Open Access Research

Contamination of nanoparticles by endotoxin: evaluation of different test methods

Stijn Smulders1, Jean-Pierre Kaiser2, Stefano Zuin3, Kirsten L Van Landuyt4, Luana Golanski5, Jeroen Vanoirbeek1, Peter Wick2 and Peter HM Hoet1*

Author Affiliations

1 Laboratory of Pneumology, Unit for Lung Toxicology, KU Leuven, Leuven, Belgium

2 Empa, Swiss Federal Laboratories for Materials Science and Technology, Laboratory for Materials-Biology Interactions, St. Gallen, CH-9014, Switzerland

3 Venice Research Consortium, c/o VEGA Park - Venice Gateway for Science and Technology, Venice, Italy

4 KU Leuven BIOMAT, Department of Oral Health Sciences, KU Leuven, Leuven, Belgium

5 CEA-Grenoble, Liten, Laboratory of Tracer Technologies, Grenoble, France

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Particle and Fibre Toxicology 2012, 9:41  doi:10.1186/1743-8977-9-41

Published: 9 November 2012



Nanomaterials can be contaminated with endotoxin (lipopolysaccharides, LPS) during production or handling. In this study, we searched for a convenient in vitro 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.


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.


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.

Endotoxin; Nanoparticles; LAL assay; TLR4 reporter cells