Ultra-high thermally stable gold nanorods/radial mesoporous silica and their application in enhanced chemo-photothermal therapy.

In this work, gold nanorods embedded in ultra-thick silica shells with radial mesopores (AuNR/R-SiO 2 ) were successfully synthesized in an ethanol/water solution. By optimizing the concentration of CTAB and the volume of ethanol, a shell thickness up to 83 nm was realized. Taking advantage of the ultra-thick silica shell, AuNR/R-SiO 2 exhibited ultra-high thermal stability-could retain the integrity and photothermal effects even after 800 °C thermal annealing, providing inspiring sights into the application under some extreme conditions. After continuous irradiation for twenty times, the photothermal effects of AuNRs coated with R-SiO 2 still remained perfect without performance degradation and shape change. Besides, abundant mesopores could effectively improve the photothermal conversion efficiency of AuNRs. AuNR/R-SiO 2 exhibited an outstanding loading capacity up to 2178 mg g -1 with doxorubicin (DOX) as the model drug, and the release behaviors could be nicely controlled by acidity and near-infrared (NIR) laser to achieve the "On-demand" mode. In vitro experiments showed that AuNR/R-SiO 2 were biocompatible and easy to be internalized by HeLa cells. In addition, due to the ultra-thick silica shell, the effect of the combined chemo-photothermal therapy using AuNR/R-SiO 2 /DOX was significantly enhanced, showing a higher therapeutic efficiency than single chem- or photothermal therapy. It was worth noting that AuNR/R-SiO 2 are effective and promising for drug delivery and tumor therapy.