Endotoxin adsorption of various dialysis membranes: in vitro study

Endotoxin (ET) in the dialysate is known to adsorb on dialysis membranes made of polyether polymer alloy (PEPA) and polymethylmethacrylate (PMMA). In the present study, we investigated the adsorption of ET on dialysis membranes with a focus on PEPA membranes and polysulfone (PS) membranes that are extensively used in artificial kidneys or as ET-removal filters. In the case of PEPA, the compounding of polyvinylpyrrolidone (PVP) was changed, and both a hydrophobic version and a hydrophilic version were used on the blood side. For the PS dialysis, commercial membranes (APS (Asahi), BSP (Toray), PSN (Fresenius), CLPS (Terumo)) were used. Adsorption was evaluated by exposing both sides of the membrane after it had been primed with physiological saline: the ET concentration on the blood side and dialysate side of the dialysis membrane was monitored during the 240 min from the start of the exposure. When the PEPA membrane was investigated, ET was significantly adsorbed on the hydrophobic version. For PS membranes, ET was adsorbed on the blood side or on both the blood and dialysate sides, depending on the membrane. PS dialysis membranes can adsorb ET but the power and site of adsorption are different even between membranes made of the same material. In addition to electrostatic action attributable to the compounding of hydrophilic agent PVP on the dialysis membrane, the distribution of PVP that was compounded and the potential of the membrane itself are considered to cause differences in adsorption.