Fluorescent nanocrystals as colloidal probes in complex fluids measured by fluorescence correlation spectroscopy

Area of Science:

• Materials Science
• Biophysics
• Nanotechnology

Background:

• Fluorescent colloidal nanocrystals (quantum dots, QDs) are valuable tools for biological imaging.
• Understanding their diffusion in complex biological fluids is crucial for accurate probing.
• Potential artifacts in fluorescence measurements need careful consideration.

Purpose of the Study:

• To characterize the diffusion of CdSe and CdSe/ZnS QDs in actin solutions.
• To determine the hydrodynamic radii of QDs in various solvents.
• To assess QDs as probes for soft biological matter and investigate measurement artifacts.

Main Methods:

• Fluorescence Correlation Spectroscopy (FCS) was employed to study QD diffusion.
• Hydrodynamic radii were measured in organic solvents and aqueous solutions.
• Numerical simulations were used to explain fluorescence-related artifacts.

Main Results:

• Apparent diffusion times and concentrations were overestimated at high excitation intensities without proper modeling.
• QD diffusion coefficients decreased with increasing actin concentration.
• An intrinsic polymer viscosity of 0.12+/-0.02 ml mg(-1) was determined for actin.

Conclusions:

• QDs can be effectively used as probes in soft biological matter like actin networks.
• Careful consideration of fluorescence properties is necessary to avoid measurement artifacts.
• The study provides insights into QD behavior in complex biological environments.