Nonsolvent-induced phase separation preparation of porous TOPO-mixed polyethersulfone membranes for selective clearance of p-cresol from simulated serum

Uremic toxin p-cresol will accumulate in the blood when the kidney function declines, causing an increased risk of cardiovascular diseases and the mortality of the patient with end-stage rental disease. The incomplete removal of p-cresol even by a high-flux hemodialysis is mainly because most of p-cresol is bound to albumin. The efficient removal of such a toxin by a promising way is highly desired. In this study, porous polyethersulfone (PES) membranes were prepared by nonsolvent-induced phase separation, to which an additive polyvinylpyrrolidone (PVP) and a solvating extractant tri-n-octylphosphine oxide (TOPO) were added. These membranes were applied to selectively remove p-cresol from simulated serum containing comparatively large amounts of other small toxins like urea and creatinine. Morphological and physicochemical properties of the prepared TOPO-mixed membranes were examined. The adsorption isotherms of p-cresol measured at 37 °C and pH 7.4 on the prepared membranes were better described by the Langmuir equation, in contrast to the Freundlich equation. Under the ranges studied, a maximum adsorption capacity of 1.77 mmol/g for p-cresol was obtained. Cross-flow adsorption of a mixture of urea, creatinine, and p-cresol (initially, 2300, 150, and 50 mg/L, respectively) in a total reflux mode revealed that 46% of p-cresol, 1.0% of urea, and 1.1% of creatinine were removed after 4 h of operation (membrane area 42 cm², flow rate 0.2 L/min, and volume 0.5 L). This highlighted the high selectivity of p-cresol clearance over two other toxins using the prepared TOPO-mixed membranes. The hemolysis tests and time-course measurements of the cellular viability of fibroblast NIH/3T3 and leukemic THP1 cells demonstrated that the prepared TOPO-mixed membranes were hemo- and bio-compatible; therefore, they were promising and potential for future applications.