An EuL¹₃ with multi-recognition site used as luminescent biosensors for efficiently monitoring exercise therapy for...

Depression is a mental disorder characterized by high mortality and recurrence rates, with diagnosis primarily relying on various scales and lacking a gold standard. Neurotransmitters such as dopamine (DA), 5-hydroxytryptamine (5-HT), epinephrine (E), and norepinephrine (NE) are established biomarkers for depression. Therefore, there is a significant need to develop real-time, sensitive sensors for these compounds. Due to the complexity of biological environments, improving the sensitivity of biosensors remains a critical challenge in this field. To enhance sensor sensitivity, we introduced pyridyl groups-capable of forming π-π stacking, cation-π and hydrogen bonding interactions with these biomarkers-onto β-diketone ligands, which can undergo nucleophilic interaction with amino groups. The resulting ligands were then coordinated with lanthanide ions through directed self-assembly, forming single-nuclear lanthanide sensors with multiple reactive sites. The mononuclear structure improves the sensor's solubility, compared with the benzene-ring-based sensor EuL²₃, the pyridine-incorporated sensor EuL¹₃, featuring additional interaction sites, reduces the detection limit for DA from 12.71 nM to 4.49 nM and shortens the response time from 0.41 s to 0.25 s. The enhanced intermolecular interaction between EuL¹₃ and the biomarker is verified by ¹H NMR and NOESY spectroscopy. Furthermore, we applied this sensor to evaluate the intervention effects of moderate intensity continuous training (MICT) in alleviating depression-like behaviors in chronic unpredictable mild stress (CUMS)-induced mice. When hippocampal and medial prefrontal cortex (mPFC) homogenates were added to the EuL¹₃ solution, the luminescence intensity of EuL¹₃ significantly decreased, yielding results consistent with enzyme-linked immunosorbent assay (ELISA). These results demonstrates the potential of EuL¹₃ for application in depression diagnosis and therapeutic efficacy assessment.