Photothermal exposure of polydopamine-coated branched Au-Ag nanoparticles induces cell cycle arrest, apoptosis, and autophagy in human bladder cancer cells

Purpose: Polydopamine-coated branched Au-Ag nanoparticles (Au-Ag@PDA NPs) exhibit good structural stability, biocompatibility, and photothermal performance, along with potential anticancer efficacy. Here, we investigated the cytotoxicity of Au-Ag@PDA NPs against human bladder cancer cells (T24 cells) in vitro and in vivo, as well as the underlying molecular mechanisms of photothermal therapy-induced T24 cell death. Materials and methods: T24 cells were treated with different doses of Au-Ag@PDA NPs followed by 808 nm laser irradiation, and the effects on cell proliferation, cell cycle, apoptosis, and autophagy were analyzed. To confirm the mechanisms of inhibition, real-time PCR and Western blot analysis were used to evaluate markers of cell cycle, apoptosis, autophagy, and the AKT/ERK signaling pathway. Moreover, we evaluated the effects of the treatment on mitochondrial membrane potential and ROS generation to confirm the underlying mechanisms of inhibition. Finally, we tested the T24 tumor inhibitory effects of Au-Ag@PDA NPs plus laser irradiation in vivo using a xenograft mouse model. Results: Au-Ag@PDA NPs, with appropriate laser irradiation, dramatically inhibited the proliferation of T24 cells, altered the cell cycle distribution by increasing the proportion of cells in the S phase, induced cell apoptosis by activating the mitochondria-mediated intrinsic pathway, and triggered a robust autophagy response in T24 cells. Moreover, Au-Ag@PDA NPs decreased the expression of phosphorylated AKT and ERK and promoted the production of ROS that function upstream of apoptosis and autophagy. In addition, Au-Ag@PDA NP-mediated photothermolysis also significantly suppressed tumor growth in vivo. Conclusion: This preclinical study can provide a mechanistic basis for Au-Ag@PDA NP-mediated photothermal therapy toward promotion of this method in the clinical treatment of bladder cancer.