A Heptamethine Cyanine-Based Near-Infrared Optical Sensor for Copper(II) Detection in Aqueous Solutions and Living...

Area of Science:

• Biomedical Engineering
• Chemical Biology
• Analytical Chemistry

Background:

• Copper ions are vital for biological processes but toxic in excess.
• Accurate detection of copper (Cu²⁺) is crucial for understanding its role in health and disease.
• Existing detection methods may lack sensitivity, selectivity, or applicability in biological systems.

Purpose of the Study:

• To develop a novel near-infrared (NIR) optical sensor for sensitive and selective detection of Cu²⁺.
• To characterize the sensor's binding properties and performance in vitro.
• To demonstrate the sensor's utility for real-time Cu²⁺ imaging in living cells.

Main Methods:

• Synthesis of a heptamethine cyanine scaffold conjugated with a 1,10-phenanthroline Cu²⁺-binding receptor (IRPhen).
• Spectroscopic analysis (absorption, emission) to determine optical properties and binding constants.
• In vitro selectivity assays with competing metal ions.
• Cell-permeability studies and live-cell imaging using confocal microscopy in fibroblast cells.

Main Results:

• IRPhen exhibits strong NIR absorption (750 nm) and emission (808 nm).
• The sensor demonstrates high sensitivity (detection limit 0.286 µM) and selectivity for Cu²⁺.
• Rapid, reversible 1:1 binding with a binding constant of 1.3 × 10⁶ M^-1 was observed.
• IRPhen is cell-permeable and successfully detected dynamic Cu²⁺ changes in living WS1 cells.

Conclusions:

• IRPhen is a robust and effective NIR optical sensor for Cu²⁺ detection.
• The sensor's cell-permeability and real-time imaging capabilities are valuable for biological research.
• This platform can advance the study of copper homeostasis and related pathologies.
• The design principles may be adapted for developing sensors for other metal ions.