An Integrative Folate-Based Metal Complex Nanotube as a Potent Antitumor Nanomedicine as Well as an Efficient Tumor-Targeted Drug Carrier.

Metal-organic complexes (MOCs) are emerging developing functional materials, the different categories of metal ions and organic biomolecules provide great possibilities for the morphologies, sizes, and properties of the products. Enlightened by the previous works of folate-nickel nanotubes (FA-Ni NTs), herein, a series of metal ions are tested to coordinate with folate (FA) by the solvothermal method, among which the folate-cobalt(II) complex is formed to be a scaffold for the nanotube with the length of 150-500 nm and inner diameter of 6-11 nm, while the other metal ions fail. In vitro experiments reveal that folate-cobalt nanotubes (FA-Co NTs) have excellent antitumor activity toward tumor cells with high expression levels of folate receptor (FR), whereas they show extremely low toxicity to normal cells. Furthermore, these kinds of NTs show better antitumor ability when the anticancer drug doxorubicin is encapsulated through cell surface receptor-mediated endocytosis. Moreover, we study the fundamental pharmacokinetic profiles and biodistribution of FA-Co NTs on mice and also prove its targeting capability to tumor tissues on tumor-bearing mice using the radioactive iodine-131 (131I) tracing method. FA-Co NTs can also markedly inhibit the growth of tumor with minimal side effects when administered individually in vivo. These findings will expand the research on FA based metal complex nanomaterials as a kind of potential antitumor nanomedicine as well as a targeted drug carrier.