A Water-Soluble Multifunctional Probe for Colorimetric Copper Sensing, Lysosome Labelling and Live-Cell Imaging

We report a water-soluble fluorescence and colorimetric copper probe (LysoBC1); this system can also serve for lysosome labeling and for the dynamic tracking of Cu²⁺ in living cells. The sensing mechanism takes advantage of the synergic action by the following three components: i) a lysosome targeting unit, ii) the spirolactam ring-opening for the selective copper chelation and iii) the metal-mediated hydrolysis of the rhodamine moiety for fluorescence enhancement. In aqueous environment the molecule acts as a fluorescent reversible pH sensor and as colorimetric probe for Cu²⁺ at physiological pH; the hydrolysis of the copper targeting unit resulted in a 50-fold increase of the fluorescence intensity. Most importantly, in vitro cell analyses in undifferentiated (SH SY5Y) and differentiated (d-SH SY5Y) neuroblastoma cells, LysoBC1 is able to selectively accumulate into lysosome while the copper binding ability allowed us to monitor intracellular copper accumulation into lysosome.