[論文レビュー] Thickness effects in the electromechanical stability of charged biological membranes

Sirui Ning, Yannick A. D. Omar+2 more|arXiv (Cornell University)|Mar 24, 2026

Microbial Inactivation Methods被引用数 0

ひとこと要約

The paper develops a 2+δ dimensional theory to capture finite-thickness electrohydrodynamics and mechanics of charged lipid membranes, showing thickness-dependent Maxwell stresses dominate electrostatic renormalizations of tension and bending rigidity under physiological screening, and that surface charge can stabilize membranes.

ABSTRACT

Understanding how electric fields destabilize biological membranes is important for electroporation-based technologies and bioelectronic interfaces. However, theoretical descriptions of this phenomenon remain fragmented. Existing theories treat either electrostatics in membranes of finite thickness or electrohydrodynamic flows at idealized zero-thickness interfaces, leaving unresolved a unified description that simultaneously incorporates finite membrane thickness, surface charge, and bulk electrohydrodynamics. Here, we apply a recently-developed, dimension-reduction framework that captures the coupled electrohydrodynamic and mechanical effects governing height fluctuations of a charged lipid bilayer of thickness $δ$ in an electrolyte characterized by Debye screening length $λ$. We derive voltage- and charge-dependent renormalizations of the effective surface tension and bending rigidity, along with a dispersion relation governing undulatory instabilities. A wide range of prior theoretical results arise as limiting cases of our more general theory when finite-thickness effects are neglected or screening is asymptotically strong. The key new contribution arises from traction moments generated across the finite membrane thickness, which are absent in zero-thickness descriptions. Under physiological screening ($δ/λ\sim 4$), these contributions account for more than $>70\%$ of the total electrostatic correction to both surface tension and bending rigidity. The theory further reveals that surface charges can stabilize the membrane at physiological ionic strengths, increasing the effective tension and shifting electroporation thresholds in a manner that depends on charge asymmetry between the leaflets.

研究の動機と目的

• Motivate understanding of how electric fields destabilize or stabilize biological membranes in electroporation and bioelectronic interfaces.
• Obtain a self-consistent, thickness-aware description that couples electrostatics, hydrodynamics, and mechanics for charged bilayers.
• Derive voltage- and charge-dependent renormalizations of surface tension and bending rigidity and a dispersion relation for membrane instabilities.
• Highlight how finite-thickness traction across the bilayer alters previous zero-thickness or static models.

提案手法

• Apply the (2+δ)-dimensional framework to a finite-thickness lipid membrane with asymmetric leaflet charges.
• Reduce the 3D balance laws to a 2D surface description using Chebyshev polynomial expansions across thickness (x ≈ Σ x_k P_k(Θ)).
• Solve coupled Poisson–Nernst–Planck equations in the bulk with Maxwell stresses and interfacial boundary conditions to obtain traction t^±.
• Derive thickness-dependent Maxwell stresses inside the membrane and express the effective surface tension and bending rigidity (Λ^eff, k_b^eff) with closed-form dispersion relation ω(q).
• Obtain leading-order equations for small fluctuations using Monge representation and linearize to obtain ω(q) = - [q/(μ(4+q^2δ^2))](Λ^eff + (k_b^eff/2) q^2).
• Show how previous theories arise as limits when thickness effects are neglected or screening is strong.]
• research_questions: ["How do finite membrane thickness and dielectric mismatch modify electrostatic stresses on a charged lipid bilayer under an applied voltage?","What are the voltage- and charge-induced renormalizations of membrane surface tension and bending rigidity?","How do bulk electrohydrodynamics and interfacial traction differences across the two leaflets influence membrane stability and dispersion relations?","Under physiological screening, what is the relative importance of thickness-dependent terms in determining electromechanical instabilities?","How do leaflet charge asymmetry and ionic strength shift electroporation thresholds?"]
• key_findings:[

実験結果

主な発見

• Thickness-dependent contributions account for more than 70% of the electrostatic correction to both surface tension and bending rigidity under physiological screening (δ/λ ~ 4).
• Voltage tends to destabilize tension but, with finite thickness, can be offset by thickness corrections and leaflet charge effects.
• Surface charges can stabilize the membrane at physiological ionic strengths, increasing effective tension and shifting electroporation thresholds in a manner that depends on charge asymmetry (α).
• In the strong screening regime, surface-charge contributions raise Λ^eff and modestly raise k_b^eff; in weak screening, Λ^eff can become negative, promoting undulations.
• The theory generalizes previous static or zero-thickness models and recovers them as limits; thickness corrections enter via Q^α_;α terms representing intra-membrane traction gradients.
• For given parameters, the model predicts substantial renormalizations of mechanical moduli and altered instability onset compared to zero-thickness theories.