A preclinical biosensor for detecting phenylalanine photometrically in plasma and whole blood samples

Phenylketonuria (PKU) is a metabolic disease resulting from a deficiency in the enzyme phenylalanine hydroxylase, increasing L-Phenylalanine (L-Phe) values in the blood and consequently in the brain. If untreated, PKU leads to neurological damage, which can be prevented by following a diet low in L-Phe. Thus, early detection of PKU in newborns is essential. The disease’s screening and monitoring are centralized in reference centers, which require specialized equipment. However, using these techniques, sample treatment is required before the analysis, and trained personnel must perform and interpret the results. In this work, we present an enzyme-based photometric strategy to measure blood L-Phe. An enzymatic mixture, selective for L-Phe, is immobilized on an UV transparent well, and the amount of consumed co-factor is monitored at 340 nm. Standard plasma and whole blood samples were chosen to pre-validate the sensor. The samples were spiked with an increasing amount of L-Phe, accurately discriminating between physiological and pathological L-Phe concentrations. The strategy can be easily extended to analyzing other samples, such as urine or sweat. The proposed photometric system allows to analyze up to 16 samples simultaneously within a matter of hours. The measurements are relatively fast, versatile, cost-effective, and easy to carry out.