Highly selective fluorescent probe based on AIE for identifying cysteine/homocysteine

Area of Science:

• Analytical Chemistry
• Biochemistry
• Chemical Biology

Background:

• Cysteine (Cys) and homocysteine (Hcy) are crucial biomolecules involved in physiological homeostasis and disease pathogenesis.
• The presence of high glutathione (GSH) levels poses a significant challenge for the selective detection of Cys and Hcy.

Purpose of the Study:

• To develop a novel fluorescent probe for the selective and sensitive detection of Cys and Hcy in biological systems.
• To investigate the mechanism of action and assess the performance of the developed probe.

Main Methods:

• Synthesis of a novel Aggregation-Induced Emission (AIE) fluorescent probe, SQM-NBD, by conjugating NBD to SQM-OH.
• Investigation of the probe's response mechanism to Cys/Hcy in the presence of GSH.
• Determination of the probe's sensitivity (Limit of Detection - LOD) for Cys and Hcy.
• Application of the probe for fluorescence imaging of Cys/Hcy in HeLa cells.

Main Results:

• The SQM-NBD probe exhibits minimal intrinsic fluorescence but is activated by Cys/Hcy.
• The probe selectively detects Cys/Hcy by releasing SQM-OH and Cys/Hcy-NBD, with Cys/Hcy further quenching SQM-OH fluorescence.
• Achieved high sensitivity with LODs of 54 nM for Cys and 72 nM for Hcy.
• Successfully demonstrated fluorescence imaging of Cys/Hcy in HeLa cells.

Conclusions:

• SQM-NBD is a highly sensitive and selective fluorescent probe for detecting Cys and Hcy.
• The probe's mechanism involves a combination of Michael addition and ion-rich environment interactions.
• SQM-NBD shows significant potential for identifying Cys/Hcy under physiological and pathological conditions, including cellular imaging.