Figure 4.

(A) Illustration of MM@HMFe@BS for self-amplified chemodynamic therapy and tumor metastasis inhibition via tumor microenvironment remodeling under the monitoring of MRI. (B) Representative TEM images of MM@HMFe@BS. (C) Nitrogen adsorption−desorption curve of the HMFe. Inset shows the pore size of HMFe. (D) Time-dependent decomposition behavior of MM@ HMFe@BS. (E) In vitro release profiles of BS from MM@HMFe@BS at various pH values (5.0, 6.5, or 7.4) with or without H₂O₂. (F) UV−Vis absorption spectra of TMB after coincubation with DW (deionized water), solid Fe₃O₄, and HMFe in the presence of H₂O₂ (100 μM) at pH 5.0. (G) ESR spectra of detected •OH at different conditions. (H) Western blot analysis of α4 and VCAM-1 in macrophage membrane and 4T1 cells membrane, respectively. Fluorescence images of (I) BCECF-stained and (J) APF-stained 4T1 cells treated with free BS, HMFe, HMFe@BS, and MM@HMFe@BS for 12 h. (K) Relative tumor volume changes in 4T1 tumor-bearing mice with different treatments (n = 5). (L) Lung metastasis inhibition ratios on the 15th day post-treated with different formulations in contrast to control group (n = 5). (M) Linear plot of 1/T₂ as a function of HMFe concentration. The inset is T₂-weighted MRI images of HMFe. (N) In vivo MRI of 4T1 tumor-bearing mice before and after intravenous injection of MM@HMFe@BS. Reprinted with permission from Ref. [99]. Copyright 2022, American Chemical Society. * p < 0.05.