Particle size distribution in DMPC vesicles solutions undergoing different sonication times

Area of Science:

• Lipid nanoparticle characterization
• Materials science
• Physical chemistry

Background:

• Dimyristoylphosphatidylcholine (DMPC) liposomes are crucial in drug delivery and biomembrane research.
• Understanding liposome size distribution is vital for controlling their properties and performance.
• Sonication is a common method for liposome preparation, but its effect on size distribution requires detailed investigation.

Purpose of the Study:

• To investigate the size distribution of dimyristoylphosphatidylcholine (DMPC) liposome suspensions.
• To determine the influence of sonication time on DMPC liposome size and morphology.
• To compare different data analysis methods for dynamic light scattering (DLS) in characterizing liposomes.

Main Methods:

• Dynamic Light Scattering (DLS) at a single angle was employed.
• Cumulant expansion (second- and third-order) and Regularized Laplace Inversion (CONTIN) were used for data analysis.
• Liposomes were modeled as thin-walled hollow spheres for number-weighted radius determination.

Main Results:

• Intensity-weighted mean hydrodynamic radius (r(I)) was lengthscale-dependent for both analysis methods.
• Number-weighted mean hydrodynamic radius (r(N)) obtained via CONTIN was lengthscale-independent.
• Increasing sonication time reduced vesicle size and asymmetry, leading to a plateau in number-weighted radius, standard deviation, and peak radius (r(N)(peak)).

Conclusions:

• CONTIN analysis provides a reliable lengthscale-independent number-weighted radius for DMPC liposomes.
• Sonication beyond 1 hour yields unilamellar vesicles consistent with thermodynamic predictions.
• Discrepancies at lower sonication times suggest the presence of larger, non-spherical, and floppy vesicles.