Polydopamine-coated gold core/hollow mesoporous silica shell particles as a nanoplatform for multimode imaging and photothermal therapy of tumors

It is highly desirable to develop a new hybrid nanoplatform that integrates diagnosis and treatment elements for effective theranostics of tumors. Herein, we have skillfully designed a nanoplatform of polydopamine (PDA)-coated and perfluorohexane (PFH)-filled gold core/hollow mesoporous silica shell (Au@ mSiO(2)-PFH-PDA, ASPP for short) particles for photoacoustic (PA)/ultrasound (US)/computed tomography (CT)/thermal imaging and photothermal therapy (PTT) of tumors. In this work, we first synthesized Au seed particles with a diameter of 15.8 nm using a sodium citrate reduction method, and coated Au seeds with polyvinylpyrrolidone for further growth of solid silica shell/mesoporous silica outer shell onto the Au seeds. After treatment via selective etching to remove solid silica shell, amination of surface of the particles, and filling of PFH into the internal cavity of the spheres with a diameter of 182.1 nm, PDA coating was performed to render the particles with an external shell thickness of 15.1 nm. The formed hybrid particles with a size of 212.2 nm are colloidally stable and exhibit good cytocompatibility, and display excellent PA/US/CT/thermal imaging property due to the co-presence of PDA, PFH, and Au nanoparticles. Furthermore, the PDA coating renders the platform with a photothermal conversion efficiency of 61.2%, enabling effective photothermal ablation of cancer cells in vitro and a xenografted 4T1 tumor model in vivo under irradiation with an 808 nm laser. More importantly, in the primary 4T1 tumor model, intratumoral injection of the ASPP and irradiation with an 808 nm laser can also completely inhibit the occurrence of lung metastasis induced by the 4T1 tumor. The as-prepared hybrid nanoplatform may hold a great promise to be adopted for multimode imaging and PTT of tumors and inhibition of tumor metastasis.