To investigate the significance of modified gold nanocages (GNCs) in photothermal therapy and radiosensitivity enhancement for murine mammary carcinoma 4T1 cells.

A molecule probe, CD₄₄-PEG-GNCs, was constructed on the basis of GNCs. Inductively coupled plasma mass spectrometry (ICP-MS) and transmission electron microscopy (TEM) were used to analyze Au uptake by 4T1 cells. The cell counting kit-8(CCK-8) assay was used to determine the impact of the probe on the viability of 4T1 cells. The CCK-8 assay and the Hoechst/PI double staining were used to evaluate the photothermal killing effects of near infrared laser (NIR). The colony forming assay and the Hoechst/PI double staining were used to measure the viability of 4T1 cells after irradiation with 6 MV of X-ray.

ICP-MS and TEM showed that 4T1 cells had an uptake of a large number of GNCs, in which the number of CD₄₄-PEG-GNCs taken up by 4T1 was 3-4 times larger than that of PEG-GNCs. The cell toxicity assay revealed that in a certain range of concentration, GNCs showed little effect on the viability of 4T1 cells, which was reduced to 81.2% in 48 hours. The CCK-8 assay, the Hoechst/PI double staining, and the colony forming assay showed that after NIR irradiation and radiotherapy, large-scale apoptosis was induced in CD₄₄-PEG-GNCs-contained tumor cells by photothermal therapy combined with radiotherapy, which had substantially better outcomes than other groups.

The GNC-based molecular probe actively targets 4T1 cells with little cytotoxicity, indicating that it enhances the sensitivity of tumor towards photothermal therapy and radiotherapy.

Molecular probe; Photothermal therapy; Radiosensitivity; Breast neoplasms