Adsorption of Low Density Lipoproteins on an Azobenzene-Containing Polymer Brush: Modelling by Coarse-Grained Molecular Dynamics

Abstract

One of the strategies to reduce the contents of low density lipoproteins (LDLs) in blood is a hemoperfusion, when they are selectively retracted from plasma by an adsorber located outside the patient’s body. Recently, a photo-controllable smart surface was developed experimentally, that is characterized by high selectivity and reusability. It comprises a nanocarrier functionalised by a brush of azobenzene-containing polymer chains. We present a mesoscopic model that mimics principal features of this setup and focus our study on the role played by the length and flexibility of the chains and grafting density of a brush. The model for LDL comprises a spherical core covered by a shell of model phospholipids. The model is studied via coarse-grained molecular dynamics simulation, performed with the aid of the GMBOLDD package modified for the case of soft-core beads. We examined the dependencies of the binding energy on both the length of polymer chains and the grafting density of a brush and established optimal conditions for adsorption. These are explained by competition between the concentration of azobenzenes and phospholipids in the same spatial region, flexibility of polymer chains, and excluded volume effects.