Abstract The long-term objective of this proposal is to further develop a photochemical signal amplification method (PSAM) for increasing the sensitivity of conventional enzyme-linked immunosorbent assays (ELISA) for determination of biomarkers for various neurodegenerative diseases, such as Alzheimer’s Disease (AD). Immunoenzymatic methods such as ELISA are widely used in biology and medicine for drug screening, for detecting viruses (including coronaviruses), bacteria, and biomarkers, particularly cytokines and interleukins for cancer and immunological disorders, and biomarkers for neurodegenerative diseases. They are routinely used in manual, semi-automated, and automated systems where high volumes of tests are performed. However, in many cases the sensitivity of ELISA is inadequate. Some of the key biomarkers for early diagnosis of AD include three cerebrospinal fluid (CSF) biomarkers: amyloid ß-42 (Aß-42), which causes formation of oligomeric plaques, total tau (t-tau), and phosphorylated tau (p-tau) (which increases intracellular neurofibrillary tangles (NFTs). To date, there is no sensitive and cost- effective method for the quantification of these three proteins, hindering the diagnosis and progression monitoring of AD. Existing highly sensitive methods are cumbersome and expensive. Therefore, there is an increased necessity for a common ELISA platform to detect low levels of Aß-42, t-tau, p-tau and other biomarkers for various neurodegenerative diseases that is both inexpensive and simple enough to not require specialized laboratory equipment. In our Phase II project, we propose to further develop a very sensitive and inexpensive immunoassay platform for detection of biomarkers for various neurodegenerative diseases. In particular, we will 1) design and manufacture a pre-production PSAM illumination device; 2) design and develop a PSAM detection system kit, ELISA + PSAM kits for detection of Aß-42, t-tau, p-tau, BDNF and proBDNF; 3) conduct extensive performance evaluation studies towards Research Use Only applications of the PSAM products.