Selective immediate detection of Cu²⁺ by a pH-sensitive rhodamine-based fluorescence probe in breast cancer cell-line

A biocompatible fluorogenic chemosensor (N-(3-carboxy acryloyl)) rhodamine B (RHA) comprising a furan-2,5-dione receptor and a rhodamine fluorophore via an iminohydrazine crosslinker has been prepared for more scrutinizing optical properties and utilization in molecular imaging of living cells. The consequences indicated that RHA not only is a good pH indicator in acidic media but also can be used as a great sensitive fluoroionophore with high selectivity. The fluorescence emission of the molecule RHA is quite stable in the presence of 15 diverse cations, 18 anions (especially H₂PO₄^-, S², and F^-), and 5 amino acids with the different functional group as a model, except Cu²⁺ ions with observable emission intensity changing. The Cu²⁺ probe has a dual functional effect, an "on-off" mechanism in solvent media, and an "off-on" mechanism in Phosphate Buffered Saline (PBS) in acidic pH conditions. The detection limits for Cu²⁺ in acetone-water media was 0.69 μM and 0.18 μM in pH = 5.0. Moreover, RHA can fluorescently and colorimetrically image Cu²⁺ ions in acidic and neutral pH with low cytotoxicity in living cells.