Molecular Simulation Studies of Protein Interactions with Zwitterionic Phosphorylcholine Self-Assembled Monolayers in the Presence of Water

Abstract

Molecular simulations were performed to study the interactions between a protein (lysozyme, LYZ) and phosphorylcholine-terminated self-assembled monolayers (PC-SAMs) in the presence of explicit water molecules and ions. The results show that the water molecules above the PC-SAM surface create a strong repulsive force on the protein as it approaches the surface. The structural and dynamic properties of the water molecules above the PC-SAM surface were analyzed to provide information regarding the role of hydration in surface resistance to protein adsorption. It can be seen from residence time dynamics that the water molecules immediately above the PC-SAM surface are significantly slowed down as compared to bulk water, suggesting that the PC-SAM surface generates a tightly bound, structured water layer around its head groups. Moreover, the orientational distribution and reorientational dynamics of the interfacial water molecules near the PC-SAM surface were found to have the ionic solvation nature of the PC head groups. These properties were also compared to those obtained previously for an oligo(ethylene glycol) (OEG) SAM system and bulk water.

Molecular dynamics simulations for microscopic behavior of water molecules in the vicinity of zwitterionic self-assembled monolayers

“…In the first hydration layer, the correlation function for PC SAM decreases to nearly 0.2 after 5 ps. This is more drastic reduction, as compared with the previous report for PC SAM, 9 where it is only reduced to about 0.8 at the equivalent time. This remarkable difference results from the fact that a protein molecule is located at the separation distance of 5 Å above a PC SAM surface in the previous report.…”

“…Considering the definition of C(t), its slower decrease means that a material surface tends to bind water molecules more strongly. Besides the residence time, the orientations of the water molecules in the vicinity of a surface were evaluated by the angle y between its dipole vector and the surface normal vector, 9 as illustrated in Figure 2b. In the case of a bulk water model, molecules are randomly oriented, because all dipole angles are equally possible, resulting in the flat orientation distribution.…”

“…[8][9][10][11] Chen et al 8 reported the strong resistance of zwitterionic phosphorylcholine (PC) self-assembled monolayers (SAMs) to protein adsorption. He et al 9 also investigated the antifouling properties of PC SAMs by MD simulations. They suggested that their strong resistance to biofouling results from their capacity for hydration via electrostatic interactions.…”

“…These previous studies 8,9 are significant for the elucidation of mechanisms on the development of zwitterionic PC materials, but at the same time, a new interest arises in microscopic behaviors of water molecules in the vicinity of various types of material, including zwitterionic and nonionic ones. In this work, MD simulations are conducted to investigate the dynamics and structural properties of explicit water molecules near three types of zwitterionic SAM surface, PC, carboxybetaine (CB) and sulfobetaine (SB), as well as poly(vinyl alcohol) (PVA) and graphite surfaces.…”

Controlled loop and graft formations of water-soluble polymers on SAMs for the design of biomaterials surfaces

“…1 Much effort has been devoted to the development of polymers to eliminate protein adsorption and the subsequent cellular responses on surfaces contacting blood or body fluid in a living body. 2,3 In particular, hydrophilic polymers such as poly(ethylene glycol) (PEG) [4][5][6][7][8] and phospholipid polymers [9][10][11][12][13] have been well developed and are some of the most promising candidates to eliminate protein adsorption. They have a suitable chain length and density, excluded volume effect, entropic repulsive force, surface wettability and hydration.…”