Data on the in vitro elution of substances from three types of polysulfone membrane dialyzers as well as a non-polysulfone cellulose triacetate membrane dialyzer evaluated using ultraviolet absorption

We evaluated the influences of the priming process (washing with saline), saline circulation conditions, and saline incubation on the in vitro elution of substances from three types of polysulfone (PSu) membrane dialyzers sterilized using gamma irradiation [NV-15X (Toray Industries, Inc.)], autoclaving [RENAK-PS1.6 (Kawasumi Laboratories, Inc.)], or in-line steam [FX-140J (Fresenius Medical Care)] methods as well as a non-PSu cellulose triacetate (CTA) membrane dialyzer [FB-150U(NIPRO)]. The effect of priming was evaluated by circulating 1000 mL of saline through the dialyzers at a rate of 100 mL/min and measuring the elution level of the substances by determining their ultraviolet (UV) absorption at 220 nm using spectrophotometry. All the tested dialyzers showed that the elution of the substances decreased as per the order of sample collection. Primed dialyzers were used in the subsequent experiments. Circulating saline through the primed membrane dialyzers at a flow rate of 100 mL/min caused time-dependent elution of substances from all the tested dialyzers; increasing the flow rate to 200 mL/min did not have a significant effect on the time-dependence or elution amount at each time point (0–8 h). The elution was also evaluated after incubating the membrane dialyzers with saline for 24 h. A co-submitted article (Sato et al., 2021) detailed the preparation of the identical experimental circuits, as well as the influences of saline washing, saline circulation conditions, and saline incubation on the elution of the hydrophilic agent polyvinylpyrrolidone (PVP) from each dialyzer using the Müller method, which can enable specific detection of PVP (Müller, 1968). The relative elution levels of PVP among the dialyzers and the experimental conditions were different from those of substances determined using UV (220 nm) absorption. Our data might be used for further development of experiments for identifying non-PVP substances eluted from dialyzers by providing information regarding the conditions of the elutions and types of dialyzers from which they are eluted.

tested dialyzers; increasing the flow rate to 200 mL/min did not have a significant effect on the time-dependence or elution amount at each time point (0-8 h). The elution was also evaluated after incubating the membrane dialyzers with saline for 24 h. A co-submitted article (Sato et al., 2021) detailed the preparation of the identical experimental circuits, as well as the influences of saline washing, saline circulation conditions, and saline incubation on the elution of the hydrophilic agent polyvinylpyrrolidone (PVP) from each dialyzer using the Müller method, which can enable specific detection of PVP (Müller, 1968). The relative elution levels of PVP among the dialyzers and the experimental conditions were different from those of substances determined using UV (220 nm) absorption. Our data might be used for further development of experiments for identifying non-PVP substances eluted from dialyzers by providing information regarding the conditions of the elutions and types of dialyzers from which they are eluted.  Table   Subject Hematology Specific subject area In vitro characterization of hemodialyzer membranes Type of data Graph Figure Table  How data were acquired The UV (220 nm) absorption of the eluates was determined using a spectrophotometer (Hitachi; U-5100). The statistical analysis was conducted with the Statcel 4 (The Publisher OMS Ltd. Japan). Data format Raw Parameters for data collection 1. The flow rates at which saline was circulated in the experimental circuits. 2. Duration of the circulation.

Description of data collection
Each dialyzer was set as per the experimental circuits described in Fig. 1A-C of the co-submitted manuscript [1] . In experiments with the circuits in Fig 1A  and B, saline was circulated in the experimental circuit at a rate of 100 mL/min or 200 mL/min and was then collected for the measurement of UV (220 nm) absorption. In experiments with the circuit in Fig. 1C

Value of the Data
• In this study, when the UV (220 nm) absorption of the eluted substances was measured, the elution patterns of the substances from the dialyzers ( Table 1 ) were distinct from those determined using the Müller method [1] , which can specifically detect PVP [2] . This fact suggests that substances other than PVP are eluted from these dialyzers. • Although PVP reportedly absorbs UV light [3] , this study provided evidence indicating that the evaluation of the PVP elution from dialyzers is not feasibly performed by measuring the UV (220 nm) absorption. This idea is in agreement with a recent report as per which, the detection of the UV absorption spectrum of the PVP is required to determine the concentration of the PVP eluted from dialyzers [4] . • Several studies have focused on PVP elution from PSu membrane dialyzers because PVP could cause adverse effects in the human body [5][6][7][8][9][10][11] . Our data provides evidence that substances other than PVP can be eluted from PSu membrane dialyzers, emphasizing the importance of identifying the eluted substances for ensuring the safety of hemodialysis patients. • Researchers and medical staff working on biomedical substances, such as dialyzer membranes, can benefit from our data. • Our data could be used for developing experiments designed to identify the additional substances eluted from dialyzers by providing information regarding the conditions of the elutions and the types of dialyzers from which they are eluted.

