Evaluation of Fluorescent Cu Probes: Instant Sensing, Cell Permeable Recognition and Quantitative Detection.

By incorporating a rhodamine spirolactam structure as the recognition site for Cu, two novel probes were synthesized through a connection of rhodamine 6G acylhydrazine and 5-formyl-6-hydroxyl-4-methylcoumarin/2,4-dihydroxybenzaldehyde. In the recognition process of probes towards Cu, the spirolactam ring exhibited opening and closing, accompanying an instant and specific change in fluorescence and in color, which could also achieve a naked-eye and semiquantitative recognition of aqueous Cu besides the fluorescent Cu detection method. Fluorescent analyses and ECV304 cell imaging further revealed the probes' good optical stability, instant response, low toxicity, and membrane permeability, which offers future possibilities for the probes' instant detection and the real-time tracking of Cu in biological systems.