Fluorophore-gold nanoparticle complex for sensitive optical biosensing and imaging.

Area of Science:

• Nanotechnology
• Biophotonics
• Analytical Chemistry

Background:

• Fluorophores are crucial signal mediators in biosensing and bioimaging.
• Fluorescence enhancement improves sensitivity for early disease detection.
• Metal nanoparticles, like gold nanoparticles (GNPs), generate surface plasmon fields that can modulate fluorophore emission.

Purpose of the Study:

• To theoretically analyze the effects of various parameters on fluorescence enhancement by GNPs.
• To experimentally develop an enhanced near-infrared (NIR) contrast agent using GNPs and a fluorophore.
• To determine the optimal GNP size and spacer length for maximal fluorescence enhancement.

Main Methods:

• Theoretical analysis of GNP parameters (size, shape) and fluorophore properties (distance, quantum yield) on fluorescence.
• Experimental development of a contrast agent by conjugating a fluorophore (ICG-based) to GNPs via biocompatible spacers.
• Systematic study of GNP size (3.7-16.4 nm) and spacer length (3.2-4.6 nm) effects on fluorescence intensity.

Main Results:

• Theoretical analysis guided the experimental design for fluorescence enhancement.
• A 3.9 nm spacer with a 16.4 nm GNP resulted in a 360% increase in fluorescence compared to the control.
• Experimental findings qualitatively agreed with theoretical predictions.

Conclusions:

• Theoretical modeling provides a valuable guide for optimizing fluorescence enhancement using GNPs.
• Tailoring the distance between fluorophores and GNPs via spacers significantly improves fluorescence intensity.
• This approach offers a pathway to enhance the sensitivity of existing fluorescent contrast agents for diagnostics.