To investigate the radiosensitizing effect of mesoporous silica-encapsulated gold nanorods (GNRs@mSiO₂) combined with 6 MV X-ray on human triple-negative breast cancer MDA-MB-231 cells and its possible mechanism.

A transmission electron microscope was used to analyze the morphology and intracellular distribution of GNRs@mSiO₂. An atomic absorption spectrophotometer was used to evaluate the uptake of GNRs@mSiO₂ by cells. The CCK-8 assay was used to measure the cytotoxicity of different concentrations of GNRs@mSiO₂. The colony formation assay was used to determine the effect of GNRs@mSiO₂ on the radiosensitivity of cells. Flow cytometry was used to measure the cell cycle, apoptosis, and the level of reactive oxygen species. Between-group comparison was made by paired t test.

The uptake of GNRs@mSiO₂ by MDA-MB-231 cells reached a peak value at 24 h, which was (7.09±0.26)-fold higher than that in the control group and significantly higher than those in other groups (P=0.002-0.014). After exposure to 12.5-50.0μg/ml GNRs@mSiO₂ for 24 h, more than 90% of the cells remained alive. The D₀, D_q, and SF₂ values in the GNRs@mSiO₂+ irradiation group were lower than those in the irradiation alone group, yielding a sensitization enhancement radio of 1.27(radio of SF₂ values). The apoptosis rate was (30.4±0.68)% in the GNRs@mSiO₂+ irradiation group. The proportion of cells in G₂/M phase was (31.25±0.75)% in the GNRs@mSiO₂+ irradiation group, which was significantly higher than those in other groups (P=0.003-0.033).

Mesoporous silica-encapsulated gold nanorods can effectively enhance the radiosensitivity of human triple-negative breast cancer MDA-MB-231 cells to 6 MV X-ray.

Mesoporous silica-encapsulated gold nanorods; Radiosensitivity; Triple-negative breast cancer cell lines