employing polymericmicelle assembly for encapsulation of a new enzyme (NQO1)-responsive small molecule was established for facile access to nanoprobes with favorable features in bioimaging, such as good aqueous solubility, enhanced photo-stability and biocompatibility. In the presence of the enzyme NQO1, these nanoprobes underwent ratiometric fluorescence changes from yellow-green fluorescence signals
Here, we report a new Cu2+-selective fluorescent turn-on probe BODIPY-EP, in which the 2-pyridinecarboxylic acid is connected to a 6-hydroxyindole-based BODIPY platform through an ester linkage. The ester bond of BODIPY-EP is selectively hydrolyzed by the reaction with Cu2+ under mild and neutral conditions to generate BODIPY-OH, showing strong characteristic fluorescence of BODIPY-OH. The favorable features of BODIPY-EP towards Cu2+ include fast response, large fluorescence enhancement and high selectivity. We further demonstrated that the membrane-permeable probe reacts with intracellular Cu2+ and exhibits bright fluorescence in living cells.
A 6-hydroxyindole-based BODIPY, named BODIPY–OH, with distinct spectroscopic characteristics is reported. Through a systematic study of the spectroscopic characteristics of BODIPY–OH and BODIPY–O− in various solvents containing an organic base, we found that the light-color of the fluorophore can be tuned over a wide range by changing the polarity of solvent/base combinations. The absorption color of the solution can be tuned over a range of 100 nm and the emission color within a wide range from 571 to 681 nm by simply converting the phenol form of BODIPY–OH to the phenolate form. Fluorescence of BODIPY–O− with high quantum yield shows relatively large Stokes shift in solvent/base combinations, which are ascribed to the excited state deprotonation from (BODIPY–OH)* to (BODIPY–O−)*, followed by emission from the ion form.