Preparation And Properties Of Mesoporous TiO₂、hollow TiO₂ And Its Composite

With the rapid development of materials science and modern clinical medicine,drug sustained and controlled release preparations are becoming more and more important in pharmaceutics.They can not only increase the compliance of patients,but also improve the curative effect and reduce toxic reactions.The key of drug sustained and controlled release technology lies in the choice of drug carriers.Compared with solid microspheres or other non-spherical materials,inorganic hollow microspheres have larger specific surface area,easy surface modification,special optical,electrical and mechanical properties.The internal cavity of inorganic hollow microspheres can accommodate a large number of guest molecules.The porous shell on the surface can be used as a channel for the release of guest molecules,so it has been widely studied in the field of slow and controlled release.In this paper,the preparation and properties of mesoporous TiO₂、hollow TiO₂ and hollow TiO₂/HA composite microspheres were studied.The structure was characterized by X-ray powder diffraction（XRD）、X-ray photoelectron spectroscopy（XPS）、Fourier transform infrared spectroscopy（FTIR）、Field emission scanning electron microscopy（FESEM）、Transmission electron microscopy（TEM）、Energy dispersive X-ray spectrometer（EDS）、Raman spectroscopy（Roman）and N₂ adsorption-desorption analyzer、Delsa Nano C nanoparticle size/Zeta potential analyzerand Magnetometer,in order to provide reference for the applications of TiO₂ in the field of drug controlled release and photocatalysis.The main results are as follows:Anatase TiO₂ microspheres were prepared by hydrothermal assisted homogeneous precipitation method using cheap titanium source and urea as precipitator.The effects of hydrothermal time and reaction temperature on the microstructures,crystallinity and specific surface area were investigated.The experimental results showed that the calcinedTiO₂ is anatase after hydrothermal time of 0.5 h and temperature of 120℃.The crystalline form is good,the dispersibility is good,the particle size is uniform,about 2³μm.The adsorption curve belongs to type IV isotherm and has H3 hysteresis loop.The corresponding specific surface area is 91.0629 m²·g^-1 and the pore size is about14.87 nm,which belongs to mesoporous materials.Using SiO₂ as template,hollow microspheres of TiO₂ were prepared by hydrothermal assisted hard template method.The technological process of synthesizing SiO₂ by St?ber method and the formation process of hollow TiO₂microspheres were optimized.The hollow TiO₂ was mixed with HA prepared by ultrasonic chemical method.The experimental results showed that SiO₂prepared by St?ber have good dispersibility and uniform size.The thickness of the TiO₂ shell is about 104.0±11.58 nm,the diameter of the cavity is about 240.4±17.74 nm,and has good monodispersity.The nanorod-like structure of HA shows that the surface of TiO₂ nanoparticles is successfully coated with HA.The biocompatibility of mesoporous TiO₂、hollow TiO₂ and hollow TiO₂/HA composite microspheres was studied.The experimental results showed that when the concentration of mesoporous TiO₂ is less than 2 mg/mL,the hemolysis rate of the material is less than 5%,while that of hollow TiO₂ and of hollow TiO₂/HA composite microspheres were not more than 3%,demonstrating that the latter two materials had better safety.The drug loading and entrapment efficiency of mesoporous TiO₂、hollow TiO₂ and hollow TiO₂/HA composite microspheres were studied.Used doxorubicin hydrochloride（Dox·HCl）as drug model.And their drug release behavior was analyzed to further explore their drug loading properties.The results showed that hollow TiO₂ microspheres showed highest drug loading capacity,when the drug loading ratio is 1:2,the drug loading and encapsulation efficiency of hollow TiO₂microspheres were the best compared with the other two materials（the drug loading and the encapsulation efficiency were33.12±0.01%and 99.03±0.24%,respectively）.In vitro drug release behavior of hollow TiO₂/DOX microspheres was pH-responsive,and showed a slow and constant release trend.Therefore,hollow TiO₂are more suitable as drug carrier materials.The photocatalytic activity of mesoporous TiO₂、hollow TiO₂ and hollow TiO₂/HA composite microspheres was studied using methyl orange（MO）as a pollutant model.The results show that the mesoporous TiO₂ calcined at 700℃is anatase,can efficiently degrade MO（the degradation rate reaches 99.3±0.08%in 1 h）,and then was magnetically modified to prepare photocatalysts with excellent magnetic response.For hollow TiO₂,the photocatalytic degradation rate of MO is almost 0,while reached 15%after 100 minutes treatment for hollow TiO₂/HA composite microspheres.It is concluded that anatase-type mesoporous TiO₂ is very suitable for photocatalytic applications.