Fabrication of Rhenium Disulfide/Mesoporous Silica Core–Shell Nanoparticles for a pH-Responsive Drug Release and Combined Chemo-Photothermal Therapy

Abstract

A stimuli-responsive drug delivery nanocarrier with a core−shell structure combining photothermal therapy and chemotherapy for killing cancer cells was constructed in this study. The multifunctional nanocarrier ReS 2 @mSiO 2 -RhB entails an ReS 2 hierarchical nanosphere coated with a fluorescent mesoporous silica shell. The three-dimensional hierarchical ReS 2 nanostructure is capable of effectively absorbing nearinfrared (NIR) light and converting it into heat. These ReS 2 nanospheres were generated by a hydrothermal synthesis process leading to the selfassembly of few-layered ReS 2 nanosheets. The mesoporous silica shell was further coated on the surface of the ReS 2 nanospheres through a surfactant-templating sol−gel approach to provide accessible mesopores for drug uploading. A fluorescent dye (Rhodamine B) was covalently attached to silica precursors and incorporated during synthesis in the mesoporous silica walls toward conferring imaging capability to the nanocarrier. Doxorubicin (DOX), a known cancer drug, was used in a proof-of-concept study to assess the material's ability to function as a drug delivery carrier. While the silica pores are not capped, the drug molecule loading and release take advantage of the pH-governed electrostatic interactions between the drug and silica wall. The ReS 2 @mSiO 2 -RhB enabled a drug loading content as high as 19.83 mg/g doxorubicin. The ReS 2 @mSiO 2 -RhB-DOX nanocarrier's cumulative drug release rate at pH values that simulate physiological conditions showed significant pH responsiveness, reaching 59.8% at pH 6.8 and 98.5% and pH 5.5. The in vitro testing using HeLa cervical cancer cells proved that ReS 2 @mSiO 2 -RhB-DOX has a strong cancer eradication ability upon irradiation with an NIR laser owing to the combined drug delivery and photothermal effect. The results highlight the potential of ReS 2 @mSiO 2 -RhB nanoparticles for combined cancer therapy in the future.