Development of a Paper-Based Whole Blood Phenylalanine Assay for PKU Diagnosis and Monitoring in Low Resource Settings

Graduation date: 2016Phenylketonuria (PKU) is a genetic inborn metabolic disorder which inhibits\ud the functional production of the enzyme phenylalanine hydroxylase (PAH). It currently affects one in 15,000 Americans and is the most common amino acid metabolism error found in newborns. Individuals affected with PKU are incapable of metabolizing the amino acid, phenylalanine (Phe) and can face irreversible bodily damage, such as seizures or mental retardation, with elevated concentrations of Phe in the body. PKU is a lifelong disease that requires a regimented diet and total avoidance of foods containing Phe. Current methods for measuring Phe concentrations in blood require routine laboratory tests. It can take several days and even weeks for patients to get the results of these tests. This greatly limits the usefulness of measuring the patient Phe levels using current methods. The availability of these tests are limited to places with testing laboratories where patients can mail dried blood samples, which is generally only in developed nations. A point-of-care (POC) device capable of measuring blood Phe levels in low-resource settings, such as in homes or developing nations, could lower test cost and turn-around time and broaden the accessibility of Phe monitoring for affected individuals.\ud \ud This report describes the conversion of a laboratory-based enzymatic/colorimetric assay (ECA) into a paper-based lateral flow test (LFT) that can detect relevant Phe concentrations in a whole blood sample. The proposed assay uses a well- known, two-step chemical reaction resulting in a colorimetric response that can visually be correlated to Phe concentration. An experiment was first developed to demonstrate assay capabilities with Phe-spiked human plasma in glass fiber and cellulose substrates. A plasma separation membrane was integrated that enabled the assay to accept and process whole blood samples. The assay successfully correlated blood Phe concentrations with the intensity of a visible colorimetric response from a Phe-spiked whole blood sample