Preparation of Endotoxin-Free EquipmentSoak glassware and stir bars (for dialysis) overnight in a 1% solution of alkaline detergent (E-TOXA-CLEAN, Sigma E9029). 2. Rinse all glassware 8 to 10 times with warm running tap water, 5 times with distilled water, and finally twice with endotoxin-free water (Hyclone, SH30529.
Endotoxin testing (LAL test) ensures that sterile pharmaceutical products are safe for human use. Endotoxins are bacterial structural components that are released when such a cell is lysed. These components are toxic if administered to humans and/or animals, causing a pyrogenic response (rise in body temperature).
Endotoxin is measured in endotoxin units per milliliter (EU/mL). One EU equals approximately 0.1 to 0.2 ng endotoxin/mL of solution. Currently there are three forms of the LAL assay, each with different sensitivities.
Endotoxin refers to a component of the outer cell membrane of Gram-negative bacteria called lipopolysaccharide (LPS). The common way to detect endotoxin in water is the Limulus Amebocyte Lysate (LAL) test (2). Well-maintained and operated water systems should not see endotoxin detected regularly.
Basic Knowledge of Lipopolysaccharide (LPS)Bacteria-derived LPS, the “Immuno Vitamin”, is found abundantly in edible plants, such as grains, vegetables, and seaweed. Bacteria reside in the soil, where they help plants grow by converting nitrogen and phosphorus into forms accessible to the plants.
The most significant endotoxin is expressed by Gram-negative bacteria, which can be destroyed by a number of methods. First, endotoxins are dangerous when entering the blood, causing fever and a wide range of other possible effects including aseptic shock and death.
Five Easy Ways to Keep Your Cell Cultures Endotoxin-Free
- Use high-purity water.
- Consider choosing premium FBS.
- Check that media and additives have been tested for endotoxins.
- Follow the correct autoclaving procedures for glassware.
- Use certified plasticware.
- Reference.
Traditional Endotoxin Detection MethodsTraditionally, the in vitro LAL assay and the in vivo RPT have been used to detect and quantify endotoxin in pharmaceutical products. The LAL test has occasionally also been used to screen cerebrospinal fluid for presence of gram negative organisms associated with meningitis.
Lipopolysaccharides (LPS), also known as endotoxins, are large molecules consisting of a lipid and a polysaccharide composed of O-antigen, outer core and inner core joined by a covalent bond; they are found in the outer membrane of Gram-negative bacteria.
Being sterile means being free from microorganisms and being pyrogen-free means being free from fever-causing substances. The difference can be likened to insects and their eggs.
Although the term "endotoxin" is occasionally used to refer to any cell-associated bacterial toxin, in bacteriology it is properly reserved to refer to the lipopolysaccharide complex associated with the outer membrane of Gram-negative pathogens such as Escherichia coli, Salmonella, Shigella, Pseudomonas, Neisseria,
Examples of the bacteria by which the LPS or endotoxins are triggered are Salmonella typhi, E. coli, Vibrio cholera, Shigella, while Bacillus cereus, Bacillus anthracis, Staphylococcus aureus, Streptococcus pyrogens are examples for triggering exotoxins.
The lower the dose, the higher the limit per unit dose. Think about it this way: If the dose is 1 mg/kg/hr, the endotoxin limit is (5 EU/kg/hr) ÷ (1 mg/kg/hr) = 5 EU/mg. If the dose is 10 mg/kg/hr, the endotoxin limit is (5 EU/kg/hr) ÷ (10 mg/kg/hr) = 0.5 EU/mg.
Endotoxin is bad for you as it may cause an acute airways inflammation, manifested by subjective and clinical findings. The effects are worse among those with an existing airways inflammation induced by chemical agents, infection, or tobacco smoke.
HOW DOES ENDOTOXIN GET INTO THE BLOODSTREAM? Plasma endotoxin may be derived from bacteria in an infected local tissue, the blood, the GI or respiratory tract, or food or other ingested matter.
Endotoxin, or more accurately termed bacterial lipopolysaccharide (LPS), is recognized as the most potent microbial mediator implicated in the pathogenesis of sepsis and septic shock.
Exotoxins are usually heat labile proteins secreted by certain species of bacteria which diffuse into the surrounding medium. Endotoxins are heat stable lipopolysaccharide-protein complexes which form structural components of cell wall of Gram Negative Bacteria and liberated only on cell lysis or death of bacteria.
Conclusions: This study demonstrates that endotoxin has no direct vasodilatory effect on human skeletal muscle arterioles, but it is the release of an endothelial factor from the upstream conduit vessels that produces the loss of tone in the microvasculature.
A pyrogen is a molecule that is fever-producing. Endotoxins are found in the cell wall of Gram-negative bacteria and exotoxins are molecules that some bacteria make internally and secrete to the outside. Endotoxins and exotoxins are released when a bacterium lyses. Endotoxins come in lipopolysaccharide (LPS) form.
The toxicity of LPS is mainly due to this lipid A, while the polysaccharides are less toxic. In Gram-negative bacteria, LPS is anchored to the outer membrane via lipid A. Bacteria release LPS fragments in their environment, while this layer is constantly renewed to maintain its integrity.
Endotoxins are not secreted but are released only when the cells are disrupted, they are less potent and less specific than the exotoxins and do not form toxoids. If produced in large quantities they cause hemorrhagic shock and severe diarrhea.
Bacteria do not grow and multiply the same way as animals or humans. They take in nutrients and reproduce by dividing – one bacteria splits and becomes two bacteria, two become four, four become eight and so on. Doubling can occur quickly if the conditions – enough nutrients, proper temperature, adequate moisture, etc.
