Endotoxin rejection by ultrafiltration through high-flux, hollow fiber filters

The efficacy of endotoxin (ET) rejection of four hollow fiber membranes with comparable sieving properties was evaluated in an ultrafiltration experiment. The solution conditioned with type I lipopolysaccharide (LPS) from Escherichia coli, 80,000 endotoxin units (EU)/L, was filtered through polyesterpolymer alloy (PEPA), polymethyl methacrylate (PMMA), polyacrylonitrile (PAN), and polysulfone (PS) membranes. The ET activity of the filtrate was not detectable in PEPA and PMMA, 6.4 +/- .04 (mean +/- SD) EU/L in PAN, and 10.3 +/- 1.1 EU/L in PS. The ET activity of the filtrate of type II LPS from Acinetobacter solution, 80,000 EU/L, was not detectable in PEPA, 3.7 +/- 0.4 EU/L in PMMA, 16.5 +/- 1.5 EU/L in PAN, and 20.7 +/- 1.4 EU/L in the PS filter. The order of the rejection capability coincided with the adsorptive capacity as shown by the decrement in ET levels of solutions filled within the filter modules in the adsorption equilibrium experiment. In conclusion complete rejection of ET molecules can be achieved by ultrafiltration through hydrophobic membranes having a high adsorptive capacity in addition to an appropriate sieving property for ET molecules.