Activation of the complement system may occur during blood‐membrane interactions in hemodialysis and contribute to chronic inflammation of patients with end‐stage renal disease. Hydrophilic modification with polyvinylpyrrolidone (PVP) has been suggested to increase the biocompatibility profile of dialysis membranes. In the present study we compared the complement activation of synthetic and cellulose‐based membranes, including the polysulfone membrane with α‐tocopherol‐stabilized PVP‐enriched inner surface of the novel FX CorAL dialyzer, and linked the results to their physical characteristics. Eight synthetic and cellulose‐based dialyzers (FX CorAL, FX CorDiax [Fresenius Medical Care]; Polyflux, THERANOVA [Baxter]; ELISIO, SUREFLUX [Nipro]; xevonta [B. Braun]; FDX [Nikkisio Medical]) were investigated in the present study. Complement activation (C3a, C5a, and sC5b‐9) was evaluated in a 3 hours ex vivo recirculation model with human blood. Albumin sieving coefficients were determined over a 4 hours ex vivo recirculation model with human plasma as a surrogate of secondary membrane formation. Zeta potential was measured as an indicator for the surface charge of the membranes. The FX CorAL dialyzer induced the lowest activation of the three complement factors (C3a: −39.4%; C5a: −57.5%; and sC5b‐9: −58.9% compared to the reference). Highest complement activation was found for the cellulose‐based SUREFLUX (C3a: +154.0%) and the FDX (C5a: +335.0% and sC5b‐9: +287.9%) dialyzers. Moreover, the FX CorAL dialyzer had the nearest‐to‐neutral zeta potential (−2.38 mV) and the lowest albumin sieving coefficient decrease over time. Albumin sieving coefficient decrease was associated with complement activation by the investigated dialyzers. Our present results indicate that the surface modification implemented in the FX CorAL dialyzer reduces the secondary membrane formation and improves the biocompatibility profile. Further clinical studies are needed to investigate whether these observations will result in a lower inflammatory burden of hemodialysis patients.

Introduction: Hydrophilic modification with polyvinylpyrrolidone (PVP) increases the biocompatibility profile of synthetic dialysis membranes. However, PVP may be eluted into the patient's blood, which has been discussed as a possible cause for adverse reactions rarely occurring with synthetic membranes. We investigated the content of PVP and its elution from the blood-side surface from commercially available dialyzers, including the novel FX CorAL, with PVP-enriched and α-tocopherol-stabilized membrane, and link the results to the level of platelet loss during dialysis as a maker of biocompatibility. Methods: Six synthetic, PVP containing, dialyzers (FX CorAL, FX CorDiax [Fresenius Medical Care]; Polyflux, THERANOVA [Baxter]; ELISIO [Nipro]; xevonta [B. Braun]) were investigated in the present study. The content of PVP on blood-side surface was determined with X-ray photoelectron spectroscopy (XPS). The amount of elutable PVP was measured photometrically after 5 h recirculation. The level of platelet loss was evaluated in an ex vivo recirculation model with human blood. Findings: Highest PVP content on the blood-side surface was found for the polysulfone-based FX CorAL (26.3%), while the polyethersulfone-based THERANOVA (15.6%) had the lowest PVP content. Elution of PVP was highest for the autoclave steam-sterilized THERANOVA (9.1 mg/1.6 m 2 dialyzer) and Polyflux (9.0 mg/1.6 m 2 dialyzer), while the lowest PVP elution was found for the INLINE steam sterilized FX CorAL and FX CorDiax (<0.5 mg/1.6 m 2 dialyzer, for both). Highest platelet loss was found for xevonta (+164.4% compared to the reference) and the lowest for the FX CorAL (À225.2%) among the polysulfone-based dialyzers; among the polyethersulfone-based dialyzers, THERANOVA (+95.5%) had the highest and ELISIO (À52.1%) the lowest platelet loss. Discussion: Polyvinylpyrrolidone content and elution differ between commercially available dialyzers and were found to be linked to the membrane material and sterilization method. The amount of non-eluted PVP on the blood-side surface may be an important determinant for the biocompatibility of dialyzers.

