Metal-coordinated nanodrugs based on natural products for cancer theranostics

Metal-coordinated nanodrugs based on natural products have recently attracted widespread interests in cancer theranostics. Natural products have unparalleled advantages due to abundant active groups, facile modification/functionalization, low cost, unique pharmacological activity and good biocompatibility. More importantly, the active groups on the natural products could coordinate with various metal ions to construct the metal-coordinated nanodrugs. Meanwhile, coordination-driven self-assembly of natural products-based nanodrugs with facile and green preparation methods, optimized structures and properties, stable blood circulation and responsiveness to tumor microenvironment could be used as multifunctional cancer theranostic nanoplatforms, which have emerged as promising candidates for nanodrugs. Herein, we have categorized various origins of natural products-based nanodrugs, mainly on coordination interactions between natural products and metal ions. Then the advanced applications of these nanodrugs in the areas of cancer therapy, cancer diagnosis and synergetic treatment are summarized. Additionally, the tumor-specific intratumorally coordinated natural products were emphasized. Finally, we thoroughly discussed the main limitations, challenges and prospects of metal-coordinated nanodrugs based on natural products for cancer theranostics. Based on summarizing extensive researches, our review will provide the existing and new researchers a foundation from which to promote clinical applications of metal-coordinated nanodrugs based on natural products and advance cancer theranostics.