Biocompatibility enhancement of hemodialysis membranes using a novel zwitterionic copolymer: Experimental, in situ synchrotron imaging, molecular docking, and clinical inflammatory biomarkers investigations

Abstract

The aim of the current research study is to conduct a comparative assessment of biocompatibility of zwitterionic-coated polyether sulfone (PES) clinical hemodialysis (HD) membranes using both theoretical and experimental methods. Fibrinogen plays a key role in assessing membrane hemocompatibility since its membrane-surface adsorption triggers several biological reactions, complete thrombosis and embolism. As a result, adsorption of fibrinogen on the untreated PES surface and novel synthesized PES coated with poly 3-((3-(3-carboxy-2,5-dimethyltridecanamido) propyl) dimethylammonio) propane-1-sulfonate as a zwitterion (ZW) was compared. Specifically, the comparison was conducted using in situ synchrotron based micro computed tomography imaging (SR-μCT), Attenuated Total Reflection Fourier Transform Infrared (ATR-FTIR) spectroscopy, and Scanning Electron Microscopy (SEM). The in situ SR-μCT showed that fibrinogen adsorption and membrane fouling were intense on PES membrane surface. However, there was insignificant fouling in the middle layer of zwitterion coated PES membrane (PES-ZW). Moderate shifting of peaks was observed in ATR-FTIR spectra of the adsorbed fibrinogen when compared to the bulk protein spectra, which may be due to the conformational transformations occurring during the adsorption process. The spectral features indicate that PES-ZW surface has a lower adsorption affinity for fibrinogen than that for the PES surface. In this innovative study, the use of molecular modeling docking to evaluate the interaction of fibrinogen active pose with PES-ZW and PES models with the aim of gaining an in depth understanding of the functional group responsible for the interactions was explored. The PES and PES/zwitterion hemodialysis membrane models indicated minimum binding energies with fibrinogen by -6.00 and -6.70 kcal/mol, respectively. Docking studies thus suggest that the membrane's sulfone functional groups play an essential key role during the fibrinogen interaction and adsorption. The HD patients' uremic samples were incubated in vitro with PES and PES-ZW membranes for the inflammatory biomarkers released of Serpin/Antithrombin-III, Properdin, C5a, IL-1α, IL-1β, TNF-α, and IL6. This study's results emphasize that even though a neutral charge of synthesized novel zwitterion PES, which enhances biocompatibility, the sulfone group still significantly affected the interactions with fibrinogen.

Keywords: Fibrinogen; Hemodialysis membrane; Inflammatory biomarkers; Molecular modeling docking; SR-μCT; Zwitterion.