Light-Scattering Sizing of Single Submicron Particles by High-Sensitivity Flow Cytometry

Area of Science:

• Optical physics
• Nanotechnology
• Analytical chemistry

Background:

• Accurate submicron particle size measurement is vital for quality control, biomedical research, environmental studies, and drug delivery.
• Direct elastic light scattering is simple but challenged by instrument sensitivity and complex scattering-particle size relationships.
• High-sensitivity flow cytometry (HSFCM) offers superior sensitivity for nanoparticle detection.

Purpose of the Study:

• To comprehensively compare experimentally measured and Mie theory calculated light scattering intensities from single submicron particles.
• To validate a novel method for precise submicron particle size measurement using HSFCM and Mie theory.
• To assess the potential of this method for applications like bacterial sizing.

Main Methods:

• Synthesis of 38 highly monodisperse silica spheres (180-880 nm) for calibration and comparison.
• Utilizing a laboratory-built high-sensitivity flow cytometer (HSFCM) for side scattering (SSC) detection.
• Comparing experimental scattering data with Mie theory calculations for various particle types and laser polarizations.

Main Results:

• Excellent agreement was found between experimental measurements and Mie theory predictions for silica spheres and polystyrene beads.
• Parallel polarization demonstrated superior resolution of differently sized particles compared to perpendicular polarization.
• A linear correlation between measured and calculated scattering intensities was established, enabling Mie theory-based sizing.
• The developed method achieved sizing resolution and accuracy comparable to electron microscopy for Staphylococcus aureus.

Conclusions:

• The study successfully validates Mie theory for submicron particle sizing using HSFCM, offering high precision and accuracy.
• Parallel polarization enhances the ability to differentiate particle sizes.
• This method provides a robust alternative to traditional calibration curves, improving submicron particle characterization.
• The approach shows significant potential for accurate size measurement in diverse scientific and industrial applications.