title: Contamination of nanoparticles by endotoxin: evaluation of different test methods.
abstract: BACKGROUND
  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 (TiO(2), Ag, CaCO(3) and SiO(2)), or after extraction of the endotoxin as described in the ISO norm 29701.
  
  
  RESULTS
  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.
  
  
  CONCLUSIONS
  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.
authors.affiliation: Laboratory of Pneumology, Unit for Lung Toxicology, KU Leuven, Leuven, Belgium.
authors.forename: Stijn
authors.initials: S
authors.lastname: Smulders
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: Kaiser
authors.forename: Stefano
authors.initials: S
authors.lastname: Zuin
authors.forename: Kirsten L
authors.initials: KL
authors.lastname: Van Landuyt
authors.forename: Luana
authors.initials: L
authors.lastname: Golanski
authors.forename: Jeroen
authors.initials: J
authors.lastname: Vanoirbeek
authors.forename: Peter
authors.initials: P
authors.lastname: Wick
authors.forename: Peter Hm
authors.initials: PH
authors.lastname: Hoet
mesh_terms: D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D017930:Genes, Reporter; D006801:Humans; D008033:Limulus Test / Q000379:methods*; D008070:Lipopolysaccharides / Q000032:analysis*; D008855:Microscopy, Electron, Scanning; D046529:Microscopy, Electron, Transmission; D053758:Nanoparticles / Q000737:chemistry*; D036103:Nanotechnology; D010316:Particle Size; D013053:Spectrophotometry; D013499:Surface Properties; D051197:Toll-Like Receptor 4 / Q000235:genetics / Q000378:metabolism
chemical_list: D008070:Lipopolysaccharides; C495345:TLR4 protein, human; D051197:Toll-Like Receptor 4; C440499:lipopolysaccharide, Escherichia coli O111 B4