A visible-light-controlled platform for prolonged drug release based on Ag-doped TiO₂ nanotubes with a hydrophobic layer

In this work, a visible-light-controlled drug release platform was constructed for localized and prolonged drug release based on two-layer titania nanotubes (TNTs) fabricated using by an in situ voltage up-anodization process. The visible-light photocatalytic activity is improved by loading Ag onto the TNTs by NaBH₄ reduction. Then, the TNTs containing Ag nanoparticles were modified with dodecanethiol (NDM) to create a hydrophobic layer. To demonstrate the visible-light-controlled drug release, the Zn²⁺ release behavior of the samples was investigated. In the initial 12 h, TNTs without NDM displayed a faster release rate with 29.4% Zn²⁺ release, which was more than three times that of the TNTs with NDM (8.7% Zn²⁺ release). Upon visible-light illumination, drug release from the sample coated with NDM was shown to increase due to the photocatalytic decomposition of NDM. The amount of released Zn²⁺ for this sample increased up to 71.9% within 12 h, indicating visible-light-controlled drug release. This drug release system may exhibit promising application as a localized, prolonged drug delivery platform.