Targeting nanoplatform synergistic glutathione depletion-enhanced chemodynamic, microwave dynamic, and selective-microwave thermal to treat lung cancer bone metastasis

Abstract

Once bone metastasis occurs in lung cancer, the efficiency of treatment can be greatly reduced. Current mainstream treatments are focused on inhibiting cancer cell growth and preventing bone destruction. Microwave ablation (MWA) has been used to treat bone tumors. However, MWA may damage the surrounding normal tissues. Therefore, it could be beneficial to develop a nanocarrier combined with microwave to treat bone metastasis. Herein, a microwave-responsive nanoplatform (MgFe₂O₄@ZOL) was constructed. MgFe₂O₄@ZOL NPs release the cargos of Fe³⁺, Mg²⁺ and zoledronic acid (ZOL) in the acidic tumor microenvironment (TME). Fe³⁺ can deplete intracellular glutathione (GSH) and catalyze H₂O₂ to generate •OH, resulting in chemodynamic therapy (CDT). In addition, the microwave can significantly enhance the production of reactive oxygen species (ROS), thereby enabling the effective implementation of microwave dynamic therapy (MDT). Moreover, Mg²⁺ and ZOL promote osteoblast differentiation. In addition, MgFe₂O₄@ZOL NPs could target and selectively heat tumor tissue and enhance the effect of microwave thermal therapy (MTT). Both in vitro and in vivo experiments revealed that synergistic targeting, GSH depletion-enhanced CDT, MDT, and selective MTT exhibited significant antitumor efficacy and bone repair. This multimodal combination therapy provides a promising strategy for the treatment of bone metastasis in lung cancer patients.

Keywords: Chemodynamic therapy; MgFe2O4@ZOL nanoparticles; Microwave dynamic therapy; Microwave thermal therapy; Targeting.

Graphical abstract

Fig. 1

Schematic illustration of the microwave and MgFe₂O₄@ZOL NPs used in synergistic tumor therapy. (A) The synthesis process of MgFe₂O₄@ZOL NPs. (B) Schematic diagram of synergistic therapy involving targeting, CDT, MDT, and selective-MTT, and bone repair for bone metastasis.

Fig. 2

Synthesis and characterization of MgFe₂O₄ and MgFe₂O₄@ZOL NPs. (A) XRD pattern; (B) N₂ absorption/desorption isotherms; (C) pore size distribution curves; (D) SEM image; (E) TEM image; (F) TEM element mapping; (G) FTIR spectra; (H) XPS survey; (I) high-resolution XPS spectra of N1s; (J) TG analysis curves; (K) DLS; (L) Zeta potential.

Fig. 3

In vitro microwave heating effect of MgFe₂O₄ and release of MgFe₂O₄@ZOL. (A) The principle of microwave heating. (B) FLIR images of concentration gradients of MgFe₂O₄ NPs when the suspension was exposed to MW irradiation. (C) Temperature variations of MgFe₂O₄ NPs suspension at different concentrations when the solution was exposed to MW at 5 W for 5 min. (D) Changes in the temperature of the MgFe₂O₄ NPs suspension (1 mg/mL) at different microwave power. (E) Infrared thermal images of MgFe₂O₄ NPs irradiated by microwave at different power levels. (F) Microwave thermal stability of MgFe₂O₄ NPs (2.5 mg/mL) under MW irradiation (5 W) for 5 on-off cycles. (G) The UV–vis spectra of ZOL, MgFe₂O₄, NH₂-PEG-NH₂, and MgFe₂O₄@ZOL. (H) The release curves of MgFe₂O₄@ZOL NPs at various acid environments. (I) The in vitro bone affinity of MgFe₂O₄ and MgFe₂O₄@ZOL NPs.

Fig. 4

Oxidation-reduction reactions of nanomaterials. (A) Generation of singlet oxygen after treatment with different concentrations of MgFe₂O₄ NPs (0, 200, 500, 1000, 2000 μg/mL) and irradiation of MW. (B) The relative GSH content in cancer cells after treatment with various concentrations of MgFe₂O₄ or MgFe₂O₄@ZOL NPs (0, 12.5, 25, 50, 100, and 200 μg/mL). (C and D) UV–vis absorbance of MB treated with a gradient of concentrations of MgFe₂O₄ NPs or acidic environment (insert: images of MB solutions; the concentrations separately are 0, 200, 500, 1000, and 2000 μg/mL; PH are 4.5, 5.5, 6.5, and 7.4). (E) EPR detection of MgFe₂O₄ under MW irradiation to produce ·OH. (F) The quantity of cellular ROS produced after different treatments. (G) Fluorescence images illustrating ROS in cells.

Fig. 5

The proliferation and viability of the tumor cells. (A) The cell proliferation of A549 cells treated with MgFe₂O₄ NPs for 1, 3, and 5 days. (B) The effects of MgFe₂O₄ NPs and MgFe₂O₄@ZOL NPs on A549 cell proliferation for 24 h. (C) Effects of MgFe₂O₄ NPs combined with MW irradiation on A549 cell proliferation. (D) The live/dead A549 cells staining with Calcein-AM/PI.

Fig. 6

In vitro anticancer effects. (A) TEM was used to detect the treatment of A549 cells: (A-1) Blank control; (A-2) MgFe₂O₄ NPs; (A-3) MgFe₂O₄@ZOL NPs; (A-4) MW control; (A-5) MW + MgFe₂O₄, and (A-6) MW + MgFe₂O₄@ZOL. (Red arrow indicates the cell nucleus, blue arrow indicates the endoplasmic reticulum, black arrow indicates the mitochondria, green arrow indicates the nanoparticles, and purple arrow indicates the lipid droplets.) (B) The diagram of cancer cell apoptosis process. (C) Fow cytometry was conducted to show the apoptosis of A549 cells in different treatment groups. (D) The apoptosis rate in different groups.

Fig. 7

Biological interactions between MgFe₂O₄@ZOL NPs and A549 cells in vitro. The A549 cells were treated with blank control, MgFe₂O₄, MgFe₂O₄@ZOL, MW + control, MW + MgFe₂O₄, and MW + MgFe₂O₄@ZOL. (A and D) Colony formation and clone formation rate. (B and E) Images of the transwell assay and invasion ability of A549. (C and F) Cell scratch assay and migration capability.

Fig. 8

Effects of MgFe₂O₄ and MgFe₂O₄@ZOL on the differentiation of osteoblasts in vitro. (A, B, and C) ALP activity of C3H10 cells on days 3, 7, and 14: (A) Macroscopic images; (B) Microscopic images; (C) Quantitative analysis of ALP activity. (D, E, and F) Alizarin red staining of C3H10 cells on days 3, 7, and 14: (D) Macroscopic images; (E) Microscopic images; (F) Quantitative analysis of mineralized nodules.

Fig. 9

In vivo antitumor effects. (A) Images of microwave heating in vivo. (B) Nude mice with tumor at the end of the experiment. (C) Images of tumors excised from mice. (D) Temperature changes caused by microwave heating in vivo. (E) Weight gain in various groups of mice. (F) The increase in tumor volume in mice between groups. (F) The tumor slices were stained with Prussian blue. (G) The tumor slices were stained with Prussian blue (PB) (the arrow points to the dyed Fe³⁺). (H–J) H&E, TUNEL, and KI67 staining of tumor tissue between groups: (H) H&E staining; (I) TUNEL staining; (J) Ki67 staining.