Core–Shell Structured Up-Conversion Luminescent and Mesoporous NaYF₄:Yb³⁺/Er³⁺@nSiO₂@mSiO₂ Nanospheres as Carriers for Drug Delivery

Abstract

CoreÀshell structured up-conversion luminescent and mesoporous NaYF 4 :Yb 3+ /Er 3+ @nSiO 2 @mSiO 2 nanospheres were prepared by coating mesoporous SiO 2 layers with different thicknesses on NaYF 4 :Yb 3+ / Er 3+ nanoparticles via a simple two-step solÀgel process. The obtained sample shows a typical mesoporous structure and well-dispersed spherical morphology with a narrow size distribution. The nanospheres exhibit little cytotoxicity (via MTT assay), and ibuprofen (IBU) was used as a model drug to access the release properties of the system in detail. The amount of IBU adsorbed in mesoporous channels increases with the thickness of the ordered mesoporous silica shell coated on the NaYF 4 :Yb 3+ /Er 3+ nanoparticles. The in vitro release study of IBU reveals a release profile in two steps: an initial diffusion-controlled release, followed by a slower release rate. Furthermore, upon excitation by a 980 nm near-infrared laser, the nanospheres emit green ( 2 H 11/2 and 4 S 3/2 f 4 I 15/2 ) and red ( 4 F 9/2 f 4 I 15/2 ) fluorescence of Er 3+ even after the loading of IBU. Interestingly, the emission intensity of Er 3+ in the bifunctional (mesoporous and luminescence) drug carrier increases with an increase of the cumulative released amount of the model drug (IBU). Thus, the extent of drug release can be easily identified, tracked, and monitored based on the change of the up-conversion luminescence. These results suggest that the coreÀshell structured NaYF 4 :Yb 3+ /Er 3+ @nSiO 2 @m-SiO 2 nanospheres are a promising material for controlled drug release.

Near-Infrared Light Manipulated Chemoselective Reductions Enabled by an Upconversional Supersandwich Nanostructure

“…41,42 Finally, the upconversion and catalytic functionality can be further utilized simultaneously to achieve more complicated tasks, such as photo-manipulated catalysis and indicating the progress of chemical reactions.…”

Synthesis of magnetic and upconversion nanocapsules as multifunctional drug delivery system

“…After the loading of DOX molecules, the intensity of the DOX-FeSiUCNP UCL decreased obviously, which may be attributed to the introduction of the drug molecules. The organic groups in DOX molecules with high-frequency vibrations will quench the emission of Er 3 þ greatly [26].…”

Upconversion Nanoparticles for Light-Activated Therapy

“…In the first case, UCNPs are utilized only as luminescent indicators to track nanocarriers or to monitor the release of payloads in the presence of the energy transfer process between drugs and UCNPs [124]. The release of drugs is triggered by internal or external stimuli, such as pH [125][126][127][128][129][130][131][132][133][134], temperature [135,136], and redox species [137], or the concentration gradient of drug molecules [138][139][140][141][142][143][144]. For example, Lin et al [130] attached DOX, a widely used anticancer drug, to hydrazine-functionalized NaYF 4 :Yb/Tm UCNPs via covalent conjugation.…”