Synthesis and properties of nanostructures based on lanthanum fluoride for photodynamic therapy of tumors of the cranial cavity and bone tissue

Abstract

The aim of the work is the synthesis of nanostructures based on lanthanum fluoride, promising for use in photodynamic therapy of tumors in organs of cranial cavity and bone tissues; a study of their structural properties and luminescence spectra. Synthesis of LaF3:Tb3+ was carried out by coprecipitation of components from aqueous and alcoholic (methanol) solution. As precursors were used: La(NO3)3×6H2O, TbCl3, NH4F. All reagents have qualification “chemically pure”. Distilled water and methanol were used as solvent. The synthesis of nanosized magnetite in the single-domain state was performed by the Elmore method. Synthesized nanodisperse samples are characterized by XRD analysis, DTGA, TEM. The magnetic properties and spectra of UV luminescence were also studied. It has been found that the XRD-patterns of LaF3:Tb3+ samples synthesized in water and methanol do not differ fundamentally. Under the experimental conditions, the most perfect crystals of hexagonal syngony were formed during crystallization in an autoclave. Their average size was ~ 15 nm. In TEM images, the length of the crystals exceeds the width by 3–4 times. Crystals are prone to aggregation and the formation of chain structures. The UV luminescence spectrum of the synthesized nanodisperse samples in aqueous medium at the concentration of 0.5 mg/ml and excited by ultraviolet radiation is characteristic of the structure of LaF3:Tb3+. Ensembles of particles Fe3O4/LaF3:Tb3+ NCs were synthesized. Transmission electron microscopy has shown that the shapes of particles of NCs and LaF3:Tb3+ nanocrystals are fundamentally different. Particles of Fe3O4/LaF3:Tb3+ NCs have a spherical shape, which is characteristic of structures of the core-shell type. X-ray diffraction patterns of NCs confirm this conclusion. The conditions for the synthesis of NCs did not significantly change the magnetic properties of their nuclei, single-domain Fe3O4 nanoparticles (NPs). The luminescence spectrum of Fe3O4/LaF3:Tb3+ NCs differs significantly from the spectrum of samples of nanodispersed LaF3:Tb3+ both in intensity and in the structure of the bands. These spectral differences may be due to differences in structure, features of the nanocrystalline structure, the content of the LaF3:Tb3+ scintillator and Tb3+ ions in samples of LaF3:Tb3+ nanocrystals and shells of Fe3O4/LaF3:Tb3+ nanocomposites. Composites of dispersed 60S bioglass with nanodispersed crystalline LaF3:Tb3+ in the dry state, and distilled water, showed the presence of luminescence upon excitation by UV radiation. The results of research show the prospects of the synthesized nanodispersed luminophors LaF3:Tb3+, for use as a source of luminescent radiation in optopharmacology and photodynamic therapy of tumors in organs of cranial cavity and bone tissues. Optimization of luminescent properties of the original nanodispersed luminophors, their compositions with bioactive glass, luminescent shells in the composition of magnetosensitive NCs, as well as the technology of manufacturing of these structures will significantly allow us to improve their performance characteristics. The results of the work indicate the prospects of the synthesized structures for further research under the conditions of excitation by high-permeability “soft” X-ray radiation for use in optopharmacology and photodynamic therapy of tumors in organs of cranial cavity and bone tissues. Optimization of properties of the original nanodispersed luminophors, their compositions with bioactive glass and magnetosensitive carriers Fe3O4 will allow us to improve significantly their performance characteristics.