Polymethylmethacrylate Membrane Dialyzer: Historic but Modern

Abstract

Polymethylmethacrylate (PMMA) hollow fiber membranes are one of the synthetic polymer hollow fiber membranes used to the hollow fiber artificial kidney. A PMMA hollow fiber membrane (PMMA membrane) has unique properties including the uniform structure and the adsorption property. Hemodialyzers using PMMA membranes, Filtryzer®, were approved in Japan in 1977 and have been used worldwide for over 40 years and so is a historical hemodialyzer.Various types in Filtryzer® having different pore sizes are developed and used in the clinical field. Filtryzer® B3 is a low-flux dialyzer. Filtryzer® BK has three types having different pore sizes, and above all, BK-F has the largest pores in the Filtryzer® series. Filtryzer® BG has a more uniform membrane structure by using weak anionic polymers compared with the earlier Filtryzer® series to remove β2-MG more. Filtryzer® NF is the latest Filtryzer® series and was developed as a dialyzer having improved antithrombogenicity compared with previous models and having protein adsorption property as the same with them. There have been many reports concerning Filtryzer® including improvement of patients' symptoms such as pruritus and nutrition on the advantages for dialysis patients. Although PMMA membranes are historic dialysis tools used for over 40 years, they are also modern dialysis membranes that have been updated to respond to dialysis therapy at those time.

Keywords: Adsorption; Filtryzer; Patient-reported outcomes; Polymethylmethacrylate; Polymethylmethacrylate hollow fiber membrane.

Fig. 1.

Structures of PMMA and PS membranes. a PMMA membrane. b PS membrane. Cross section images were obtained with a scanning electron microscope.

Fig. 2.

Comparison of protein removals for Filtryzer® series and PS dialyzers. a Filtryzer® BG-U. b Filtryzer® BK-F. c Filtryzer® NF-H. Protein removal was evaluated with minimodules under hemofiltration conditions. The results are presented as the mean ± standard deviation (n = 3). The values within parenthesis show molecular weight for each protein. Minimodules, whose effective surface area was 0.01 m², were made by PMMA or PS hollow fibers collected from dialyzers. Human plasma containing the evaluated proteins were prepared as the test solution and circulated through the minimodules for 1 h under hemofiltration conditions (volume of the test solution: 11 mL/min, plasma flow rates: 3.0 mL/min, ultrafiltration rates: 0.08 mL/min). Saline was added to the plasma as a substitution fluid (substitution fluid flow rates: 0.08 mL/min). The protein concentrations and volumes of test solutions were measured before and after evaluation. RRs (%) were calculated using RR (%) = 100 × (C_0h × V_0h − C_1h × V_1h)/C_0h × V_0h, where C₀ is the protein concentration in the serum before the evaluation; C_1h is the protein concentration in the serum 1 h after the beginning of the evaluation; V_0h is the serum volume before the evaluation; and V_1h is the serum volume 1 h after the beginning of the evaluation. β2-MG, β2-macroglobulin (11.8 kDa); IL-6, interleukin-6 (23 kDa); HMGB-1, high-mobility group box-1 protein (30 kDa); α1-MG, α1-microblobin (33 kDa); α1-AGP, α1-acid glycoprotein (44 kDa); MMP-3, matrix metalloproteinase-3 (45 kDa); ALB, albumin (66 kDa).

Fig. 3.

Concept and characteristics of Filtryzer® NF series. Schematic representation of Filtryzer® NF series (a, image of BG membrane; b, image of NF membrane). c Infrared spectra of albumin. Images of membrane surfaces after in vitro incubation in human blood (d, image of BG membrane; e, image of NF membrane). f Electrophoresis of proteins adsorbed on BG and NF membranes.