Phthalocyanine‐Conjugated Upconversion NaYF₄:Yb³⁺/Er³⁺@SiO₂ Nanospheres for NIR‐Triggered Photodynamic Therapy in a Tumor Mouse Model

Abstract

Photodynamic therapy (PDT) has garnered immense attention as a minimally invasive clinical treatment modality for malignant cancers. However, its low penetration depth and photodamage of living tissues by UV and visible light, which activate a photosensitizer, limit the application of PDT. In this study, monodisperse NaYF4:Yb3+/Er3+ nanospheres 20 nm in diameter, that serve as near‐infrared (NIR)‐to‐visible light converters and activators of a photosensitizer, were synthesized by high‐temperature co‐precipitation of lanthanide chlorides in a high‐boiling organic solvent (octadec‐1‐ene). The nanoparticles were coated with a thin shell (≈3 nm) of homogenous silica via the hydrolysis and condensation of tetramethyl orthosilicate. The NaYF4:Yb3+/Er3+@SiO2 particles were further functionalized by methacrylate‐terminated groups via 3‐(trimethoxysilyl)propyl methacrylate. To introduce a large number of reactive amino groups on the particle surface, methacrylate‐terminated NaYF4:Yb3+/Er3+@SiO2 nanospheres were modified with a branched polyethyleneimine (PEI) via Michael addition. Aluminum carboxyphthalocyanine (Al Pc‐COOH) was then conjugated to NaYF4:Yb3+/Er3+@SiO2‐PEI nanospheres via carbodiimide chemistry. The resulting NaYF4:Yb3+/Er3+@SiO2‐PEI‐Pc particles were finally modified with succinimidyl ester of poly(ethylene glycol) (PEG) in order to alleviate their future uptake by the reticuloendothelial system. Upon 980 nm irradiation, the intensive red emission of NaYF4:Yb3+/Er3+@SiO2‐PEI‐Pc‐PEG nanoparticles completely vanished, indicating efficient energy transfer from the nanoparticles to Al Pc‐COOH, which generates singlet oxygen (1O2). Last but not least, NaYF4:Yb3+/Er3+@SiO2‐PEI‐Pc‐PEG nanospheres were intratumorally administered into mammary carcinoma MDA‐MB‐231 growing subcutaneously in athymic nude mice. Extensive necrosis developed at the tumor site of all mice 24–48 h after irradiation by laser at 980 nm wavelength. The results demonstrate that the NaYF4:Yb3+/Er3+@SiO2‐PEI‐Pc‐PEG nanospheres have great potential as a novel NIR‐triggered PDT nanoplatform for deep‐tissue cancer therapy.

Mesoporous Silica Modified Luminescent Gd₂O₃:Eu Nanoparticles: Physicochemical and Luminescence Properties

“…These surface formed high vibrational energy quenching sites enhanced the nonradiative transition pathways and suppressed the photoluminescence efficiency of the NPs. These results are in excellent agreement with the previously published reports [30,50,52,[63][64][65][66]. Additionally, the luminescent intensity is also associated to the structural characteristics such as crystal field effect, that is closely related to the structure and its symmetry, oxygen vacancies which also act as a quenching center for photoluminescence [67].…”

Detecting Variable Resistance by Fluorescence Intensity Ratio Technology

“…772042) mixed phase NaYF 4 [35,36], as shown in Figure 2b. The up-conversion (UC) photoluminescence spectra of the sensor was measured with varying current under a fixed pump power (160.8 mW/mm 2 ), among which, three emission bands were respectively ascribed to 2 H 11/2 → 4 I 15/2 (524 nm), 4 S 3/2 → 4 I 15/2 (543 nm), and 4 F 9/2 → 4 I 15/2 (658 nm) transitions of Er 3+ ions [37,38,39], as depicted in Figure 2c. The luminescence intensity of three UC emission bands decreased with the increasing current, as described in Figure 2d.…”

Drug Delivery Systems for Phthalocyanines for Photodynamic Therapy

“…To achieve biocompatibility and water dispersibility, they are commonly subjected to surface modification with silica, porous silica, biocompatible polymers or hydrophilic functional groups (193). The main advantages of these approaches are possibility to connect tumor-targeting biomolecules and covalently bind or encapsulate molecules of PS such as various PCs and NPCs (194,195). After the delivery of nanoparticles into the cancer tissue, light with deep tissue penetration (such as infrared lasers) is applied.…”