Three-Dimensionally Controllable Synthesis of Multichannel Silica Nanotubes and Their Application as Dual Drug Carriers

Three-dimensionally controllable multichannel silica nanotubes (MC-SNTs) have been constructed. Quaternary ammonium type (C_nH_2n+1(CH₃)₃N⁺) surfactants were used as structure-directing agents (SDAs) in basic ammonia. A low concentration of block copolymer HO(CH₂CH₂O)₂₀[CH₂CH(CH₃)O]₇₀(CH₂CH₂O)₂₀H (P123) was employed as an additive. The length, diameter, and pore size of MC-SNTs can be finely controlled in the range of 50 nm to 5 μm, 50 nm to 350 nm, and 2 nm to 3 nm by changing the molar ratio of P123 and SDA, the concentration of ammonia, and the length of carbon chain of SDAs, respectively. Observations based on transmission electron microscopy confirmed the role of P123 and ammonia in the self-assembly of micelles of SDA. Compared with the one-pot method reported previously, the aspect ratios (ARs; length/diameter) of obtained MC-SNTs were tunable in a wide range of approximately 1 to 100. The tunable MC-SNTs were used as dual drug-delivery carriers for anticancer drug doxorubicin (Dox) and anti-inflammatory drug ibuprofen (Ibu). Results of release behavior and toxicity to cancer cells of Dox-Ibu-loaded MC-SNTs with different ARs revealed that Dox and Ibu were successfully codelivered and did not interfere with each other. The produced MC-SNTs with larger AR values of showed advantages in the amount of accumulated dual drugs, the duration time of release, and inhibition of the growth of HeLa cells.