Polysulfone/iron oxide nanoparticles mixed matrix membranes for hemodialysis application

Hemodialysis is a process of purifying the blood of a person whose kidneys are not working normally. The design of a hemodialysis membrane with superior uremic toxin separation and sufficient biocompatibility is of great demand. Hence, the objective of this study is to fabricate a high performance and biocompatible polysulfone/iron oxide nanoparticles (PSf/IONPs) mixed matrix membrane (MMM) for hemodialysis application. In the first phase of the study, the poor dispersion of IONPs in the polymer solution was addressed by a chemical modification using citric acid (CA) at the weight ratio of 1:5-1:25 (IONPs:CA). The dispersion of the IONPs was studied by observing the particle stability in water. PSf/IONPs MMMs comprised of 18 wt% PSf, 4.8 wt% polyvinylpyrrolidone and 0.1 wt% IONPs at various IONPs:CA weight ratios were then prepared by dry-wet spinning process. The results revealed that the optimum IONPs:CA weight ratio was 1:20, in which 49% of the IONPs was recovered after 3 days in water. As a result of the improved IONPs dispersion, the MMM exhibited good water transport features. In the second phase of the study, the effect of dope extrusion rate (DER) from 1.0 to 2.5 mL/min, and air gap from 10 to 60 cm, on the MMM morphology and liquid separation characteristics was investigated. The higher DER increased the MMM wall thickness, while the increase of air gap reduced the MMM diameter. The ideal morphology for hemodialysis membrane was obtained at the DER of 1.0 mL/min and the air gap of 50 cm. At those membrane spinning conditions, the MMM achieved pure water permeability (PWP) of 70.84 Lm-2h-1bar-1, bovine serum albumin (BSA) rejection of 98.2% and high sieving coefficient of urea (1.0) and lysozyme (0.7). In the next phase, the effect of IONPs loading (0-0.1 wt%) on the MMM physicochemical properties and separation performance were studied. The PSf/IONPs MMM possessed an improved thermal stability at higher IONPs loading. Besides, the MMM porosity and surface hydrophilicity were enhanced by increasing the IONPs loading. It was found that the MMM fabricated at 0.05 wt% IONPs loading recorded the highest PWP and BSA rejection (P= 110.47 Lm-2h-1bar-1; R= 99.9 %). Moreover, the MMM displayed the best separation performance by removing 82% urea and 46.7% lysozyme. In the final phase of the study, the membrane surface morphology was studied and the biocompatibility of the MMMs was evaluated in terms of protein adsorption, platelet adhesion, blood coagulation time and compliment activation. The PSf/IONPs MMMs possessed a smoother surface and smaller surface pore size compared to the common PSf membrane. Furthermore, the PSf/IONPs MMM demonstrated lesser protein adsorption and platelet adhesion at higher IONPs loading while keeping a normal blood coagulation time and satisfactory complement activation. The PSf/IONPs MMM showed an excellent separation performance and good biocompatibility for hemodialysis application