Polymeric γ-Cyclodextrin Adsorbent for Selective Removal of Endotoxin from DNA Solution

Endotoxin (lipopolysaccharide, LPS) can be removed from a protein solution by adsorption onto cationic polymer particles. We found that LPS was selectively adsorbed on batchwise synthesized poly(epsilon-lysine)-immobilized cellulose beads (pore size: 2 x 10(3) molecular mass exclusion) from a protein (albumin or globulin) solution at a neutral pH and an ionic strength of mu = 0.2-0.4. To remove LPS from a DNA solution, copolymer particles were prepared by suspension copolymerization of gamma-cyclodextrin (CyD) and 1,6-hexamethylenediisocyanate. The LPS-removal activity of the copolymer particles was compared with that of the cationic polymer adsorbent. When DNA was present in solution with LPS under physiological conditions, LPS-removal activity of the cationic adsorbent was unsatisfactory because both the DNA and the LPS adsorb onto the each adsorbent. In contrast, the copolymer particles with the gamma-CyD cavity (CyD content: 20 mol %) could selectively remove LPS from a DNA solution (50 ug/mL, pH 6.0 and ionic strength t = 0.05-0.4) containing LPS (15/EU mL), without adsorption of DNA.