Elevation in surface enhanced fluorescence performance mediated by glutathione protonation in acidic environments

Area of Science:

• Nanotechnology
• Biomedical Engineering
• Materials Science

Background:

• Surface-enhanced fluorescence (SEF) is crucial for sensitive detection and cellular imaging.
• High concentrations of noble metal nanoparticles (e.g., silver) can cause cytotoxicity, limiting their application.
• Reducing nanoparticle concentration often leads to diminished SEF performance.

Purpose of the Study:

• To synthesize and characterize silver-carbon (Ag@C) core-shell nanoparticles for improved SEF.
• To investigate methods for restoring SEF performance at reduced nanoparticle concentrations.
• To elucidate the mechanism behind SEF enhancement using modified nanoparticles.

Main Methods:

• Synthesis of Ag@C nanoparticles with varying heating times.
• Characterization of SEF enhancement factor (EFsef) for different nanoparticle formulations.
• Surface modification of Ag@C nanoparticles with glutathione (GSH) to form Ag@C-GSH (ACG) nanoparticles.
• Evaluation of ACG nanoparticle performance across a range of pH conditions.

Main Results:

• Ag@C nanoparticles heated for 4 hours (AC4.0) exhibited the highest initial SEF enhancement.
• Dilution of AC4.0 significantly decreased EFsef.
• Surface modification with GSH (ACG) and specific pH conditions (pH 4 for ACG, pH 8 for diluted AC4.0) restored and improved EFsef at low concentrations.
• The recovery mechanism involves acid-induced protonation of GSH, mediating ACG aggregation via hydrogen bonding, thereby amplifying electric fields at hot spots.

Conclusions:

• Ag@C nanoparticles offer a platform for SEF applications.
• Glutathione modification and controlled pH are effective strategies to enhance SEF at low, non-cytotoxic nanoparticle concentrations.
• The findings provide a mechanism for boosting SEF through nanoparticle aggregation and electric field amplification, paving the way for more sensitive biosensing and imaging.