Contamination of nanoparticles by endotoxin: evaluation of different test methods

<p>Abstract</p> <p>Background</p> <p>Nanomaterials can be contaminated with endotoxin (lipopolysaccharides, LPS) during production or handling. In this study, we searched for a convenient <it>in vitro</it> method to evaluate endotoxin contamination in nanoparticle samples. We assessed the reliability of the commonly used limulus amebocyte lysate (LAL) assay and an alternative method based on toll-like receptor (TLR) 4 reporter cells when applied with particles (TiO₂, Ag, CaCO₃ and SiO₂), or after extraction of the endotoxin as described in the ISO norm 29701.</p> <p>Results</p> <p>Our results indicate that the gel clot LAL assay is easily disturbed in the presence of nanoparticles; and that the endotoxin extraction protocol is not suitable at high particle concentrations. The chromogenic-based LAL endotoxin detection systems (chromogenic LAL assay and Endosafe-PTS), and the TLR4 reporter cells were not significantly perturbed.</p> <p>Conclusion</p> <p>We demonstrated that nanoparticles can interfere with endotoxin detection systems indicating that a convenient test method must be chosen before assessing endotoxin contamination in nanoparticle samples.</p>