Determination of whether multidrug nanocarriers can deliver and release loaded drugs at a predefined synergistic ratio to target cancer cells is crucial.Although there are many successful applications for delivery of multiple drugs,most current carriers are unable to achieve coordinated loading and release,leading to a drug release ratio that disagrees with the predefined loading ratio.In this work,a simple dual-drug delivery system with a flexible and controllable drug release ratio was constructed to deliver two anticancer drugs,doxorubicin (DOX) and curcumin (CUR).The drug ratio of DOX and CUR can be easily tuned for an enhanced synergistic effect,and the drugs can be released at predesigned ratios due to synchronous drug activation and nanoparticle collapse.Drug release at predefined ratios for synergistic anticancer therapy was demonstrated via in vitro and in vivo ex-periments.Therefore,the dual drug delivery system developed here provides a simple and efficient strategy for combination chemotherapy.