Fig. 4

NPs trafficking between different cell lines. a MP-AES assay to quantify nanoparticle distribution (gold content) between monocytes and MSCs when the PEG-HGNs were incubated simultaneously with either or with both cell types, when nanoparticles were previously incubated with MSCs, or when they were pre-incubated with monocytes. b A similar MP-AES series of experiments of gold distribution was carried out between tumoral (B16-F1) cells and monocytes. c Time-lapse images corresponding to the transfer of PEG-HGNs between MSCs (marked with blue and green dots). The frames have been selected because in both cases there were monocytes close by that did not take the passing by nanoparticles. Time-lapse videos showing these and other examples of selective transfer are available as Additional files 2 (PEG-HGNs added simultaneously) and 3 (PEG-HGNs transference among MSCs)