Fig. 2

Cellular uptake in vitro and biodistribution in vivo. A Confocal laser scanning microscopy (CLSM) images, B flow cytometry profiles, and C the mean fluorescence intensity, as determined from the CLSM images, of 4T1 cells incubated with MMP-2-treated or MMP-2-free PFP@PDM-PEG at various time points; scale bar: 20 μm (n = 5, t test, *p < 0.05). D In vivo fluorescence images of tumor-bearing mice at various time points postinjection and E ex vivo fluorescence images of the main organs: heart, liver, spleen, lung, kidney, and tumor (white dotted circles). F Quantitative analysis of the fluorescence intensity in the tumor sites at different time points in vivo and G quantitative analysis of the corresponding fluorescence intensities of the tissues in vitro (n = 3, t test, *p < 0.05)