Terbium-Labeled Gold Nanoparticles as Nanoscale Brachytherapy Agents Against Breast Cancer.

Due to their intriguing emission profile, Terbium-161 (Tb) radiopharmaceuticals seem to bring significant advancement in theranostic applications to cancer treatment. The combination of Tb with nanoscale brachytherapy as an approach for cancer treatment is particularly advantageous and promising. Herein, we propose the application of a hybrid nanosystem comprising gold decorated (Au@TADOTAGA) iron oxide nanoflowers as a form of injectable nanobrachytherapy for the local treatment of breast cancer. More specifically, Au@TADOTAGA and NFAu@TADOTAGA NPs were efficiently radiolabeled with Tb, and their in vitro stability was assessed up to 21 d post-radiolabeling. Furthermore, their cytotoxic profile against 4T1 breast cancer cells was evaluated, and their ex vivo biodistribution characteristics were revealed after intratumoral injection in the same animal model. The enhanced retention at the tumor site urged us to evaluate the therapeutic effect of the [Tb]Tb-NFAu@TADOTAGA nanosystem after intratumoral administration to 4T1-tumor-bearing mice, over a period of 24 days. Three different therapeutic protocols were performed in order to identify which therapeutic approach would offer the optimum results and identify the proposed nanosystem as a promising nanoscale brachytherapy agent.