Fig. 2

Au@Ag nanoparticles suppress metastasis in vivo. To test the in vivo activity of AgNP, AuNP and Au@Ag nanoparticles, 4T1 cells were transplanted into the mammary fat pad of Balb/c mice, then animals were divided into 4 groups (n = 6/group). Animals received nanoparticles peritumourally four times, and tumour sizes were repeatedly measured throughout the experimental period. Au@Ag nanoparticle treatments resulted in a significant suppression of 4T1 tumour growth (a). To investigate the anti-metastatic activities of Au@Ag nanoparticles, lower number of 4T1 cells were inoculated into the mammary fat pads of Balb/c mice then animals were divided into 5 groups (n = 6–7/group) to receive Au@Ag nanoparticles alone or in combination with doxorubicin. We found that Au@Ag alone and also in combination with doxorubicin hampered tumour progression significantly (b). After the last treatment (on day 12), animals were left untreated for further two weeks to let the metastatic lesions in the lungs grow to a potentially detectable level. On day 28 animals were euthanised and lungs were dissected. Au@Ag treatments alone and in combination with doxorubicin reduced the mass of metastatic tissue in the lung of the animals (c). Histopathology of the lung specimen also confirmed the anti-metastatic efficiency of Au@Ag, since the area of the metastatic lesions was significantly lower in nanoparticle-treated mice (c–e). *P ≤ 0.05; **P ≤ 0.01; ***P ≤ 0.001 indicates statistical significance (unpaired t-test)