Methods
Both nitric acid digestion and enzyme digestion were tested with liver and
lung tissue as well as with cultured cells. Tissue processing with a mixture of
protease enzymes is preferred because it is applicable to a wide range of particle
compositions. Samples were visualized via fluorescence microscopy and
transmission electron microscopy to validate the SdFFF results. We describe in
detail the tissue preparation procedures and discuss method sensitivity compared
to reported levels of nanoparticles in vivo.