Quantitative fluorescence ratio imaging of intralysosomal chloride ions with single excitation/dual maximum emission.

Fluorescence ratio imaging is currently being used to quantitatively detect biologically active molecules in biosystems; however, two excitations of most existing fluorescent ratiometric probes account for cumbersome operating conditions for imaging. Thus, a fluorescent ratiometric probe, 6-methoxyquinolinium-dansyl (MQ-DS), for Cl(-) with single excitation/dual maximum emission has been developed. MQ-DS can preferably localize into lysosomes and display excellent photostability. Upon excitation at a single wavelength, it responds precisely and instantaneously to changes in Cl(-) concentrations, and it can be conveniently utilized to implement real-time fluorescence ratio imaging to quantitatively track alterations in Cl(-) levels inside cells treated under various pH conditions, and also in zebrafish with acute wounds. The successful application of the new probe in bioimaging may greatly facilitate a complete understanding of the physiological functions of Cl(-) .