This document describes the application of an assay using the LAL (Limulus Amebocyte Lysate) reagent to evaluate nanomaterials for in vitro cell culture bioassay systems. The assay is suitable for use with samples of nanomaterials dispersed in an aqueous medium, e.g. water, physiological saline or reaction medium, as well as media incubated with nanomaterials for a given time at 37 ° C. It is designed for samples intended for in vitro systems, however, the methods can also be adapted for nanomaterials being administered to animals parenterally.