Understanding the Mechanical Properties of Ultradeformable Liposomes Using Molecular Dynamics Simulations.

Area of Science:

• Biophysics
• Materials Science
• Computational Chemistry

Background:

• Improving drug delivery to solid tumors is a key challenge in cancer therapy.
• Soft, elastic liposomes show enhanced cancer cell and tumor uptake compared to rigid particles.
• Understanding liposome elasticity modulation by molecular composition is essential for therapeutic applications.

Purpose of the Study:

• To investigate how molecular structure and composition influence liposome elasticity.
• To simulate lipid bilayers by mixing long-tailed unsaturated phospholipids with short-tailed saturated lipids.
• To correlate simulation results with experimental measurements of liposome mechanics.

Main Methods:

• Performed all-atom and coarse-grained classical molecular dynamics (MD) simulations.
• Simulated lipid bilayers composed of 1,2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) or 1,2-dipalmitoleoyl-sn-glycero-3-phosphocholine (DPMPC) mixed with shorter lipids (DHPC, DDPC, DLPC, DMPC).
• Analyzed area compressibility modulus, area per lipid, interfacial structure, and lipid tail disorder.

Main Results:

• Liposomes with 25-35 mol% DHPC or DDPC mixed with DOPC or DPMPC exhibited ~10% lower area compressibility moduli, indicating reduced rigidity.
• These mixed systems showed altered lipid packing, including lower area per lipid and increased tail disorder, compared to pure bilayers or mixtures with longer saturated lipids.
• Simulation findings aligned with experimental data on stretching modulus and lysis tension, confirming the hypothesis on elasticity enhancement.

Conclusions:

• Mixing specific short-tailed lipids (DHPC, DDPC) with long-tailed phospholipids (DOPC, DPMPC) effectively reduces liposome rigidity and increases elasticity.
• Altered lipid packing and increased tail disorder are key mechanisms underlying the enhanced elasticity of these mixed liposomes.
• This study provides a molecular-level understanding of liposome elasticity, guiding the design of advanced drug delivery systems for cancer therapy.