Pyridine-NBD: A homocysteine-selective fluorescent probe for glioblastoma (GBM) diagnosis based on a blood test.

The precise in vitro diagnosis requires a high selectivity and sensitivity for a diagnostic agent. In this respect, fluorescent diagnostic probes have attracted attention in various clinical fields. Herein, we disclosed a tailor-made fluorescent homocysteine probe (NPO-Pyr) based on pyridine-thiol coordination and amine-addition. To date, Hcy has been recognized as an excellent biomarker for various diseases, but there still remain some limitations in detecting of Hcy due to its structural similarity to Cys. In this study, we developed a new fluorescent diagnostic probe for monitoring Hcy by incorporating 4-hydroxy-pyridine moiety into the skeleton of the NBD fluorophore. The incorporated pyridine moiety could coordinate with the thiol group at Hcy, followed by the amine-addition reaction (12 kJ/mol). Based on this rationale, NPO-Pyr responded to Hcy and exhibited turn-on properties with high selectivity and sensitivity (LOD: 0.084 ppm), and a fast-response time (<5 min). Furthermore, NPO-Pyr could predict the formation of glioblastoma (GBM) at an early stage through sensing Hcy in blood plasma (vs. healthy group, ∗∗∗∗P < 0.0001). Our findings have a significant importance across various fields from basic science to clinical translation, and we strongly believe that NPO-Pyr has the potential to fully replace the current complex GBM diagnostic process as a simpler in vitro agent.