Effects of membrane structure on removal of low molecular weight proteins.

Much attention is being devoted to the efficient removal of beta 2-microglobulin from patients on hemodialysis as it may cause amyloidosis. The objective of the present article is to clarify the beta 2-microglobulin removal characteristics of dialysis membranes having varying water contents and pore radii. For membranes of regenerated cellulose, polymethylmethacrylate (PMMA) and ethylenevinyl alcohol (EVA), solute and pure water permeability and water content were determined by the standard methods. Data analysis using a tortuous pore model allows determination of pore radius, surface porosity, and tortuosity, and hence, the sieving coefficient as a function of Stokes radius. Based on the tortuous pore model calculation, little beta 2-microglobulin is removed from patients on hemodialysis by regenerated cellulose and PMMA membranes, but EVA membranes, with a sieving coefficient of 0.5, are capable of removing it. The solute permeability for urea is about 2 orders greater than that for beta 2-microglobulin.