Project Summary Organophosphate (OP) pesticides poisoning is a major environmental and occupational health problem worldwide due to its acute or chronic toxicity. Rapid and accurate detection of personal exposure to OP pesticides is critical to both research and clinical care for victims. However, this detection remains highly variable across commercially available assays, e.g., the Ellman method, and such assays may also not adequately detect low but clinically relevant levels of exposure biomarkers. Moreover, these assays are generally performed in the centralized laboratories, and is slow and expensive. These deficits translate into missed opportunities for the timely initiation of the most appropriate treatment and interventions for acutely or chronically poisoned victims. A simple, rapid, non- or minimally invasive biomonitoring tool for onsite sensitive and accurate detection of personal exposure to OP pesticides is highly desirable and fits the interest of NIEHS exposure program. This STTR phase I project is to develop an innovative integrated smartphone/nanosensor platform for onsite rapid and sensitive detection of OP exposure using a tiny drop of finger-stick blood. This nanosensor will take advantage of nanotechnology and wireless technology and utilize an important biomarker, blood cholinesterase, for the detection of personal OP exposure and the resulted tool has the potential to serve as mHealth for environmental and occupational workers. The research will determine the detection limit, sensitivity, dynamic range, and other key performance metrics of the sensing platform using blood samples in vitro dosed with typical pesticides and validate the platform in field using finger-stick blood samples from farmworkers, and demonstrate the feasibility of the platform for sensitive and accurate detection of exposure to OP pesticides. The resulted nanosensor would be a simple, rapid, cost-effective, and minimally-invasive, point-of-care biomonitoring tool for accurate personal exposure assessment and for on-site rapid detection of exposure to OP pesticides. Thus, this novel sensing platform could serve as a personal meter for self-test just like a glucose meter and could also be used in field, physician's office, bedside, and emergency room.