TAPP-based fluorescent probes for selective cysteine detection: insights into structure-reactivity relationships

Area of Science:

• Organic Chemistry
• Analytical Chemistry
• Biochemistry

Background:

• Cysteine (Cys) is a vital amino acid involved in numerous biological processes.
• Developing selective and sensitive fluorescent probes for Cys detection is crucial for biological and medical research.
• Structure-reactivity relationships in fluorescent probes influence their sensing capabilities.

Purpose of the Study:

• To design and synthesize TAPP-based fluorescent probes with varying functional groups (aldehyde, malononitrile, cyanoacrylate) for Cys sensing.
• To investigate the structure-reactivity relationships governing Cys detection.
• To develop a sensitive and selective fluorescent probe for Cys detection.

Main Methods:

• Synthesis of TAPP-based π-conjugated fluorescent probes.
• Photophysical characterization in various solvents (THF, DCM, DMSO).
• Spectroscopic analysis (¹H NMR, HRMS) to elucidate the sensing mechanism.
• Evaluation of probe performance including response kinetics, selectivity, linear range, limit of detection (LOD), and pH stability.

Main Results:

• The aldehyde-functionalized TAPP probe exhibited a "turn-on" fluorescence response to Cys via thiazolidine ring formation.
• The probe demonstrated rapid response (approx. 50 s), high selectivity for Cys over GSH, NAC, and other species.
• A low LOD of 0.37 µM was achieved with a linear response range of 0-15 µM.
• Effective operation under near-physiological pH conditions was confirmed.

Conclusions:

• A novel, sensitive, and selective fluorescent probe for cysteine detection has been developed.
• The study provides mechanistic insights into how terminal group functionality impacts TAPP-based probe behavior.
• The developed probe shows practical applicability for Cys detection in biological samples.