Abstract Background: Multimodal cancer therapy has garnered significant interest due to its ability to target tumor cells from various perspectives. The advancement of novel nano-delivery platforms represents a promising approach for improving treatment effectiveness while minimizing detrimental effects on healthy tissues. Methods: This study aimed to develop a multifunctional nano-delivery system capable of simultaneously delivering an anti-cancer drug, a radiosensitizer agent, and a targeting moiety (three-in-one) for the triple combination therapy of colorectal cancer (CRC). This unique nano-platform, called Apt-PEG-DOX/ZIF-8@GQD, encapsulated both doxorubicin (DOX) and graphene quantum dots (GQDs) within the zeolitic imidazolate framework-8 (ZIF-8). To enhance the safety and anti-cancer potential of the platform, heterobifunctional polyethylene glycol (PEG) and an epithelial cell adhesion molecule (EpCAM) aptamer were conjugated with the system, resulting in the formation of targeted Apt-PEG-DOX/ZIF-8@GQD NPs. The physical and chemical characteristics of Apt-PEG-DOX/ZIF-8@GQD were thoroughly examined, and its therapeutic efficacy was evaluated in combination with radiotherapy (RT) against both EpCAM-positive HT-29 and EpCAM-negative CHO cells. Furthermore, the potential of Apt-PEG-DOX/ZIF-8@GQD as a tumor-specific, radio-enhancing, non-toxic, and controllable delivery system for in vivo cancer treatment was explored using immunocompromised C57BL/6 mice bearing human HT-29 tumors. Results: The large surface area of ZIF-8 (1013 m2 g-1) enabled successful loading of DOX with an encapsulation efficiency of approximately ∼90%. The synthesis of Apt-PEG-DOX/ZIF-8@GQD resulted in uniform particles with an average diameter of 100 nm. This targeted platform exhibited rapid decomposition under acidic conditions, facilitating an on-demand release of DOX after endosomal escape. In vitro experiments revealed that the biocompatible nano-platform induced selective toxicity in HT-29 cells by enhancing X-ray absorption. Moreover, in vivo experiments demonstrated that the therapeutic efficacy of Apt-PEG-ZIF-8/DOX@GQD against HT-29 tumors was enhanced through the synergistic effects of chemotherapy, radiotherapy, and targeted therapy, with minimal side effects. Conclusion: The combination of Apt-PEG-DOX/ZIF-8@GQD with RT as a multimodal therapy approach demonstrated promising potential for the targeted treatment of CRC and enhancing therapeutic effectiveness. The co-delivery of DOX and GQD using this nano-platform holds great promise for improving the outcome of CRC treatment.

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