Advances in Coumarin-Based Dual-Mode Probes for Bioimaging and Cytotoxicity Evaluation: A Review

Coumarin derivatives have emerged as one of the most versatile fluorophore families in chemical biology. Their compact heterocyclic architecture allows facile functional modifications, enabling the rational design of dual-mode probes capable of providing both colorimetric and fluorescence outputs. Over the last decade, coumarin-based sensors have gained considerable attention for detecting biologically and environmentally relevant metal(II) ions. Beyond analytical sensing, the biological utility of coumarin-based systems has expanded significantly, particularly in cytotoxicity evaluation and live-cell imaging. Numerous studies from demonstrate successful intracellular metal-ion visualization across a wide spectrum of cellular models, including HepG2, HeLa, A375, MCF-7, KYSE30, HEK293T, PC12, MDA-MB-231, HEK293, HCT116, H9c2, C6, HeLa S3, A549, and RAW 264.7 cells. Coumarin probes have also been effectively applied in <i>C. elegans</i>, zebrafish, and glassfish larvae, enabling whole-organism imaging and dynamic tracing of metal(II) distribution. The aim of this review is to systematically summarize advancements in coumarin-based dual-mode probes from 2018 to 2025, with emphasis on their structural design, sensing performance toward metal(II) ions, biological compatibility, and imaging applications across diverse cell lines and organism models.