Synthesis Of Hierarchical And Flower-like TiO₂ Nanowire Microspheres As Biocompatible Cell Carriers

Microspheres have been extensively applied as the commonly used injectable cell carriers because of their high surface area and good flow ability as well as well-defined spherical morphology.However,the current microspheres normally have dense or porous structures and lack the fibrous structure of the extracellular matrix to enhance cell-material interaction.Nanowires are one type of the fibrous materials.They could not only be used as targeted transport carriers,but also transmit biological information.Titanium dioxide(TiO₂)nanowires are one type of the representative TiO₂ materials and could be easily synthesized via the hydrothermal route.Silk fibroin has good biocompatibility,aqueous solution stability and mechanical properties,and is widely used in the field of biomedicine.Taking the advantages of both TiO₂ nanowires and silk fibroin,in this study,TiO₂ nanowire microsphere with a hierarchical structure is firstly synthesized through a simple hydrothermal method and then functionalized with silk fibroin for enhancing biocompatibility.This research mainly includes the following three aspects.(1)Preparation and characterization of TiO₂ nanowiresTiO₂ nanoparticles were firstly prepared from isopropyl titanate as titanium source by sol-gel method route and then hydrothermally treated in the Na OH solution to produce TiO₂nanowires.The morphology analysis shows that TiO₂ nanoparticles were in situ converted to TiO₂ nanowires under alkali hydrothermal condition.The as-synthesized TiO₂ nanowires had a diameter of 10-20 nm.(2)Preparation and characterization of TiO₂ nanowire microspheres with hierarchical structureTiO₂ nanowire microspheres were synthesized by hydrothermal treatment of TiO₂nanoparticle microspheres in the Na OH solution.Gelatin/TiO₂ nanoparticle composite microspheres were prepared using gelatin and TiO₂ nanoparticles as raw materials by emulsification method and then calcined to prepare TiO₂nanoparticle microspheres.After hydrothermally treated in Na OH solution,TiO₂ nanoparticle microspheres were in situ converted to TiO₂ nanowire microspheres.Morphological analysis and elemental analysis indicate that TiO₂ nanowire microspheres were spherical in shape and had a diameter of around550?m.They showed a hierarchical and flower-like structure and their surface was composed of many nanowires with the diameter of 10-20 nm.They were mainly composed of C,O,and Ti elements and constructed by both rutile phase and anatase phase.(3)Surface modification and biocompatibility evaluation of TiO₂ nanowire microspheresTiO₂ nanowire microspheres were further functionalized with silk fibroin.Biological evaluation was evaluated by culturing the as-synthesized microspheres with fibroblast L929cells.Cell viability was evaluated via the conventional MTT assay and Live/dead cell staining method,while cell morphology was observed with a SEM machine.The results showed that TiO₂ nanowire microspheres favored cell attachment and proliferation and showed a good biocompatibility.The decoration of silk fibroin on TiO₂ nanowire microspheres enhanced the cell biocompatibility.