Degradable mesoporous semimetal antimony nanospheres for near-infrared II multimodal theranostics

Metallic and semimetallic mesoporous frameworks are of great importance owing to their unique properties and broad applications. However, semimetallic mesoporous structures cannot be obtained by the traditional template-mediated strategies due to the inevitable hydrolytic reaction of semimetal compounds. Therefore, it is yet challenging to fabricate mesoporous semimetal nanostructures, not even mention controlling their pore sizes. Here we develop a facile and robust selective etching route to synthesize monodispersed mesoporous antimony nanospheres (MSbNSs). The pore sizes of MSbNSs are tunable by carefully controlling the partial oxidation of Sb nuclei and the selective etching of the as-formed Sb2O3. MSbNSs show a wide absorption from visible to second near-infrared (NIR-II) region. Moreover, PEGylated MSbNSs are degradable and the degradation mechanism is further explained. The NIR-II photothermal performance of MSbNSs is promising with a high photothermal conversion efficiency of similar to 44% and intensive NIR-II photoacoustic signal. MSbNSs show potential as multifunctional nanomedicines for NIR-II photoacoustic imaging guided synergistic photothermal/chemo therapy in vivo. Our selective etching process would contribute to the development of various semimetallic mesoporous structures and efficient multimodal nanoplatforms for theranostics.

Automated summary

Metallic and semimetallic mesoporous frameworks have unique properties and wide applications. However, semimetallic mesoporous structures are difficult to obtain using traditional methods. In this study, monodisperse mesoporous antimony nanospheres were successfully synthesized using a selective etching route, with tunable pore sizes. The antimony nanospheres showed wide absorption in the visible to second near-infrared (NIR-II) region, with promising NIR-II photothermal performance and photoacoustic signal. These multifunctional nanospheres could be used for synergistic photothermal/chemo therapy guided by NIR-II photoacoustic imaging.