A BODIPY-Based Probe Enables Fluorogenicity via Thiol-Dependent Modulation of Fluorophore Aggregation

Area of Science:

• Chemical Biology
• Fluorescent Probes

Background:

• BODIPY fluorophores are widely used in biological research.
• Aggregation of BODIPY probes in aqueous solutions often quenches their fluorescence.
• Aggregation-caused quenching (ACQ) significantly impacts spectroscopic properties and limits probe utility.

Purpose of the Study:

• Investigate the aqueous behavior of a para-maleimide-substituted meso-phenyl BODIPY (p-MB).
• Explore the potential of p-MB as a turn-on fluorescent probe.
• Elucidate the mechanism behind fluorescence restoration upon reaction with specific substrates.

Main Methods:

• Characterization of p-MB in organic and aqueous media.
• Spectroscopic analysis (fluorescence spectroscopy) to monitor probe behavior.
• Investigation of probe reactivity with thiols and TCEP, including those with adjacent ionizable groups.

Main Results:

• In aqueous solution, p-MB exhibits aggregation-caused quenching (ACQ), leading to reduced fluorescence.
• p-MB shows a significant turn-on fluorescence signal upon reaction with thiols and TCEP.
• Fluorescence enhancement is maximized when reacting with substrates containing adjacent ionizable groups, indicating disaggregation-induced emission (DIE).
• Probe reactivity is diminished after stable aggregate formation, suggesting a target-mediated inhibition of aggregation.

Conclusions:

• The study highlights the aggregation issue of BODIPY probes in aqueous environments.
• p-MB demonstrates a turn-on sensing capability through a mechanism involving target-mediated inhibition of probe aggregation, rather than dispersion from preformed aggregates.
• This work proposes a revised understanding of the disaggregation-induced emission (DIE) mechanism for fluorescent probes.