USP <85> Endotoxin Testing for Research Peptides

Endotoxin is not a live bacterial count

Endotoxins are components of Gram-negative bacterial cell walls. Contaminated water or processing surfaces are possible sources. Residues can remain after bacteria are no longer viable, which is why a no-growth result does not answer the endotoxin question. FDA: bacterial endotoxins.

Why we test for it

Why it matters for research: even very low levels of endotoxin can activate immune cells such as macrophages in cell-based experiments. That response can look like an effect of the peptide itself, so an unmeasured endotoxin level can quietly undermine a result. These are general properties of endotoxin, not findings in Morris Peppy products, and a low measured value is not an approval for human use. FDA: pyrogen and endotoxin testing.

Read activity units, not milligrams or colonies

Why interference controls matter

A sample can suppress or enhance the assay response. Recovery controls assess whether the method works in that sample. Without a valid procedure, a low value can be misleading. Ask for the actual method, sample basis, limit and any suitability qualifications.

The chapter number identifies the approach

USP <85> covers established bacterial endotoxin testing methods; USP <86> addresses recombinant-reagent approaches. The report should identify which method was actually used rather than simply using “endotoxin tested” as a badge. USP: microbiological testing standards.

Neither test is a universal screen for every immune-stimulating contaminant. Read it alongside separate microbial and sterility findings and the report for the exact lot.