A two-photon probe for Al3+ in aqueous solution and its application in bioimaging

A salicylimine probe L with a simple structure has been researched more in-depth on fluorescence sensor properties based on two-photon (TP) absorption. L displays excellent selective turn-on fluorescence response for Al3+ in hexamethylenetetramine-buffered (HMTA) aqueous solution (0.3M, pH=5.8) under one-photon (OP) excitation. With the help of OP fluorescence, TP fluorescence titration, UV-spectra titration and Job's plot, the stoichiometric ratio of L with Al3+ was determined to be 1:1. The coordination sites and the coordination mechanism of L with Al3+ were analyzed in detail through 1H NMR data. Not only with a detection limit of 5.2×10−9M in vitro, but also the probe has been successfully used in the live cells and tissues for the imaging of Al3+ with TP fluorescence microscopy due to the enlarged TP cross section, providing a novel testing method for measuring Al3+ in solution or cell tissue with low autofluorescence and cytotoxicity. [Display omitted] •Excellent selective turn-on fluorescence response for Al3+ can be observed.•The measurement of the fluorescence signals is free from organic solvents.•Al3+ make the probe display enlarged TP cross section.•It can be successfully applied in live cells for two-photon bioimaging of Al3+.