Background: Toxin removal capacity (i.e., performance) of a dialyzer is not constant but diminishes during treatment, as the adsorption of proteins to the membrane provides an additional barrier to uremic solutes. We investigated timeresolving molecular weight retention changes among synthetic high-flux dialyzers and compared the results with recent data from a randomized controlled trial. Methods:In plasma recirculation experiments over 240 min, sieving coefficients (SC) for β2microglobulin, myoglobin, and albumin were determined for the FX CorAL (Fresenius Medical Care), ELISIO (Nipro), and xevonta (B. Braun).Molecular weight retention (MWR) curves were generated and the shifts over 120 min were characterized. Effective pore radius was determined, and the predicted albumin loss was compared with clinical data.Results: SC decreased over time for all dialyzers (mean relative decrease across all dialyzers: β2-microglobulin: 8.0% (120 min); myoglobin: 56.6% (240 min); albumin: 94.1% (240 min)). FX CorAL (7.3%, 52.6% and 91.1%) and ELISIO (7.7%, 51.0%, and 93.8%) showed a lower decrease than xevonta (9.0%, 66.2%, and 97.4%).For all dialyzers, MWR curves shifted toward lower molecular weight, with the lowest shift for FX CorAL (by 0.23 nm at SC50%, 120 min) and highest for xevonta (0.50 nm). FX CorAL had the highest slope over time and the smallest decrease in the effective pore radius (2 min: 2.31 nm, 120 min: 2.08 nm). Predicted albumin loss over 4 h was highest for xevonta (609.3 mg) and comparable between ELISIO (283.6 mg) and FX CorAL (313.3 mg).Conclusions: Substantial differences in the temporal performance profile of dialyzers exist. The present approach allows the characterization of dialyzer permeability changes over time using standard, clinically relevant protein markers.

Background and Aims Activation of the complement system may occur during blood-membrane interactions in hemodialysis and contribute to chronic inflammation of patients with end-stage renal disease (ESRD). Hydrophilic modification with polyvinylpyrrolidone (PVP) has been suggested to increase the biocompatibility profile of dialysis membranes. In the present study we compared complement activation of synthetic and cellulose-based membranes, including the polysulfone membrane with α-tocopherol-stabilized, PVP-enriched inner surface of the novel FX CorAL dialyzer, and linked the results to their physical characteristics. Method Eight synthetic and cellulose-based dialyzers (FX CorAL, FX CorDiax [Fresenius Medical Care]; Polyflux, THERANOVA [Baxter]; ELISIO, SUREFLUX [Nipro]; xevonta [B. Braun]; FDX [Nikkisio Medical]) were investigated in the present study. Complement activation (C3a, C5a, sC5b-9) was evaluated in a 3h ex vivo recirculation model with human blood. Albumin sieving coefficients were determined over a 4h ex vivo recirculation model with human plasma as a surrogate of secondary membrane formation. Zeta potential was measured as an indicator for the surface charge of the membranes. Results The FX CorAL dialyzer induced the lowest activation of the three complement factors (C3a: -39.4%; C5a: -57.5%; sC5b-9: -58.9% compared to the reference). Highest complement activation was found for the cellulose-based SUREFLUX (C3a: +154.0%) and the FDX (C5a: +335.0%; sC5b-9: +287.9%) dialyzers. Moreover, the FX CorAL dialyzer had the nearest-to-neutral zeta potential (-2.38 mV) and the lowest albumin sieving coefficient decrease over time. Albumin sieving coefficient decrease was associated with complement activation by the investigated dialyzers. Conclusion Our present results indicate that the surface modification implemented in the FX CorAL dialyzer reduces secondary membrane formation and improves the biocompatibility profile. Further clinical studies are needed to investigate whether these observations will result in a lower inflammatory burden of hemodialysis patients.

Background and Aims Hydrophilic modification with polyvinylpyrrolidone (PVP) increases the biocompatibility profile of synthetic dialysis membranes. However, PVP may be eluted into patient’s blood, which has been discussed as a possible cause for adverse reactions rarely occurring with synthetic membranes. We now investigated the content of PVP and its elution from the blood-side surface from commercially available dialyzers, including the novel FX CorAL with α-tocopherol-stabilized, PVP-enriched membrane, and link the results to the level of platelet loss during dialysis as a maker of biocompatibility. Method Six synthetic, PVP containing, dialyzers (FX CorAL, FX CorDiax [Fresenius Medical Care]; Polyflux, THERANOVA [Baxter]; ELISIO [Nipro]; xevonta [B. Braun]) were investigated in the present study. The content of PVP on blood-side surface was determined with X-ray photoelectron spectroscopy (XPS). The amount of elutable PVP was measured photometrically after 5h recirculation. The level of platelet loss was evaluated in an ex vivo recirculation model with human blood. Results Highest PVP content on the blood-side surface was found for the polysulfone-based FX CorAL (26.3%), while the polyethersulfone-based THERANOVA (15.6%) had the lowest PVP content. Elution of PVP was highest for the autoclave steam sterilized THERANOVA (9.1 mg/1.6m² dialyzer) and Polyflux (9.0 mg/1.6m² dialyzer), while the lowest PVP elution was found for the INLINE steam sterilized FX CorAL and FX CorDiax (&lt; 0.5 mg/1.6m² dialyzer, for both). Highest platelet loss was found for xevonta (+164.4% compared to the reference) and the lowest for the FX CorAL (-225.2%) among the polysulfone-based dialyzers; among the polyethersulfone-based dialyzers, THERANOVA (+95.5%) had the highest and ELISIO (-52.1%) the lowest platelet loss. Conclusion PVP content and elution differs between commercially available dialyzers and was found to be linked to the membrane material and sterilization method. The amount of non-eluted PVP on the blood-side surface may be an important determinant for the hemocompatibility of dialyzers.