Quantitative fluorescence detection of phenylalanine in blood spots on filter paper

Phenylketonuria is a genetic disease, which causes the metabolization disorder of phenylalanine, this disorder would damage the neural system of infants as a result of the accumulation of phenylalanine in blood. Therefore, it is of great importance to diagnose and treat phenylketonuria as early as possible for newborns. The aim of this paper is to develop a fluorescence detection system to measure blood phenylalanine concentration of new-born infants. In this design, a high luminance ultraviolet LED is used for excitation source, and a kind of bifurcated optical fiber assembly is applied for conduction of light. The excitation source is filtered and coupled into quartz fibers of the bifurcated fiber assembly for conduction of light to excite the fluorescence of phenylalanine in blood sample. The collected fluorescence is transmitted along the glass fibers of the assemblies and coupled to a photomultiplier tube. The fluorescence is filtered with 470~500 nm band-pass filter to subdue scattered excitation light and to limit the spectral width of the detected fluorescence. By the comparison with a standard instrument, the new system with low power consumption, low cost and small size is also proven sensitive and accurate, which meets the demand of clinical phenylketonuria screening.