While efficient removal of uremic toxins and accumulated water is pivotal for the well-being of dialysis patients, protein adsorption to the dialyzer membrane reduces the performance of a dialyzer. Hydrophilic membrane modification with polyvinylpyrrolidone (PVP) has been shown to reduce protein adsorption and to stabilize membrane permeability. In this study we compared middle molecule clearance and filtration performance of nine polysulfone-, polyethersulfone-, and cellulose-based dialyzers over time. Protein adsorption was simulated in recirculation experiments, while β2-microglobulin clearance as well as transmembrane pressure (TMP) and filtrate flow were determined over time. The results of this study showed that β2-microglobulin clearance (−7.2 mL/min/m²) and filtrate flow (−54.4 mL/min) decreased strongly during the first 30 min and slowly afterwards (−0.7 mL/min/m² and −6.8 mL/min, respectively, for the next 30 min); the TMP increase (+37.2 mmHg and +8.6 mmHg, respectively) showed comparable kinetics. Across all tested dialyzers, the dialyzer with a hydrophilic modified membrane (FX CorAL) had the highest β2-microglobulin clearance after protein fouling and the most stable filtration characteristics. In conclusion, hydrophilic membrane modification with PVP stabilizes the removal capacity of middle molecules and filtration performance over time. Such dialyzers may have benefits during hemodiafiltration treatments which aim to achieve high exchange volumes.

Performance and hemocompatibility are the main focus areas in the development of new hemofilters for continuous kidney replacement therapy. The novel multiFlux hemofilter features a polysulfone membrane with increased hydrophilicity to improve performance stability and hemocompatibility. In the present in vitro study, we compared the multiFlux hemofilter to established hemofilters on the market, i.e., Ultraflux AV (polysulfone-based), Prismaflex HF (polyarylethersulfone-based) and Prismaflex ST (AN69 ST-based). For the characterization of performance, dialysate-side plasma clearance of urea, creatinine and β2-microglobulin (β2M) were investigated over 24 h. Hemocompatibility was characterized in a blood recirculation setup by determining activation of platelets, plasmatic coagulation, the complement system and leukocytes. For urea and creatinine clearance, all hemofilters reached or approached the effluent limit across all time points. For β2M, the multiFlux hemofilter showed significantly higher clearance values at each time point vs. all comparators (p < 0.001) and the most stable performance over 24 h. The multiFlux hemofilter also showed a favorable hemocompatibility profile, especially in terms of platelet activation (vs. Ultraflux AV and Prismaflex HF) and complement activation (vs. all comparators). This in vitro study supports previous findings that increased membrane hydrophilicity improves performance stability and hemocompatibility of synthetic membranes.