Properties of binding of Escherichia coli endotoxin to various matrices

Binding of Escherichia coli O127:B8 endotoxin to a variety of resins and column materials was investigated by measuring the beta-hydroxy myristic acid content (a major component of the lipid A moiety) of endotoxin after hydrolysis by selected ion-monitoring gas chromatography-mass spectrometry. More than 80% of the endotoxin was bound to hydroxylapatite, polystyrene, Dowex 1-X2, and charcoal. The binding of endotoxin to these materials was markedly reduced by the addition of normal or delipidated serum. Phenyl- and octyl-Sepharose bound 56 and 50% of the endotoxin from saline solutions, respectively. Their percent binding was increased significantly in 1 M ammonium sulfate solutions, indicating hydrophobic interactions between endotoxin and phenyl- and octyl-Sepharose. Only 5% of the endotoxin was bound to plastic polymer PSI-HAP-100 beads, and no binding was observed with concanavalin A- and heparin-Sepharose. Study of the in vitro binding of endotoxin to the above material in the presence of serum suggests that the use of these materials in removing circulating endotoxin in vivo is limited.