Recombinant Factor C (rFC) Assay
rFC is an endotoxin sensitive synthetic protein that is cloned from factor C DNA to use as an alternative in vitro LAL test 47,63-67 . In the rFC test, the binding of endotoxin activates the synthetic rFC molecule, which then cleaves a fluorescein substrate (amino-methylcoumarin), resulting in the generation of a fluorogenic compound. The fluorescence is measured twice, first at time zero and then after the endotoxin has been introduced using excitation/emission of 380/440 nm. The difference in fluorescence is proportional to endotoxin concentrations in the sample and is used to calculate a final endotoxin result. rFC is specific to endotoxin detection eliminating the dependence on nonspecific glycan binding like that in an LAL assay avoiding false positive results.68 The enzymatic sensitivity range to endotoxin is 0.05-500 EU/ml.63