Photothermal-Contrast Method Based on In Situ Gold Nanostructure Formation for Phenylalanine Detection in Human Blood

An innovative approach based on photothermal contrastto enhanceanalytical sensitivity of enzymatic phenylalanine detection at a solidsurface was demonstrated. Gold nanoparticles in situ produced by the reduced form of nicotinamide adenine dinucleotide,which is generated by an enzymatic reaction, exhibit an excellentphotothermal effect upon green-light stimuli. The enzymatic reactionand the nanoparticles process formation were optically investigated.A sensing range of 10-1000 & mu;M with a detection limitof 3.6 & mu;M for phenylalanine detection were demonstrated. Thetesting with blood samples collected from phenylketonuria patientstogether with concurrent comparison through tandem mass spectrometryhave confirmed the good analytical performances and the robustnessand utility of the proposed photothermal-contrast approach for furtherintegration on clinical devices.