Effect of γ irradiation on the surface properties of wet polysulfone films containing poly(vinylpyrrolidone)

Abstract

In Japan, hemodialyzers are usually sterilized by γ irradiation. However, the polymer materials used in the dialysis membrane, such as polysulfone (PSf) and poly(vinylpyrrolidone) (PVP), undergo crosslinking or degradation on exposure to γ radiation. In the present study, we prepared PSf/PVP films (PVP content, 0-50 wt%) and used atomic force microscopy (AFM) to perform nanoscale evaluations of the effect of γ irradiation (25 and 50 kGy) on the surface properties of wet PSf/PVP surfaces. Force-curve measurements were used to evaluate the hardness of and fibrinogen adsorbability on the wet PSf/PVP surface; fibrinogen adsorbability on the wet PSf/PVP surface was evaluated using AFM probes with fibrinogen immobilized on the tips of the probes. At PVP levels greater than 5 wt%, the wet PSf/PVP film surface was completely covered with hydrated and swollen PVP particles. The surface hardness of the wet PSf/PVP films exposed to 25-kGy γ irradiation greatly decreased with increasing PVP content, whereas the surface hardness of the wet PSf/PVP films exposed to 50-kGy γ irradiation did not decrease significantly. At higher PVP levels, the reduction in the fibrinogen adsorbability on a wet PSf/PVP film exposed to 25-kGy γ irradiation was more significant than that on a wet PSf/PVP film exposed to 50-kGy γ irradiation. PVP particles on the wet PSf/PVP film surface exposed to 50-kGy γ irradiation did not show significant hydration and swelling because the polymer materials PVP-PSf and PVP-PVP in these membranes has undergone excessive crosslinking due to γ irradiation.

Poly(N-vinyl-2-pyrrolidone) elution from polysulfone dialysis membranes by varying solvent and wall shear stress

“…PSf and PVP are cross-linked when a PSf/PVP film is irradiated by gamma rays [19]. The cross-linked PSf-PVPs are effective in reducing PVP elution from the dialyzers because of high wall shear stress.…”

“…We have demonstrated that increasing the PVP content of PSf/PVP surfaces lowered the surface hardness [19]. A PSf material does not swell appreciably when it is wet and forms a hard surface.…”

Comparative Study on Elution of Polyvinylpyrrolidone on Dialyzers Using Ultraviolet Analysis and Iodine Method

“…Steam sterilization or autoclaving can result in a hydrophilic, well-biocompatible dialyzer membrane. 2,13 Gamma irradiation can lead to cross-linking of PVP 16,23 and main polymer as polysulfone, 2,5 which effectively reduce PVP elution from dialyzer membranes 1 or can destruct PVP chains. 10 The influence of the sterilization on PVP amounts eluted from dialyzers investigated here cannot be discussed further, because nonsterile references as well as details of membrane composition (PSu/ PVP, PES/PVP) and sterilization conditions are not accessible.…”

“…This led to numerous publications dealing with this topic. 1,[3][4][5][6][7][8][9] Different studies described dependence of PVP elution on methods of sterilization, 1,10,11 aging 3 as well as other conditions. 11 Others focused on investigating the biocompatibility of dialyzers with respect to sterilization 11,12 and further parameters.…”

“…3,14,15 It is known that environmental conditions for the dialyzer such as oxidative degradation as well as sterilization conditions can change PVP chain lengths. 3,10 Cross-linking can decrease the mobility of PVP, 5,16,17 whereas degradation can increase PVP elution. 10 In most cases, a potassium triiodide reagent 18,19 -sometimes called the Müller method-is used to quantify the amount of eluted PVP by PVP-iodine-complex formation in dialyzer elution studies.…”