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Nanomedicine (nanomedicine) is a drug carrier with special functions, which can realize targeted drug delivery, controlled release and multimodal imaging. Nanodrugs can overcome the problem of multidrug resistance (multidrug resistance, MDR) and improve the efficacy and safety of chemotherapeutic drugs. MDR refers to the phenomenon that tumor cells develop tolerance to one or more chemotherapeutic drugs, leading to chemotherapy failure. The mechanisms of MDR include tumor cell heterogeneity, changes of tumor microenvironment, overexpression of cell membrane transporproteins, abnormalities of apoptosis signaling pathways, and enhanced DNA repair capacity.