Fig. 3. The use of siRNA and mutant proteins to investigate nanoparticle endocytosis. (a) Micrographs of HeLa cells, which were incubated with silica-coated iron oxide nanoparticles (Fe₃O₄@SiO₂) for 4 h; on the left image control cells without siRNA treatment and on the right cells with knockdown of caveolin-1; blue = DAPI (nuclei), green = Transferrin Alexa Fluor® 488 conjugate (cytosol), red = Alexa Fluor® 555 (Fe₃O₄@SiO₂). (b) Representative images of a HeLa cell expressing green fluorescent protein (1), EH29 (mutant form of eps15) (2), and Y14F (mutant form of caveolin 1) (3) incubated with carboxylate-modified polystyrene nanoparticles in serum-containing media. Average fluorescence based on nanoparticle spot (4) and average nanoparticle spot density per cell area (5) for HeLa cells expressing green fluorescent protein, EH29, and Y14F incubated with nanoparticles in serum-containing media. Adapted with permission from (a) ref. 113 and (b)ref. 213. Copyright (a) 2016 Bohmer et al., and (b) 2012 Smith et al., licensed by Dove Medical Press Limited.