Gold Nanostars Coated with Mesoporous Silica Are Effective and Nontoxic Photothermal Agents Capable of Gate Keeping and Laser-Induced Drug Release

[EN] Herein, a novel drug photorelease system based on gold nanostars (AuNSts), coated with a mesoporous silica shell and capped with paraffin as thermosensitive molecular gate, is reported. Direct measurements of the surface temperature of a single gold nanostar irradiated using a tightly focused laser beam are performed via a heat sensitive biological matrix. The surface temperature of a AuNSt increases by hundreds of degrees (degrees C) even at low laser powers. AuNSts coated with a mesoporous silica shell using a surfactant-templated synthesis are used as chemotherapeutic nanocarriers. Synthetic parameters are optimized to d avoid AuNSt reshaping, and thus to obtain nanoparticles with suitable and stable plasmonic properties for near-infrared (NIR) laser-triggered cargo delivery. The mesoporous silica-coated nanostars are loaded with doxorubicin (Dox) and coated with octadecyltrimethoxysilane and the paraffin heneicosane. The paraffin molecules formed a hydrophobic layer that blocks the pores, impeding the release of the cargo. This hybrid nanosystem exhibits a well-defined photodelivery profile using NIR radiation, even at low power density, whereas the nonirradiated sample shows a negligible payload release. Dox-loaded nanoparticles displayed no cytotoxicity toward HeLa cells, until they are irradiated with 808 nm laser, provoking paraffin melting and drug release. Hence, these novel, functional, and biocompatible nanoparticles display adequate plasmonic properties for NIR-triggered drug photorelease applications.
The authors gratefully acknowledge financial support from the Spanish Government (Projects AGL2015-70235-C2-2-R and MAT2015-64139-C4-1-R), the Generalitat Valenciana (Project PROMETEOII/2014/047), and European Union (Programme European Union Action 2 Erasmus Mundus Partnerships, Grant-2014-0870/001-001). A. Samadi and L. B. Oddershede acknowledge financial support from the Novo Nordisk Foundation (NNF14OC0011361) and from the Danish National Research Foundation (DNRF116). A. H. Montoto thanks Erasmus Mundus Programme for his PhD scholarship at EurolnkaNet project. The authors thank UPV electron microscopy and CIPF confocal and electron microscopy services for technical support.