Figure 3From: Contamination of nanoparticles by endotoxin: evaluation of different test methods Optical density by increasing concentrations of TiO 2 particles in the endpoint chromogenic LAL assay. Open symbols show optical density (OD405nm) of TiO2 particles, while closed symbols show the OD of spiked TiO2 particles. The dotted line shows the corrected OD after spiking: OD(spiked particles) – OD(particles).Back to article page