Synthesis, Modification And Biomedical Application Of Upconversion Fluorescent Nanocrystals

Upconversion luminescence nanomaterials have great potential in biomedical field duo to their unique optical properties. But their applications are still relatively limited due to the as-syhthesized upconversion luminescence nanomaterials are hydrophobic and no biocompatibility. To solve this problem, surface modifications and functionalization of the as-prepared hydrophobic NaYF4:Yb,Er nanocrystals were studies in this thesis, and we developed two kinds of nanocomposite materials with targeting and good biocompatibility for targeted imaging and treatment of tumor cells. The main research works are as follows.(1)Monodisperse, oil-dispersible hexagonal-phase NaYF4:Yb,Er nanocrystals were synthesized via a high-temperature organic solvent method. Then, surface modifications of the as-prepared hydrophobic NaYF4:Yb,Er nanocrystals were carried out using a ligand exchange mothod, the 2,3-dimercaptosuccinic acid functionalized NaYF4:Yb,Er nanoparticle were obtained; (2) The amine groups of chitosan-FA conjugate were reacted covalently with the carboxyl groups located on the surface of NaYF4:Yb,Er nanoparticles. A kind of NaYF4:Yb,Er@chitosan-FA nanocomposite materials with targeting and good biocompatibility were developed. Meanwhile, cell imaging demonstrated that the NaYF4:Yb,Er nanoparticles functionalized with chitosan-FA conjugate were specific in targeting lung cancer cell lines overexpressing the folate receptor (H460) in comparison with normal cells (HLF). (3) The carboxyl groups functionalized NaYF4:Yb,Er nanoparticles and folic acid were conjugated covalently to the surface of multiwalled carbon nanotubes via an amide bond to form NaYF4:Yb,Er-MWCNT-FA nanocompounds. The results of confocal laser scanning microscopy based on the functionalized nanomaterials, demonstrated a high effectiveness to detect cancerous cell lines overexpressing the folate receptor (Hela cell) from normal cells (HLF cell) by tracing the fluorescence imaging with high fidelity. Further, DOX was successfully loaded to the prepared NaYF4:Yb,Er-MWCNT-FA nanomaterials mainly through noncovalentπ-πinteractions to achieve targeted diagnosis and therapy of tumor cell simultaneously.