Self-oxygenating GMZ@HA nanocarriers enhance doxorubicin cytotoxicity in hypoxic breast cancer

Abstract

Tumor hypoxia has been recognized as a significant challenge in cancer therapy, with certain chemotherapeutic agents such as doxorubicin (DOX) exhibiting reduced efficacy under low oxygen conditions. In the present study, a multifunctional nanocomposite (GMZ@HA-DOX) was developed to alleviate tumor hypoxia and enhance DOX efficacy in breast cancer treatment. Graphene oxide (GO) nanosheets were functionalized with manganese dioxide (MnO₂) nanoparticles and hyaluronic acid-coated zinc peroxide (ZnO₂@HA), onto which DOX was subsequently loaded. Under the acidic conditions characteristic of the tumor microenvironment, ZnO₂@HA generated hydrogen peroxide (H₂O₂), which was catalytically converted into oxygen by MnO₂, thereby increasing local oxygen levels. Uniform dispersion of MnO₂ (approximately 10 nm) and ZnO₂ (approximately 20 nm) on the GO matrix was confirmed by electron microscopy and energy-dispersive X-ray analysis, with a DOX loading efficiency of approximately 50 %. The nanocomposite exhibited sustained, pH-dependent drug release, with higher DOX release at pH 5.4 than at pH 7.4 over 72 h, supporting tumor-specific delivery. The oxygen-generating capability of the nanocomposite was assessed using an oxygen probe assay, which revealed a 2.7- to 3-fold increase in oxygen production compared to control conditions. In vitro experiments using MCF-7 breast cancer cells under normoxic and hypoxic conditions demonstrated that treatment with the nanocomposite reduced cell viability, lowered IC₅₀ value of DOX, and enhanced intracellular drug accumulation. Enhanced reactive oxygen species production, increased apoptosis, and inhibited cell migration were also observed, while minimal toxicity was detected in HEK-293 renal cells. Furthermore, in an ex vivo multicellular model simulating in vivo tumor tissue, the nanocomposite was shown to penetrate deeply and effectively destroy tumor cells. These findings indicate that the oxygen-generating nanocomposite overcomes hypoxia-induced drug resistance and significantly improves the targeted delivery and therapeutic efficacy of DOX, representing a promising strategy for treating hypoxic tumors.