Preparation, Surface Modification And Biological Application Of NaYF₄ Matrix Nanoparticles

Rare earth doped nanomaterials have unique optical and magnetic properties and many advantages:easy preparation,controllable size,easy surface modification and less cytotoxicity.And they are used in biological detection,biolabelling and bio-imaging as tracing materials.As doped nanoparticles have the functions of upconversion luminescence and magnetism,they can be used as dual modality imaging agents and have high sensitivity and resolution,which are useful in disease diagnosis and theranostic.Gene therapy is to transport purpose genes into target cells to cure immunological diseases,hereditary diseases and malignant tumor,the key of which is to choose proper gene vectors and the lanthanide-doped nanoparticles is used as a tracer for gene carrier.Here,we prepared and modified lanthanide-doped NaYF4 nanoparticles to fabricate a novel gene vector and multi-modal contrast agent,which have the potential in gene theranostic and bio-imaging.In this paper,NaYF4:20%Yb3+,2%Er3+ nanoparticles were synthesized by solvothermal method and characterized by polycrystalline powder X-ray diffraction(XRD),transmission electron microscopy(TEM),Dynamic Light Scattering(DLS),high resolution transmission electron microscopy(HRTEM)and fluorescence emission spectra.The results showed the nanoparticles had uniform size,high crystallinity,hexagonal β phase and well-defined luminescence spectra excited under 980 nm.The nanoparticles were multilayer modified by ligand exchange and electrostatic layer by layer self-assembly.After optimization of reaction conditions,the nanomaterials with different charge on the surface were prepared.The nanoparticles with polyethylene imine(PEI)on the outmost layer have certain buffer capacity and good stability under physiological condition.The modified NaYF4:Yb,Er nanoparticles were then combined with DNA to construct a novel Non-viral gene vector and the results showed that this vector has little cytotoxicity in LO2 cells and good stability under physiological condition,indicating the potential in gene therapy.Then we further investigated the biotoxicity and upconversion luminescence(UCL)and magnetic resonance(MR)multimodal imaging of the NaYF4:Yb3+,Tm3+,Co2+@OCC upconversion nanomaterials prepared by our group.By incubating the nanoparticlels with HepG-2 cells to evaluate the live cell toxicity,we found that the prepared nanoparticles also have the ability of UCL imaging in live HepG-2 cells.Nanoparticles were then injected into mice in vivo experiments and the results showed that the nanoparticles have low cytotoxicity by histological diagnosis.At last,the nanoparticles were injected into live mice to investigate UCL and MR imaging and we found that they could be applied as a high-performance dual contrast agent for both UCL and T2-weighted MR dual-modality imaging.