Influence of Dipole Orientation of Zwitterionic Materials on Hemodialysis Membrane Interactions with Human Serum Proteins

Abstract

Hemodialysis is a lifesaving treatment for end-stage renal disease (ESRD) that exploits semipermeable membranes to remove fluids and uremic toxins from ESRD patients. Polyethersulfone (PES) is the most common membrane that is currently used in Canadian hospitals and represents 93% of the market. Nevertheless, PES membranes have limited hemocompatibility, which triggers blood activation cascades, as the rate of morbidity and mortality in ESRD patients is still unacceptably high. Surface modification with zwitterionic (ZW) materials, which are well known for their strong dipole–dipole interactions and exceptional antifouling properties, has recently received increased attention in improving PES characteristics like roughness, wettability, and biocompatibility, which are crucial factors in dialysis efficiency. The hydration structures, dynamics, and interactions of ZWs are significantly dependent on the backbone structures, such as differences in carbon space length [CSL], conformation, functional groups, pendant groups, and charge distributions, and even minor changes in ZW structure can drastically alter their behavior. However, a systematic investigation of the impact of dipole orientation of ZW on the hemocompatibility of the membranes has not yet been investigated. This study offers a comprehensive exploration of the interactions between hemodialysis membranes and human serum proteins, emphasizing the pivotal role of the zwitterion dipole orientation. We utilize molecular docking techniques to predict protein–ligand interactions, offering insights into the binding sites and binding energy of these complexes. The effect of dipole orientation on the hemocompatibility of various ZW-modified PES membranes compared to the pristine PES has been investigated using 2-methacryloyloxyethyl phosphorylcholine (MPC), 2-((2-(methacryloyloxy)ethyl)dimethylammonio)ethyl methyl phosphate (MMP), and butyl (2-((2-(methacryloyloxy)ethyl)dimethylammonio)ethyl) phosphate (MBP) zwitterions with opposite dipole orientations. Results showed that the protein–ligand interactions and affinity energies displayed by the reverse dipole moment structures are remarkably different. It was demonstrated that the MBP–PES ligand had the lowest affinity energy to interact with all examined human serum proteins compared to the structure, which had an opposite dipole moment. As a result, this membrane surface has better antifouling properties and, thus, higher hemocompatibility, which directly correlates with greater efficiency of hemodialysis in patients.