with AD/ADRD and a potential blood test for AD/ADRD diagnostics. In this Administrative Supplement, we propose to extend the microfluidic arrayed nanoplasmonic sensor & actuator (MANSA) platform in the original R01 to single BDE profiling. The MANSA platform will enable: (1) streamlined operation from capturing to profiling. (2) improved sensitivity by digital counting via dynamic imaging. (3) improved specificity by profiling multiple surface proteins and cargo microRNA associated with AD pathologies. A high-resolution, exosome array with multiplex surface protein and cargo microRNA profiles will facilitate high dynamic range enumeration and boost sensitivity in blood-based AD diagnostics and accentuate high-value circulating AD biomarkers. The proposed technology would lead to a cost-effective, point-of-care-friendly, translational platform.