Preparation And Biological Application Of Gd-Based Fluorides Multifunctional Nanocomposites

Multifunctional nanocomposites with luminescent,magnetic,and photothermal properties have gained intensive attention owing to their extensive applications in biological fields such as bioimaging and photothermal therapy.In recent years,Rare earth doped Gd-based fluorides have been proposed as new multi-mode imaging probes due to the excellent luminescence,the large atomic numbers and paramagnetic properties of Gd element.Noble metal nanomaterials and multi-walled carbon nanotubes（MWCNTs）can convert near-infrared（NIR）to heat,so they are often used as heat source to kill tumor cells.In this dissertation,the nanocomposites with luminescent,magnetic,and photothermal properties were designed by the combination of noble metal nanomaterials/MWCNTs with Gd-based fluorides,and the biological applications of the nanocomposites were studied.The details are as follows:Multifunctional MWCNTs-NaGdF₄:Yb³⁺,Er³⁺,Eu³⁺nanocomposites were synthesized by hydrothermal method using MWCNTs as photothermal conversion agents.The results showed that MWCNTs are decorated with NaGdF₄:Yb³⁺,Er³⁺,Eu³⁺nanoparticles.The as-prepared samples have green and red emissions under NIR and ultra violet（UV）radiation,respectively.Meanwhile,the obtained nanocomposites have paramagnetic property and good photothermal conversion property.MTT assays showed that the nanocomposites have good biocompatibility.In vitro assays showed that the nanocomposites have potential applications in up-conversion luminescence（UCL）imaging,computed tomography（CT）imaging and photothermal therapy.Ag@NaGdF₄:Yb³⁺,Er³⁺,Ag@BaGdF₅:Yb³⁺,Ho³⁺and Ag nanowires@NaGdF₄:Yb³⁺,Ho³⁺multifunctional core-shell nanocomposites were prepared by liquid phase method,in which the Ag nanomaterials with photothermal conversion property were used as the cores and rare earth doped Gd-based fluorides were used as the shells.The results indicated that Ag nanomaterials were coated with Gd-based fluorides.The nanocomposites exhibit paramagnetic properties and low toxicity.Under NIR laser irradiation,the nanocomposites emit green light.Moreover,the luminescence resonance energy transfer（LRET）processes occur between Ag nanomaterials and Gd-based fluorides.In vitro UCL and CT imaging studies show that the nanocomposites have excellent imaging ability.In vitro photothermal therapy studies indicate that the nanocomposites have good photothermal conversion properties and can be used as photothermal therapy agents to kill cancer cells,and they have potential applications in biological fields such as dual-mode imaging and photothermal therapy for tumor cells.