Heterogeneous Kinetics in the Functionalization of Single Plasmonic Nanoparticles

Area of Science:

• Nanotechnology
• Biophysics
• Materials Science

Background:

• Ensemble measurements of DNA-functionalized gold nanoparticles in solution obscure particle-to-particle differences.
• Understanding single-particle behavior is crucial for optimizing nanoparticle applications.

Purpose of the Study:

• To investigate the functionalization of gold nanorods with thiolated single-stranded DNA (ssDNA) at the single-particle level.
• To quantify particle-to-particle variations in ssDNA coverage and binding kinetics.
• To identify the sources of heterogeneity in nanoparticle biofunctionalization.

Main Methods:

• Utilized single-particle spectroscopy to monitor gold nanorod functionalization in real time.
• Exploited the sensitivity of plasmon resonance to local refractive index changes.
• Analyzed particle-to-particle variations in plasmon shift, ssDNA coverage, and binding rates.

Main Results:

• Observed significant particle-to-particle variations in plasmon shifts, attributed to size distribution and ssDNA coverage.
• Quantified ssDNA coverage variations of approximately 10%, exceeding Poisson statistics.
• Discovered binding rates varying by an order of magnitude between particles under identical conditions.

Conclusions:

• Identified heterogeneity in ssDNA binding kinetics, likely due to variations in effective surface charge and activation energies.
• Highlighted the importance of considering kinetic heterogeneity in the application of functional nanoparticles.
• Demonstrated a versatile methodology for optimizing nanoparticle functionalization protocols.