Fig. 33. In vivo anticancer activities: (a) tumor growth curves of 4T1 tumor-bearing BALB/C mice after intravenous injection with (1) PBS, (2) free MTX (MTX), (3) MTX loaded in traditional LDH nanoparticles (LDH-MTX), and (4) MTX loaded in PEG-modified ultrathin LDH nanosheets (LDH-Co-PEG MTX) (n = 5, error bar indicates standard deviation; the arrow indicates tail vein injection at day 1; * indicates p < 0.05 with Student's t test). (b) The body weight evolution of 4T1 tumor-bearing mice at different times after intravenous injection of different materials (n = 5, error bar indicates standard deviation). (c) H&E staining images of tumors slices. The tumor-bearing mice were treated with MTX, LDH-MTX, and LDH-Co-PEG MTX at day 1 and sacrificed at day 7. Higher cancer cell damage (red area indicates area of cell damage) was found in LDH MTX- and LDH-Co-PEG MTX-treated groups. Scale bar: 100 μm. Reproduced with permission from ref. 150. Copyright 2017 The American Chemistry Society.