Although nanomaterials have tremendous potential to improve human health, it has remained surprisingly elusive to leverage their properties to produce real clinical impact. One of the most promising applications of nanoparticles is in sensors for detection of analytes. For sensors that need to be performed at the point of care (POC), one large barrier to unlocking the potential of nanoparticles is the traditional need for complex detectors, such as microscopes, optical filters, charged-coupled detectors, and photomultiplier tubes. While suitable for a well-equipped laboratory, such instrumentation is not feasible in resource-limited settings where some of the most medically dire patients reside. Here, we propose to develop and field-test a novel POC diagnostics device that centers on a signal amplification strategy where silver salts are reduced to solid silver, in a reaction catalyzd by gold nanoparticles conjugated to detection antibodies. In this proposal, we propose to develop a portable instrument that can read out the resultant optical signal, to help move nanoparticles to being used in real practical POC sensors. PUBLIC HEALTH RELEVANCE: The goal of this grant is to leverage the unique properties of nanoparticles to build a low-cost portable instrument that can read out the optical signals catalyzed by nanoparticles.