Controlled synthesis of gadolinium fluoride upconversion nanoparticles capped with oleic acid or polyethylene glycol molecules via one-step hydrothermal method and their toxicity to cancer cells

Abstract

Cancer is one of the major diseases that threaten human life. Upconversion nanoparticles (UCNPs) are one of the new nanomaterials that are expected to detect and treat cancer. One-step hydrothermal method can synthesize UCNPs with controllable physical and chemical properties and low biotoxicity. In this work, oleic acid (OA) and polyethylene glycol (PEG)–modified NaGdF4/GdF3:Yb,Er UCNPs were synthesized by one-step hydrothermal method. And the as-prepared UCNPs were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS), Fourier transform infrared spectroscopy (FTIR), and by using superconductor quantum interference devices (SQUID). The cytotoxicity of the modified NaGdF4/GdF3:Yb,Er UCNPs was evaluated. The results show that OA-modified UCNPs are hexagonal NaGdF4 phase, and PEG-modified UCNPs is orthorhombic GdF3 phase respectively. The particle size of OA-modified and PEG-modified UCNPs is about 15 nm and about 30 nm, respectively. The modified UCNPs have good magnetic properties and strong upconversion luminescence properties (UCL), wherein PEG-modified UCNPs perform slightly better capabilities than those of OA-modified UCNPs. When the concentration of nanoparticles increased from 62.5 to 500 μg/mL, OA-NaGdF4:Yb,Er showed a certain cytotoxicity and exhibited dose-effect relationship. However, PEG-GdF3:Yb,Er did not display obvious cytotoxicity. Therefore, PEG-modified UCNPs may be more suitable for application in oncology field.