NIR-Sensitive Squaraine Dye-Peptide Conjugate for Trypsin Fluorogenic Detection.

Area of Science:

• Biochemistry
• Analytical Chemistry
• Materials Science

Background:

• Trypsin is a recognized biomarker for colorectal, gastric, and pancreatic cancers.
• Accurate and rapid detection methods for trypsin are essential for disease diagnosis.
• Current detection methods may lack the required sensitivity, speed, or cost-effectiveness.

Purpose of the Study:

• To design and synthesize a novel near-infrared (NIR)-sensitive dye-peptide conjugate (SQ-3 PC).
• To develop a fluorescence ON/OFF sensing strategy for sensitive and selective trypsin activity monitoring.
• To evaluate the photophysical properties and sensing performance of the developed probe.

Main Methods:

• Synthesis of unsymmetrical squaraine dyes (SQ-1, SQ-2, SQ-3) and a dye-peptide conjugate (SQ-3 PC).
• Photophysical characterization including absorption and fluorescence spectral investigations in different solvents (water, DMSO).
• Evaluation of trypsin-specific probe performance, including fluorescence quenching efficiency, FRET/AIQ contributions, and fluorescence recovery upon hydrolysis.

Main Results:

• SQ-3 PC exhibited enhanced dye aggregation and pronounced fluorescence quenching in water compared to DMSO.
• The probe demonstrated a 61.8% fluorescence quenching efficiency, dominated by FRET over AIQ.
• Trypsin-mediated hydrolysis rapidly recovered quenched fluorescence (5-fold increase in 30 min).
• SQ-3 PC functions as a trypsin enzyme-specific fluorescence biosensor with linearity up to 30 nM, LOD of 1.07 nM, and LOQ of 3.25 nM.

Conclusions:

• The developed SQ-3 PC probe offers a sensitive and selective method for real-time trypsin activity monitoring.
• The NIR-sensitive dye-peptide conjugate leverages fluorescence ON/OFF sensing for enhanced detection.
• This innovative strategy holds potential for advancing cancer biomarker diagnostics.