(698e) Molecular Simulation on the Antifouling Mechanism of Zwitterionic Materials

Zwitterionic materials are a family of materials that have moieties possessing both cationic and anionic groups. They have a special ability of resisting non-specific protein adsorption. In this work, molecular simulation is used to study the antifouling mechanism of zwitterionic polymer membranes at a molecular level. Four membranes are investigated and compared: pure polysulfone(PSF), poly(ethylene glycol) (PEG)-PSF, Sulfobetaine methacrylate(SBMA)-PSF and carboxybetaine methacrylate (CBMA)-PSF. The latter two are widely studied zwitterionic materials. Each of these membranes is placed at the base of a simulation box and brought into contact with a thin film of explicit water. The interface potential approach is used to compute wetting properties (e.g., contact angle) of water at the interface. The structure and dynamics of water near membrane surfaces is analyzed to provide information about the hydration strength of different membranes. The results show that the tetrahedral arrangement of water is interrupted severely and the motion of water is slowed down significantly near zwitterionic polymer membranes, suggesting that a strong hydration layer is formed near the surface of these membranes. Since this water layer creates a strong repulsive force on proteins, zitterionic membrane becomes antifouling. In an effort to understand the underlying mechanism of these destructuring effects and slow dynamics of water, the dynamics of hydrogen bonds are studied. It is observed that zwitterionic materials are able to form larger in number and more stable hydrogen bonds with water compared to other polymers. Further atom group analysis shows that the anionic groups in zwitterionic materials are most responsible for their strong hydrophilicity and nonfouling properties.