Synthesis of a core/satellite-like multifunctional nanocarrier for pH- and NIR-triggered intracellular chemothermal therapy and tumor imaging

Abstract

Here, we have reported a core/satellite-like multifunctional nanocarrier for pH- and NIR-triggered synergistic chemothermal therapy and tumor imaging. In this system, upconversion nanoparticles (UCNPs), which have an average diameter of 23 nm, were first synthesized by a classic high-temperature solvent method and subsequently used as the imaging cores to direct the coating of mesoporous silica shells. The obtained mesoporous silica coated core–shell nanoparticles (UCNP@mSiO₂) have a uniform pore size (4.2 nm) and excellent DOX loading ability (85.3 μmol g⁻¹ SiO₂), which makes UCNP@mSiO₂ a good carrier. In order to finally obtain this core/satellite-like system (DOX@UCNP@mSiO₂–AuNRs), gold nanorods (AuNRs) with a positive charge of 15 mV were subsequently capped on the negatively charged DOX loaded UCNP@mSiO₂ (−30 mV) via electrostatic interactions. Under low-pH conditions (e.g. pH 4.9), the charge of mesoporous silica changed to −10.8 mV, leading to the separation of AuNRs and the release of entrapped DOX. Moreover, the present AuNRs can effectively convert NIR light (780 nm) into heat, and the increased temperature is as high as 20 °C under the laser power density of 2.0 W cm⁻². This study showed that this system has excellent imaging ability and synergistic chemothermal therapy effect. A versatile synergistic therapy system such as DOX@UCNP@mSiO₂–AuNRs is expected to have wide biomedical applications and may be particularly useful for synergistic tumor therapy.