Data Description
Each dialyzer was set in the circuit described in Fig. 1 A of the co-submitted article [1] . Thereafter, 10 0 0 mL of saline was circulated in the experimental circuit at a flow rate of 100 mL/min and was collected from the circuit exit in 250 mL samples for measuring the UV (220 nm) absorption. The analytical samples were named as follows: S1, S2, S3, and S4, in the order of their collection. Values are presented as the mean ± standard error for the six independent experiments.  Each primed dialyzer was set in the circuit described in Fig. 1 B of the co-submitted article [1] . Each primed dialyzer was set in the circuit described in Fig. 1 C of the co-submitted article [1] and was then incubated with saline at 25 °C for 24 h without circulation. After incubation, the saline was recovered for measuring the UV (220 nm) absorption. Values are presented as mean ± standard error for the six independent experiments. ※ P < 0.05, ※※ P < 0.01. Abbrevia

Dialyzers
This study included three types of PSu membrane dialyzers and one non-PSu membrane dialyzer. The PSu membrane dialyzers were sterilized with either gamma irradiation [NV-15X (Toray  Industries,

Preparation of the experimental circuits
To test the effects of the priming process on the in vitro elution of unidentified substances from the PSu and non-PSu dialyzer membranes, the experimental circuit illustrated in Fig. 1 A of the co-published article [1] was built as following ( Fig. 4 a). Extracorporeal blood circuit containing air traps (Kawasumi Laboratories, Inc.) was first connected to either of above-mentioned dialyzers. Next, the circuit was connected to the blood pump of the dialysis machine (Toray Medical Co., Ltd.) and then saline (0.9% NaCl) containing bag (Toray Medical Co., Ltd.). Finally, the end of circuit opposite to sampling point was closed by forceps. Thereafter, we circulated 10 0 0 mL of saline in the circuit at a flow rate of 100 mL/min and collected the saline from the circuit exit in 250 mL samples to determine the contents of the unidentified substances.
To examine the effects of the circulation conditions on the in vitro elution of the unidentified substances from the dialyzer membranes, the experimental circuit illustrated in Fig. 1 B of the co-published article [1] was built as following ( Fig. 4 b). Extracorporeal blood circuit containing air traps (Kawasumi Laboratories, Inc.) was first connected to either of above-mentioned dialyzers. Next, the circuit was connected to the blood pump of the dialysis machine (Toray Medical Co., Ltd.). Finally, both ends of circuit were put in the beaker. The dialyzers in the circuit were washed by circulating 10 0 0 mL of saline throughout the circuit. Thereafter, 500 mL of fresh saline (37 °C) was poured into the beaker and circulated in the experimental circuit at a flow rate of 100 mL/min or 200 mL/min. The beaker was put in the thermostatic bath to keep the temperature of saline at 37 °C during the circulation. The analytical samples for the measurement were collected from the beaker at 0, 2, 4, 6, and 8 h after the start of the circulation.
To examine the effect of incubation of the dialyzer membranes with saline on the elution of unidentified substances from the primed dialyzers, the experimental circuit illustrated in Fig. 1 C of the co-published article [1] was built as following ( Fig. 4 c). Extracorporeal blood circuit containing air traps (Kawasumi Laboratories, Inc.) was first connected to either of above-mentioned dialyzers. Next, the circuit was connected to the blood pump of the dialysis machine (Toray Medical Co., Ltd.) and then saline (0.9% NaCl) containing bag (Toray Medical Co., Ltd.). Finally, both ends of circuit were closed by forceps. The dialyzers in the circuit were washed by circulating 10 0 0 mL of saline throughout the circuit. The circuit was then filled with saline and incubated at 25 °C for 24 h. After incubation, the saline was recovered from the circuit for measurement.

Measurement of the UV absorption of the eluates
The UV (220 nm) absorption of the eluates was determined using a spectrophotometer (Hitachi; U-5100). One ml of each analytical sample was put in quartz cell for measurement of the UV absorption.

Statistical analyze
The statistical significance was calculated using Statcel4 software (The Publisher OMS Ltd. Japan). First, the normality of the distribution was evaluated by comparing the results from the experiments using the four different dialyzers. If normal distribution was confirmed, the Tukey-Kramer method was used for multigroup analysis ( Fig. 3 ). If normal distribution was not confirmed, the multigroup analysis was performed using the Steel-Dwass method ( Figs. 1 and 2 ).

Declaration of Competing Interest
The authors declare that they have no known competing financial interests or personal relationships that have or could be perceived to have influenced the work reported in this article.