PORE-SIZE CONTROLLED AND POLY(ϵ-LYSINE)-IMMOBILIZED CELLULOSE SPHERICAL PARTICLES FOR REMOVAL OF LIPOPOLYSACCHARIDES

Abstract

Poly(ϵ-lysine) was covalently immobilized onto cellulose spherical particles and used for selective adsorption of pyrogenic lipopolysaccharides (LPS) from protein solutions. The resulting poly(ϵ-lysine)-immobilized cellulose particles (PL-cellulose), which had diameters of 44 to 105 μm and matrix's pore-sizes of 2 × 103, 1 × 104, and >2 × 106 as molecular mass exclusions (Mlim), were used as adsorbents. The adsorption of LPS and protein to the adsorbent were determined using a batchwise method. The larger the pore size (Mlim) of the adsorbent, the larger is the LPS-adsorbing activity of the adsorbent. The apparent dissociation constant between the LPS (E. coli O111:B4) and the adsorbent decreased from 3.8 × 10−10 to 1.1 × 10−11 M with an increase in the Mlim from 2 × 103 to >2 × 106 at an ionic strength of μ = 0.05 and a pH of 7.0. On the other hand, the adsorbing activity of bovine serum albumin also increased with the increasing Mlim of the adsorbent, but sharply decreased with increasing ionic strength of the buffer. When PL-cellulose-103, having a small Mlim of 2 × 103, was used as the adsorbent at a wide ionic strength of μ = 0.05 to 0.4 and a pH of 7.0, it selectively reduced LPS in various protein solutions, including 1 mg mL−1 of protein and 1500 to 32,000 pg mL−1 of natural LPS. When PL-cellulose-106, having a large Mlim of over 2 × 106, was used as the adsorbent, it only selectively removed LPS at a high ionic strength of μ = 0.4 and a pH of 7.0. The LPS-removing activity of PL-cellulose-106 was always stronger than that of PL-cellulose-103. PL-cellulose-106 decreased the concentration of LPS in each protein solution to less than 10 pg mL−1. On the other hand, the recovery rate (99%) of protein for PL-cellulose-103 was higher than that for PL-cellulose-106 (96 to 97%) in all cases.