Monitoring Metabolites Using an NAD(P)H-sensitive Polymer Dot and a Metabolite-Specific Enzyme.

We introduce an NAD(P)H-sensitive polymer dot (Pdot) biosensor for point-of-care monitoring of metabolites. The Pdot is combined with a metabolite-specific NAD(P)H-dependent enzyme that catalyzes the oxidation of the metabolite, generating NAD(P)H. Upon UV illumination, the NAD(P)H quenches the fluorescence emission of Pdot at 627 nm via electron transfer, and also fluoresces at 458 nm, resulting in a shift from red to blue emission at higher NAD(P)H concentrations. Metabolite concentration is quantified ratiometrically-based on the ratio of blue-to-red channel emission intensities, with a digital camera-with high sensitivity and specificity. We demonstrate phenylalanine biosensing in human plasma for a phenylketonuria screening test, quantifying several other disease-related metabolites (lactate, glucose, glutamate, and β-hydroxybutyrate), and a paper-based assay with smartphore imaging for point-of-care use.