Molecular Dynamics Study of Oligomer-Membrane Complexes with Biomedical Relevance

The use of liposomes as drug delivery systems (DDS) is well known. However, the stability of liposomes (shelf stability in bloodstream) for this kind of application is an issue. One way to address this problem is to develop polymer-liposome complexes to provide an improved stability as well as better selectivity characteristics. This work reports a molecular dynamics (MD) study on polymer-membrane complexes with biomedical interest. A bilayer membrane was used to mimic the liposome surface, whereas the targeted isopropylacrylamide based polymers were replaced by representative oligomers. The MD simulations were performed by using the united-atoms 53A6 GROMOS force-field, with the GROMACS 4.5.4 package in a Linux cluster. Two oligomers were tested, and their interaction with a bilayer surface was analyzed. In order to understand how the oligomer-membrane complex reacts under different thermal environments, the systems were simulated at several temperatures. It was found that the studied oligomers presented distinct effects in the bilayer. The inclusion of cholesterol at the end of isopropylacrylamide chain enabled the permeation of the oligomer and promoted the bilayer stability. On the other hand, both oligomers showed the common tendency of promoting the penetration of water molecules to the bilayer center.