Biocompatible, adsorptive and antibacterial polysulfone hollow fibre membrane incorporated with silica alpha mangostin for uremic toxins removal

Abstract

Kidney failure patients rely on haemodialysis treatment to survive. However, unlike the kidney, this treatment cannot remove protein bound uremic toxins effectively and its long exposure to dialysis fluid poses risk of bacterial contamination. Hence, the main objective of this study is to develop a biocompatible, adsorptive and antibacterial polysulfone (PSf) based dual-layer hollow fibre (DLHF) membrane for efficient uremic toxins removal. In the first phase of the study, a silica nanoparticle with adsorption property was hybrid with a-mangostin via sol-gel technique, to enhance its biocompatibility. The synthesized nanoparticle had the Santa Barbara Amorphous-15 (SBA-15) mesoporous silica characteristic with particle size range of 15-25 nm, as confirmed by Fourier transform infrared spectroscopy (FTIR), particle size analysis, X-ray powder diffraction (XRD) and transmission electron microscopy (TEM). An adsorption study of a protein bound uremic toxin, namely p-cresol, and an antioxidant activity study were conducted, where the effect of a-mangostin addition was investigated. Silica nanoparticle showed the highest p-cresol adsorption capacity of 198 mg/g, followed by silica nanoparticles containing 5 wt% a-mangostin (186 mg/g) and 2 wt% a-mangostin (179 mg/g), respectively. Silica nanoparticle with 5 wt% a-mangostin prolonged the blood clotting time by 21.5% and inhibited the formation of reactive oxygen species by 36% compared to silica nanoparticle. The addition of 5 wt% a-mangostin enhanced the antioxidant property and maintained the good p-cresol adsorption capacity of silica nanoparticle. In the second phase of the study, 2 wt% silica and 1-2 wt% silica/a-mangostin nanoparticles were incorporated into PSf membrane, individually, where their effects on the surface properties, the adsorption capacity and the biocompatibility of the membrane were determined. Results showed that the membrane incorporated with 2 wt% silica/a-mangostin nanoparticle had a reduced water contact angle by 12.5%, indicating its improved surface hydrophilicity. Besides, the incorporation of silica/a-mangostin nanoparticle enhanced the p-cresol adsorption capacity of the membrane by 20.9% with the value of 56 mg/g. The silica/a-mangostin also improved the scavenging activity of hydrogen peroxide and nitrogen oxide by 61.8% and 36%, respectively and inhibited the formation of human complement fragment 5a (C5a) by 27.3%. In the final phase of the study, DLHF membranes consisting different combinations of inner and outer layers were prepared. 2 wt% of silica and activated carbon (AC) was incorporated in the outer layer of the membrane, individually, to impart antibacterial property to the membrane. Compared to the single layer hollow fibre membrane, the DLHF membranes showed 6-8% improvement of bovine serum albumin (BSA) rejection. DLHF membrane with the combination of silica/a-mangostin nanoparticle in the inner layer and AC in the outer layer possessed the highest removal of urea and creatinine throughout the 4-hour filtration. The silica/a-mangostin nanoparticle promoted the membrane’s interaction with urea and creatinine via chemisorption. Moreover, the AC in the outer layer of DLHF membrane successfully filtered bacteria via bacteria entrapment. The membrane displayed the highest antibacterial capability against Escherichia coli and Staphylococcus aureus, by having an antibacterial rate of 68% and 75%, respectively. The biocompatible and adsorptive DLHF membrane was successfully developed for safe and effective removal of uremic toxins in haemodialysis application.