Can Martini Coarse-Grained Models Capture Anti-Biofouling Behavior of Polyelectrolyte Brush Coatings?

Biofouling has widespread implications for everyday materials, including biomedical devices, personal protective equipment, and marine coatings, leading to performance degradation and high costs. Polyelectrolyte and polyzwitterionic brush coatings are known to exhibit anti-biofouling behavior due largely to a strongly coupled hydration layer, yet the detailed mechanism is not fully understood. Moreover, only a handful of polymer chemistries have thus far been identified as highly anti-fouling.

Molecular dynamics (MD) simulations are a vital tool for studying polymer-protein interactions at angstrom-scale resolution, enabling both screening of polymer chemistries for anti-fouling properties, and interpreting experimental results indicating anti-fouling behavior. Coarse-grained (CG) simulations, in which atoms are grouped into effective interaction sites, lead to substantial gains in computational efficiency and allow for accessing microsecond timescales in large polymer systems. The Martini CG approach lends itself to modeling complex heterogenous systems, including proteins and polymers, by a modular building block strategy: a well-defined set of CG particle (bead) types classified by polarity are fit to reproduce thermodynamic partitioning data, and system-specific structural information is derived from all-atom reference simulations.

In this work we develop new Martini CG models for a series of polyelectrolyte and polyzwitterion chemistries: bonded parameters are fit to all-atom polymer simulations and a new bead type for an amine-oxide zwitterion is introduced. We use the Martini 2 refined polarizable force field, which includes polarizable water and ion models needed to accurately capture the electrodynamics of the charged polymer brushes. The CG brush models, grafted to a silica slab, are validated by comparing polymer/water density profiles and pair correlation functions against all-atom systems. Finally, adsorption energies of several common proteins are computed by a series of metadynamics simulations. We assess whether the CG Martini models can correctly rank the anti-biofouling performance of the different chemistries compared to all-atom simulations and atomic force microscopy (AFM) experiments.

Acknowledgements:
This work was supported by the U. S. Department of Energy Office of Science FWP ERKCZ64, Structure Guided Design of Materials to Optimize the Abiotic-Biotic Material Interface, as part of the Biopreparedness Research Virtual Environment (BRaVE) initiative. This work was performed at the Center for Nanophase Materials Sciences, a US Department of Energy Office of Science User Facility operated at Oak Ridge National Laboratory. This research used resources of the Oak Ridge Leadership Computing Facility (OLCF) at the Oak Ridge National Laboratory, which is supported by the Office of Science of the U.S. Department of Energy under Contract No. DE-AC05-00OR22725.