Biocompatible upconverting core/shell/shell nanoparticles with enhanced red emission for application in bioimaging and cancer therapy

Cancer therapy and diagnostics have become one of the most promising and studied topics in terms of nanomedicine. Focusing on therapeutic applications, the application of nanoparticles (NPs) as drug delivery vehicles or... [ view full abstract ]

Cancer therapy and diagnostics have become one of the most promising and studied topics in terms of nanomedicine. Focusing on therapeutic applications, the application of nanoparticles (NPs) as drug delivery vehicles or multimodal contrast agents is of major importance [1]. In this work, we report the thermal decomposition synthesis of NaGdF₄:Er³⁺@NaYbF₄@NaGdF₄ core/shell/shell upconverting nanoparticles (UCNPs) as multimodal imaging agents. X-ray diffraction (XRD), scanning electron microscopy (SEM) and photoluminescence (PL) spectroscopy were used to characterize UCNPs (Fig. 1). Further surface functionalization was subsequently accomplished using a well-known Tween80 nonionic surfactant which converts hydrophobic nanoparticles to hydrophilic ones. The concentration of Er³⁺ in core NaGdF₄ matrix was varied and optical properties of obtained nanoparticles was investigated by Edinburgh Instruments FLS980 spectrometer. Compared with NaGdF₄:Er³⁺ active-core NPs, the two order of magnitude enhancement of total integrated emission intensity was obtained in the core/shell/shell NPs. Importantly, the red UC emission of 653 nm in core/shell/shell NPs is greatly increased compared to the core and core/shell samples under 980 nm excitation at room temperature. In contrast to green and blue light, red light (600–700 nm) can deeply penetrate into biotissues owing to the lack of efficient endogenous absorbers [2]. Furthermore, cell viability assay XTT was performed to measure cellular metabolic activity after 24 hours treatment with different concentrations of UCNPs. Nanoparticles have no significant influence on viability of cells after incubation with 0.01 mg/mL and 0.5 mg/mL UCNPs solutions; however a slight decrease of viability was observed after incubation with 0.1 mg/mL UCNPs solution. Smart design of multifunctional nanocomposite and further studies are still essential to generate sufficient data for better understanding of long-term toxicity and safety of the UCNPs before introducing their wide applicability in medicine.

Reference:

[1] L. Y. Ang et al., Nanomedicine, 6, 7 (2011)

[2] H. Lin et al., Sci. Rep., 6, 16, (2016)