Lipid Packing in Lipid-Wrapped Nanoparticles.

Area of Science:

• Computational chemistry and biophysics
• Materials science
• Nanotechnology

Background:

• Lipid-wrapped nanoparticles (LNP) are crucial in drug delivery and biomaterials.
• Understanding the self-assembly and phase behavior of LNPs is essential for their application.
• Previous studies have explored LNP structure, but a comprehensive understanding of their phase transitions remains incomplete.

Purpose of the Study:

• To investigate the equilibrium structure and phase behavior of lipid-wrapped nanoparticles (LNP).
• To determine the relationship between nanoparticle size, lipid number, and LNP configuration.
• To characterize a unique order/disorder transition in LNPs.

Main Methods:

• Hybrid molecular dynamics/Monte Carlo (MD/MC) simulations were employed.
• A three-bead lipid model was utilized to simulate a wide range of LNP sizes (R ~ 40 nm).
• Jarzynski free energy calculations were performed to validate the simulation method.

Main Results:

• The study determined average nanoparticle radius, lipid distribution in layers, and configurational information for various LNP sizes.
• A novel order/disorder transition was identified, distinct from lamellar bilayers.
• This transition was found to be weak and continuous for small lipid numbers, sharpening to first-order for N > 10000.

Conclusions:

• The nanoparticle core influences the inner lipid layer, while curvature introduces disorder.
• The number of lipids in the inner and outer layers can be accurately predicted based on nanoparticle radius.
• The findings provide critical insights into LNP self-assembly and stability, informing future design for applications.