Hydroxyapatite/mesoporous silica coated gold nanorods with improved degradability as a multi-responsive drug delivery platform

In this study, gold nanorods/mesoporous silica/hydroxyapatite (Au/SiO 2 /HAP) hybrid nanoparticles with AuNR core and SiO 2 /HAP hybrid inorganic shell for multi-responsive drug delivery had been prepared. The morphology and structure of the nanoparticles were characterized by TEM, XPS, XRD, FT-IR and N 2 adsorption-desorption isotherms. The degradation of the hybrid nanoparticles could be significantly improved by the dissolution of HAP from the hybrid skeleton in acid environment. In vitro drug release results indicated that Au/SiO 2 /HAP nanoparticles exhibited high drug loading efficiency, excellent near-infrared (NIR)- and pH-responsive drug release properties. Compared to the drug release of Au/SiO 2 nanoparticles over 12   h (about 6.35%), Au/SiO 2 /HAP nanoparticles displayed a higher drug release of 37.62% upon NIR irradiation at pH   4.5 due to the NIR-responsiveness of AuNRs and the pH-responsiveness of HAP in acid media. The cell viability results also indicated that the Au/SiO 2 /HAP nanoparticles exhibited the excellent biocompatibility. The present paper provides a facile route to fabricate a hybrid drug carrier with high drug loading efficiency, excellent pH sensitivity, NIR-sensitivity, biodegradability and biocompatibility.