ABSTRACT
If ever a material seemed ill suited for use in analytical assays, it is endotoxin. As a standard, it has been domesticated, but not entirely tamed, captured from the wild, grown in captivity on rich media, chemically groomed (by solvent extraction), and trained to behave in a somewhat civilized manner in modern assays. But, still, it prances like a caged lion, back and forth, unable to escape its dual amphiphilic nature-unable to decide on the direction it should go in aqueous solution. The hydrophobic end would much rather aggregate with ends of its own kind, or stick to the plastic or glass of a test tube or container in which it resides (or parenteral closure to which it has been applied for depyrogenation validation), rather than mingle with water. Furthermore, the biological activity of endogenous endotoxin derived from different bacteria runs the gamut from apyrogenic to highly pyrogenic (the extremes in variability hold true for endotoxicity also). Indeed, laboratories
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select different endotoxins for different purposes (i.e., product testing standards vs. depyrogenation validation applications) given varying empirical recovery experiences. This chapter seeks to provide an overview for endotoxin as both a parenteral contaminant and as a standard used in modern assays.
