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… (More)
Figure 2 Overview of the different LAL assays when performed in the presence of particles (12.5, 50 and 200 μg/ml or 0.2, 2 and 20 mg/ml) after spiking. A: Gel clot LAL assay; B: Endpoint chromogenic LAL assay; C: Endosafe-Portable Test System (PTS); D: Endpoint chromogenic after endotoxin extraction (shaken 10 min and centrifugation). Samples spiked with endotoxin concentrations half of assay sensitivity (½λ: 0.0625 EU/ml), assay sensitivity (λ: 0.125 EU/ml) and double of assay sensitivity (2λ: 0.25 EU/ml) (gel clot LAL assay); half of maximum of assay range (½λmax: 0.5 EU/ml) (endpoint chromogenic LAL assay); the endosafe-PTS contains an internal spiking control. Results are shown in a heat plot: Red: no clot (Gel Clot) or no spike recovery (chromogenic assays); Yellow: increased turbidity (Gel Clot); Green: clot formation (Gel Clot) or complete spike recovery (chromogenic assays). Percentages indicate percentage spike recovery. In case of the endosafePTS, measurements of Ag, CaCO3 and SiO2 samples were not performed at the lower particle concentrations (12.5 and 50 μg/ml), because the highest concentration (200 μg/ml) showed a complete spike recovery.