Multifunctional NaYF4 : Yb3+,Er3+@Ag core/shell nanocomposites: integration of upconversion imaging and photothermal therapy

Abstract

Here we present the synthesis of core-shell structured hexagonal-phase NaYF 4 : Yb 3+ ,Er 3+ @Ag nanoparticles (NPs) and their unique bio-functional properties. The structure and morphology of the NPs are confirmed by X-ray powder diffraction (XRD), transmission electron microscopy (TEM), scanning electron microscopy (SEM) and Fourier transform infrared (FT-IR) measurements. They displayed both strong 2 H 11/2 / 4 S 3/2 -4 I 15/2 (green) and 4 F 9/2 -4 I 15/2 (red) upconversion luminescence (UCL) and photothermal transfer properties under the excitation of a continuous 980 nm laser diode. Furthermore, the UCL intensity ratio of 2 H 11/2 -4 I 15/2 to 4 S 3/2 -4 I 15/2 acted as a temperature sensor due to the low energy gap between 2 H 11/2 and 4 S 3/2 ($740 cm À1 ). After coating with the silver shell, the cytotoxicity of the composite NPs was reduced largely in contrast to the pure NaYF 4 : Yb 3+ ,Er 3+ NPs. HepG2 cells from human hepatic cancer and BCap-37 cells from human breast cancer incubated with the composite NPs in vitro were found to undergo photothermally induced death on exposure to 980 nm NIR light, and the optimum mortality approaches 95% with a power density of 1.5 W cm À2 which is much lower than that reported for Au nanoshells and Au nanorods. Overall, this class of core/shell NPs is expected to be an attractive therapeutic agent for tumor ablation with bioimaging and thermal detection in real time.

Upconversion Nanoparticles for Light-Activated Therapy

“…Song et al [190] fabricated NaYF 4 :Yb/Er UCNP@Ag core-shell nanocomposites and tuned the surface plasmon absorption of Ag shell to NIR region. The UCL intensity ratio of 2 H 11/2 -4 I 15/2 to 4 S 3/2 -4 I 15/2 was sensitive to temperature and thus was utilized to achieve thermal detection in real time, while the Ag shell was employed for NIR-induced PTT.…”

“…UCNPs generally have limited capability to convert light directly into heat because of the low extinction coefficient of lanthanide ions [62] and are thus coupled to photoabsorbers possessing high photothermal conversion efficiency, including Au nanomaterials [187][188][189], Ag nanomaterials [190], CuS nanoparticles [191], and organic dyes [91,192] in PTT treatment of diseases. In this context, UCNPs are mainly responsible for multimodal imaging as nanoprobes.…”

Upconversion Nanoparticle-Based Nanocomposites

“…In addition, Kannan et al introduced gold nanorods decoration on NaYF 4 :Yb/Tm upconversion nanoparticles by functionalizing the upconversion nanoparticles with polyamidoamine generation 1 (PAMAM G1) dendrimer, followed by a single-step seed-mediated growth of long-range gold nanorods to enhance "biological window" upconversion emission [161]. Dong et al [165] present the synthesis of core-shell-structured hexagonal-phase NaYF 4 :Yb 3+ ,Er 3+ @Ag nanoparticles and their unique biofunctional properties. The approach for the preparation of multi-functional NaYF 4 :Yb 3+ ,Er 3+ @Ag nanoparticles is as following.…”

Modification of Ag shell on upconversion populating paths of NaYF4:Yb3+,Er3+@Ag nanocomposites

“…Taking advantage of the surface plasmon resonance property of noblematal nanomaterials, enhancing the luminescent properties can be achieved. In our recent work [10], we prepared an NaYF 4 @Ag core/shell structured nanocomposites which allows simultaneously working of both bioimaging and photothermal therapy in a system, because both plasmatic absorption of Ag outer shells and upconversion excitation of core could be successfully tuned to 980 nm.…”