How the Incorporation of Pluronic Block Copolymers Modulates the Response of Lipid Membranes to Mechanical Stress

Abstract

We employ atomistic molecular dynamics simulations to investigate the effect that the incorporation of the nonionic amphiphilic copolymer known as Pluronic L64 has on the mechanical stability of a DPPC membrane. The simulations reveal that the incorporation of the polymer chains leads to membranes that can sustain increasing mechanical stresses. Analysis of mechanical, structural, and dynamic properties of the membrane shows that the polymer chains interact strongly with the lipids in the vicinity, restraining their mobility and imparting better mechanical stability to the membrane. The hybrid membranes under tension remain thicker, more ordered, and stiffer in comparison to their lipid analogues. Trans-bilayer lipid movements (flip-flop) are observed and appear to be triggered by the presence of the polymer chains. A careful analysis of the pore formation under high tensions reveals two distinctive mechanisms that depend on the distribution of the hydrophilic polymer blocks in the bilayer. Finally, the rate of growth of the formed membrane defects is slowed down in the presence of polymers. These findings show that Pluronic block copolymers could be exploited for the formation of optimized hybrid nanodevices with controlled elastic and dynamic properties.

Amphiphilic copolymers change the nature of the ordered-to-disordered phase transition of lipid membranes from discontinuous to continuous

“…In addition, we will discuss the different impact that is observed on the different membrane phases. The investigation of these systems under mechanical stress in the liquid crystalline phase, as explored in our previous work 32 revealed that the L64 Pluronic copolymers make the L α membranes stiffer, more ordered and less fluid but to our knowledge, no evidence exists on their effect on the lipid membrane gel phase.…”

“…The details of the calculation of the order parameter can be found in our previous work. 32 A mean value for S CD is computed for the sn−1 tails of 512 lipids and the final 100 ns of the simulations. At the ordered phase of the DPPC bilayer, the increased S CD denotes that the lipid tails are highly aligned in parallel to the bilayer normal.…”

<p>Ocular Inserts of Voriconazole-Loaded Proniosomal Gels: Formulation, Evaluation and Microbiological Studies</p>

“…In addition, pluronics retard the drug leakage by a suggested mechanism as they may be adsorbed on cholesterol membrane; stabilize the vesicles via discriminatory incorporation into low lipid density regions of the membrane, as a result of which, firmly packed lipids constituting the drug are formed. 42 The lower entrapment efficiency of Tw 80 in relation to Sp 60 formulations may be as a result of Tw 80 hydrophilicity with HLB value greater than that of Sp 60 (HLB =15 compared to 4.7).…”

Rational design of block copolymer self-assemblies in photodynamic therapy

“…Computer simulations enable one to model lipid bilayers and to examine how they behave in presence of polymer molecules or self-assemblies. Zaki and Carbone [169] used MD simulations to assess the effects of PEO-PPO-PEO triblock copolymers on DPPC bilayers under mechanical stress. They showed that the copolymer inserted itself in the membrane, leading to the formation of hybrid membrane with better mechanical properties.…”