Resolving liposomal inhibition of quantitative LAL methods

Bacterial endotoxin is composed of Lipid A as well as variable polysaccharide regions, and is capable of eliciting a pyrogenic response in vivo (1). NeXstar has developed a quantitative LAL assay at maximum sensitivity to provide assurance that its products are well below the endotoxin pyrogenic threshold. This test uses rigorous treatment of 1.0 mL liposome samples with sodium dodecyl sulfate, an anionic surfactant, or CHAPS, a zwitterionic surfactant to disrupt the lipids present in the liposome sample including endotoxin. This liposome disruption allows potentially undetectable endotoxin to become available to the LAL cascade for quantification and overcomes inhibition of the LAL test by liposomes.