Study of the insertion of a small symmetric star polymer into different phospholipid bilayers

Abstract

During the last two decades, small symmetric star polymers (SSSP) are attracting a great interest because they are being used in different biomedical applications as drug deliveries or tissue engineering, for a wide range of clinical treatments. In this context, we focused our interest on the study of the insertion of a small symmetric star polymer (SSSP) into different models of cell membranes. From our study based on MD simulations with atomic detail, we saw how the insertion of SSSP is a favorable process from a thermodynamic point of view, which is governed by the increase in the entropy of the system during their insertion process. Respect to the insertion mechanism that these SSSP molecules follow during their insertion process into a membrane, it was evidenced that they only penetrate into the membrane when one of its 3 arms orientates perpendicularly to the surface of the lipid bilayer, followed by a diminishing in the Lennard-Jones interaction energy between the SSSP and the lipid bilayer. From a detailed analysis of the surface area per phospholipid, the order parameters of the lipid hydrocarbon tails and membrane thickness of the lipid bilayers, we did not identify any structural perturbation in the membrane due to the presence of the SSSP. However, a critical perturbation in the lateral pressure profile was measured in the case of binary lipid bilayers composed of dipalmitoylphosphatidylcholine and DiPalmitoylPhosphatidylSerine in the presence of SSSP, which can have an important effect on the physiological behavior of the cell membrane.