A novel microwave stimulus remote-controlled anticancer drug release system based on Janus TiO_2-x&mSiO₂ nanocarriers

In this work, we used a simple method to construct Janus-shaped TiO_2-x&mSiO₂ nanoparticles composed of gray-black titanium dioxide (TiO_2-x) and mesoporous silica (mSiO₂) serving as carriers to improve the microwave-controlled release performance. In the composite materials, on one hand, the rod-shaped mSiO₂ could realize high-efficiency drug loading, on the other hand, spherical TiO_2-x featuring oxygen vacancy acted as the main microwave absorber. The overall spatial separation between titanium dioxide and silicon dioxide was crucial to enhance microwave conversion efficiency. The Janus-liked nanomaterial was made up of TiO_2-x nanosphere with a diameter of approximately 180 nm on one end and rod-shaped mesoporous silica with about 220 nm in length and 100 nm in diameter on the other end, and the specific surface area of the entire material was 203.25 m²/g. Meanwhile, the cumulative doxorubicin hydrochloride (DOX) loading rate of the carrier reached up to 38 wt% after 24 h. The loading process of the DOX was exothermic, and the noncovalent interaction between the DOX and Janus TiO_2-x&mSiO₂ carrier was mainly van der Waals force. Furthermore, the rates of drug release at 24 h were up to 61 wt%, 69 wt% and 89 wt% at pH 7.0, 5.0 and 3.0, respectively. After microwave stimulation at pH 7.0, the rate of drug release increased observably from 61% to 88% compared to that of non-microwave irradiation. The order of the microwave thermal conversion capability of the samples was Janus TiO_2-x&mSiO₂ > Janus TiO₂&mSiO₂ > core-shell TiO_2-x@mSiO₂. Besides, cytotoxicity tests indicated that Janus TiO_2-x&mSiO₂ nanoparticles had good biocompatibility. Therefore, the multifunctional carrier of the Janus-shaped configuration could not only release drugs under pH control, but also be further triggered by microwave stimulation. The Janus-shaped TiO_2-x&mSiO₂ nanoparticles will look forward to laying foundation to the application in drug delivery systems.