Enumerating virus-like particles in an optically concentrated suspension by fluorescence correlation spectroscopy

Area of Science:

• Biophysics
• Nanotechnology
• Spectroscopy

Background:

• Fluorescence correlation spectroscopy (FCS) is a sensitive nanoparticle detection method.
• Low concentrations of biological nanoparticles, like viruses, are often below FCS detection limits.
• Optical trapping can concentrate nanoparticles, but their behavior in these fields needs study for FCS feasibility.

Purpose of the Study:

• To investigate the feasibility of using FCS for enumerating nanoparticles concentrated by optical trapping.
• To experimentally examine nanoparticle behavior within optically generated trapping potentials.
• To validate theoretical predictions of particle concentration enhancement by optical fields.

Main Methods:

• Combined optical trapping with fluorescence correlation spectroscopy (FCS).
• Used colloidal suspensions of polystyrene (PS) nanospheres and HIV-1 virus-like particles as model systems.
• Analyzed nanoparticle concentration and behavior using optical trapping energies and statistical methods.

Main Results:

• Demonstrated the combined system's ability to detect and analyze nanoparticle concentrations.
• Provided experimental data on nanoparticle behavior within optical potential wells.
• Discussed the applicability of FCS for enumerating field-enriched nanoparticles.

Conclusions:

• Optical trapping effectively enhances nanoparticle concentration for FCS detection.
• Understanding nanoparticle behavior in optical fields is crucial for accurate enumeration.
• The combined FCS and optical trapping approach shows promise for detecting low-concentration nanoparticles.