Coumarinocoumarin-Based Two-Photon Fluorescent Cysteine Biosensor for Targeting Lysosome

Area of Science:

• Biochemistry
• Chemical Biology
• Fluorescence Spectroscopy

Background:

• Coumarin derivatives offer excellent optical properties due to their large conjugate planes.
• Developing targeted fluorescent biosensors is crucial for studying biological processes.
• Cysteine (Cys) plays vital roles in cellular functions, and its dysregulation is linked to diseases.

Purpose of the Study:

• To design and synthesize a novel coumarinocoumarin-based fluorescent probe (CCy) for sensitive and selective detection of cysteine.
• To evaluate the probe's performance in biological samples, including cells and live animals.
• To demonstrate the probe's lysosomal targeting capability.

Main Methods:

• Synthesis of the coumarinocoumarin-based probe (CCy) through a three-step procedure.
• Characterization of the probe's fluorescence response to cysteine (Cys) and other amino acids under physiological conditions.
• Application of the probe for fluorescence imaging in HeLa cells and mice organ tissues, and quantitative determination in animal serum.

Main Results:

• The CCy probe exhibited a high sensitivity and fluorescence turn-on response specifically to cysteine over homocysteine and glutathione.
• Remarkable fluorescence enhancement at 520 nm was observed upon Cys addition.
• Successful fluorescence imaging and quantification of Cys in cells and live mice demonstrated the probe's cell permeability and biocompatibility (viability >80%).
• Lysosomal targeting of the probe was validated.

Conclusions:

• The CCy probe is the first lysosomal targeting fluorescent biosensor for cysteine.
• CCy offers a sensitive, selective, and biocompatible platform for Cys detection in vitro and in vivo.
• This probe facilitates real-time monitoring of Cys in biological systems, particularly within lysosomes.