Copper complexes mediate the in situ production of reactive oxygen species in the nucleus, enhancing the anti-tumor efficacy of PTX

• Nuclear-targeted nanoplatform delivering PTX and copper for synergistic therapy • GSH-responsive PTX release and NLS-mediated copper nuclear translocation • In situ nuclear Fenton-like reaction amplifying PTX efficacy via enhanced ROS generation and apoptosis • Superior in vitro and in vivo anti-tumor efficacy and biosafety compared to free PTX Engineering a combination chemotherapy of PTX and copper complex has advantages. PTX treatment of tumor cells can increaseH 2 O 2 , providing a substrate for copper to trigger the decomposition of H 2 O 2 through a Fenton-like reaction and to generate ROS, thereby causing DNA damage in tumor cells. However, due to the short half-life and limited diffusion distance of ROS, the anti-tumor efficacy is reduced. This problem can be overcome by delivering copper into the nucleus to achieve in situ Fenton-like reaction induction and ROS release therein. Here, we fabricated a hierarchical delivery system where PTX was connected to polyethyleneimine by disulfide bond, and then modified with a nuclear localization signal peptide. Finally, copper loading was realized by the rich amine-mediated coordination of PEI, and the Cu/PSPN nanoplatform was obtained. The results showed that Cu/PSPN exhibited an appropriate particle size (245 nm) and zeta potential (+1.88 mV), with minimal hemolytic toxicity. Cu/PSPN achieved hierarchical transport of PTX and copper in the cytoplasm and nucleus through glutathione responsiveness and NLS-mediated delivery. Cu/PSPN induced an efficient Fenton-like reaction in the nucleus, significantly enhancing the anti-tumor efficacy of PTX by increasing ROS generation and apoptosis rates to 1.82-fold and 3.89-fold those of the PTX group, respectively. Cu/PSPN also demonstrated superior anti-tumor efficacy in vivo with tumor weight and volume being approximately 6.8% and 10.5% of the free PTX group. This study provides a robust engineering strategy for significantly improving the anti-tumor efficacy of PTX based on the in situ generation of ROS in the nucleus.