The broader impact/commercial potential of this Small Business Innovation Research (SBIR) Phase I project addresses an urgent need for a rapid and convenient method to monitor blood phenylalanine levels for patients with phenylketonuria, or PKU for short. Patients with PKU are unable to catabolize phenylalanine and therefore have elevated, toxic levels. These patients are treated with a severely protein-restricted diet and other potential medications. Since excess phenylalanine results in neurologic injury, and inadequate phenylalanine results in protein malnutrition, the diet of patients must be carefully balanced. This balance can only be accomplished by tracking blood phenylalanine levels, which fluctuate throughout the day. Currently the turnaround time of laboratory tests is 5 to 7 days, and sometimes longer, during which patients may experience prolonged episodes of behavioral and neurocognitive morbidities. PKU is a lifelong genetic disorder and requires constant tuning of diet therapy. The annual societal cost for taking care of patients with PKU can range from $15,000 to $200,000; this disease causes irreversible damage and high costs of care when improperly managed. The proposed project will develop a new monitor for these patients to prevent long-term effects. This Small Business Innovation Research (SBIR) Phase I project will develop a new rapid, phenylalanine monitor for patients with phenylketonuria. Rapid quantification of blood phenylalanine levels to improve patient outcomes. The device will also be a cost effective alternative to the standard of care as it is today. This device consists of a test strip and a test device. The test strip accepts a blood drop from a finger prick. The test strip contains various chemistries that condition the blood sample prior to optically analysis by the test device. The test device implements spectroscopy to interrogate the test strip as it determines phenylalanine quantity. The focus of this project is to optimize the product design and system algorithm. The proposed work enables cost-effective manufacturing and deployment of the device to the end user; the end goal of this project is to develop a simple prototype.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.