Considerable future research will be needed to fully realize the potential of our
technique for nanoparticle characterization in toxicology studies. Specifically, improvements are needed to reduce particle losses during the enzyme digestion and particle recovery steps of the tissue processing, to make the method sufficiently reproducible, and to permit precise quantification of the nanoparticle burden per weight of original tissue. This paper describes experiments done with relatively high concentrations of the particles because our goal was to demonstrate proofof-concept. The limit of detection for 70 nm SiO2 particles was 25 μg of particles per SdFFF analysis sample using a light scattering detector. This particle concentration in tissue is within the range reported by in vitro and in vivo nanoparticle toxicity studies. For example, a study of fine and nanoscale quartz particles reported statistically significant responses with an intratracheal instillation dose of 1 mg/kg which equated to an initial burden of about 140 μg of particles per lung [26].