Electromechanical limits of polymersomes

Area of Science:

• Materials Science
• Biophysics
• Polymer Science

Background:

• Amphiphilic diblock copolymers self-assemble into polymersomes, mimicking lipid bilayers.
• Understanding membrane cohesiveness is crucial for applications in drug delivery and biomaterials.

Purpose of the Study:

• To compare the electromechanical properties and breakdown behavior of diblock copolymer membranes with lipid membranes.
• To investigate the influence of hydrophobic thickness on membrane capacitance and breakdown potential.
• To analyze the mechanical response and dynamics of polymersomes post-electroporation.

Main Methods:

• Fabrication of polymersomes and liposomes with varying hydrophobic thicknesses (d = 3-15 nm).
• Electromechanical breakdown measurements to determine breakdown potential (V(c)).
• Capacitance measurements to assess membrane dielectric properties.
• Analysis of post-poration dynamics to evaluate membrane viscosity.

Main Results:

• Polymersomes (d = 15 nm) exhibited a breakdown potential of 9 V, significantly higher than liposomes (d = 3 nm) at 1 V.
• Electromechanical stress at breakdown followed a universal V(c)(2) dependence for both membrane types.
• Membrane capacitance strongly correlated with hydrophobic thickness (d), consistent with thermodynamic models.
• Diblock copolymer membranes displayed viscous behavior during post-electroporation recovery.

Conclusions:

• Diblock copolymer membranes offer tunable mechanical properties and enhanced robustness compared to lipid membranes.
• Simple thermodynamic models effectively describe the capacitance and breakdown behavior of these synthetic membranes.
• The inherent viscosity of polymersomes influences their response to electrical stress and recovery dynamics.