Fig. 2

CD-NPs were more easily endocytosed into cells and inhibited cell proliferation. A The state of CD adsorbed cells was observed under a microscope after treating with 300 µg/mL CD-MPs and CD-NPs for 24 h. Red arrows point to CD particles adhering to cells. B The endocytosis, morphology of cells was observed by TEM after treating with 300 µg/mL mixed CD-MPs and CD-NPs for 24 h in vitro and with 32 μg mixed CD/day for 2 weeks in vivo. Red arrows point to endocytosed CD particles. C The cell proliferation was detected by CCK-8 assay. Data were expressed as the mean ± SD, n = 3. *P < 0.05, **P < 0.01 and ***P < 0.001. CD-MPs coal dust micron particles, CD-NPs coal dust nanoparticles, CD coal dust, TEM transmission electron microscope