Figure 2
From: Contamination of nanoparticles by endotoxin: evaluation of different test methods
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 endosafe-PTS, 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.