Fluorescence sensing of pentachlorophenol in tap water using natural C-Phycocyanin

Pentachlorophenol (PCP), a highly toxic and bioaccumulative chlorinated phenol, remains a persistent threat in aquatic ecosystems due to its widespread use and environmental stability. In this study, a novel, eco-friendly, and label-free fluorescence-based sensing platform utilizing unmodified C-phycocyanin (CPC) - a naturally fluorescent, water-soluble protein - for the selective and sensitive detection of PCP in aqueous media was developed. The method exploits direct fluorescence quenching of CPC, exhibiting a clear concentration-dependent emission decrease at 644 nm with excellent linearity and reproducibility. Unlike conventional approaches relying on nanomaterials or chemically modified probes, this method employs a natural biopolymer without derivatization or signal amplification. The developed method achieved a linear detection range of 0.9-31.1 μg.mL^-1, with a limit of detection (LOD) of 0.0780 μg.mL^-1 and a limit of quantification (LOQ) of 0.2599 μg.mL^-1. Among 28 tested analytes, only PCP caused significant quenching, highlighting the exceptional selectivity of the system. Molecular docking analysis supported these findings, revealing that PCP interacts with key residues in the β-subunit chromophore-binding pocket of CPC, consistent with the observed fluorescence quenching. Validation through spike-recovery experiments and GC-MS comparisons confirmed the method's analytical accuracy and practical applicability. This sustainable sensing approach not only broadens the scope of natural protein-based probes in analytical science but also provides an environmentally responsible platform for real-time monitoring of persistent pollutants in aquatic environments.