Preparation of poly(epsilon-lysine) adsorbents and application to selective removal of lipopolysaccharides

To remove endotoxins (lipopolysaccharides; LPS) from cell products used as drugs, water-insoluble poly(epsilon-lysine) (PL) particles were prepared by cross-linking with PL originating from Streptomyces albulus and chloromethyloxirane (CMO). The apparent pKa (pK(a,app)) and the anion-exchange capacity of the particles were easily adjusted by changing the PL ratio and the CMO ratio. The higher the pK(a,app), the greater the LPS-adsorption capacity of the particles. On the other hand, when the PL ratio (in the particles) increased to 75 unit-mol% or higher, the adsorption of bovine serum albumin by the particles also increased, but decreased with increasing ionic strength of the buffer to mu = 0.2 or higher. The adsorption of gamma-globulin increased with decreasing PL ratio to 65 unit-mol% or lower. As a result, when the PL ratio was 70 unit-mol% and the pK(a,app) was 6.7, the PL/CMO particles selectively removed LPS from various protein solutions that were naturally contaminated with LPS, at pH 6.0 and mu = 0.05.