Endotoxins are degradation products from dying gram-negative bacteria and complex aggregates of acidic lipopolysaccharides (LPS). They are composed of a lipophilic lipids part and hydrophilic polysaccharides. In humans, endotoxins can cause immune responses like fever (pyrogenic threshold is approx. 0.1 ng/kg bodyweight). Unlike bacteria themselves, endotoxins are extremely heat and pH-stable and therefore withstand sterilization.
During protein purification, the reduction of endotoxins is one of the most important and difficult steps. This often includes complex purification strategies (e.g. chromatography steps) with more or less satisfactory results. In general, the removal of contaminants in downstream processing becomes more costly the later in the process a contamination is removed. PURAFIX® ET-R depth filter sheets are the new solution for endotoxin removal earlier in the process.