Effects of template removal on both morphology of mesoporous silica-coated gold nanorod and its biomedical application

Abstract

Mesoporous silica-coated Au nanorods (Au_rod@SiO₂) have recently attracted considerable interest in nanomedicine, and the template removal procedure is crucial for the preparation of such hybrid nanostructure. Herein, two kinds of typical extraction solvents, i.e., NH₄NO₃–CH₃OH and HCl–CH₃OH, were separately used to extract the surfactant cetyltrimethylammonium bromide (CTAB) from the obtained Au_rod@SiO₂. The results show that CTAB molecules could be completely removed from the pores of Au_rod@SiO₂ without damaging the internal Au nanorod by NH₄NO₃–CH₃OH, while Au_rod@SiO₂ treated with HCl–CH₃OH suffered from both poor extraction efficiency and the shape transformation of Au nanorod due to selective etching in the presence of oxygen. In addition, the consequent drug loading experiment shows that Au_rod@SiO₂ extracted by NH₄NO₃–CH₃OH possesses a larger drug loading capacity with a loading efficiency of 82.5%. Furthermore, the in vitro photo-thermal therapy experiment shows that Au_rod@SiO₂ extracted by NH₄NO₃–CH₃OH is more efficient in killing the YCC-2 gastric cancer cells as compared with that extracted by HCl–CH₃OH.