Plier Ligands for Trapping Neurotransmitters into Complexes for Sensitive Analysis by SERS Spectroscopy

Area of Science:

• Analytical Chemistry
• Biomarker Detection
• Nanotechnology

Background:

• Catecholamines (dopamine, noradrenaline, adrenaline) are key biomarkers for neuroendocrine tumors and neurodegenerative diseases.
• Surface-enhanced Raman spectroscopy (SERS) offers multiplexing capabilities but struggles with weak signals from some analytes on robust substrates.
• Developing stable SERS substrates is crucial for accurate analyte detection.

Purpose of the Study:

• To develop a novel indicator system for enhanced SERS detection of catecholamines.
• To create a stable SERS sensor using mixed ligand complexes for improved analyte trapping and signal amplification.
• To enable sensitive quantification of dopamine using a new analytical methodology.

Main Methods:

• Synthesis of four bispidine-based bis-azole ligands with varying functional groups.
• Formation of mixed ligand complexes with Cu(II) ions and catecholamines to shift absorbance to the visible range.
• Utilized Molecular Immobilization and Resonant Raman Amplification by Complex-Loaded Enhancers (MIRRACLE) on a silver-based SERS substrate.

Main Results:

• Stable catecholamine-Cu(II) complexes were formed, exhibiting absorbance bands at 570-600 nm.
• The new absorbance band matched the LSPR of nanoparticles, enabling intense Raman signal amplification.
• Achieved sensitive determination of dopamine within a concentration range of 3.2 × 10^-12 M to 1 × 10^-8 M.

Conclusions:

• The novel indicator system effectively traps and stabilizes catecholamine-Cu(II) complexes on SERS sensors.
• The MIRRACLE methodology combined with plier-like ligands significantly enhances SERS detection sensitivity.
• This approach provides a robust platform for the sensitive detection of important neurotransmitter biomarkers.