Highly Selective and Sensitive Fluorescent Biosensor for the Detection of Serotonin and its Metabolite by Eu3+-Doped Metal-Organic Framework

Monoamine neurotransmitters such as L-epinephrine (EPI), norepinephrine (NE), dopamine (DA), and serotonin (ST) are important biomarkers for neurological diseases. However, specific detection of a single monoamine neurotransmitter is challenging. In this work, a water-stable fluorescent biosensor, Eu 3+ -doped UiO-66 metal-organic framework ( EuUPDC ), is constructed for specific recognition of ST and its metabolite, 5-hydroxyindole-3-acetic acid (5-HI-3-AA). The detection limits of EuUPDC for ST and 5-HI-3-AA are 0.013 μM and 0.15 μM, respectively. The LOD value for ST is 10-fold improvement compared to the reported fluorescent sensors. Importantly, the biosensor specifically recognizes ST at very low concentrations in the presence of co-existing monoamine neurotransmitters. Furthermore, the EuUPDC biosensor is successfully applied for the determination of ST and 5-HI-3-AA in human serum and urine with good recoveries. Finally, a EuUPDC -embedded test strip is fabricated and portable smartphone-assisted RGB color values are effectively integrated with a lowest detectable value of 0.6 μM for ST and 6.7 μM for 5-HI-3-AA. The designed biosensor EuUPDC has great potential for the quantitative determination of ST and 5-HI-3-AA, and applicable for early diagnosis of neurological diseases