The Preparation And Biomedical Properties Of New Mesoporous Materials With Hierarchically Porous Structure

When amphiphilic block copolymers are dissolved in a solvent which is selective forone of the blocks, various micelles such as spheres, rods, vesicles,and large compound micelles could formedas a result of the association of the insoluble blocks. These micelles are widely used in the field of preparations for nanomaterials and delivery of biological drugs. In this thesis,dual-mesoporous silica spheres (DMSSs) and hollow mesoporous silica spheres (HMSSs) had been synthesized by using amphiphilic block copolymer polystyrene-block-poly (acrylic acid)(PS-b-PAA) and cationic surfactant cetyl trimethyl ammonium bromide (CTAB) as dual templates,tetraethyl orthosilicate(TEOS) as silicon source under basic conditions. Furthermore,we also prepared superparamagnetic DMSSs or HMSSs by encapsulating the magnetite nanoparticles into the large pore channels or hollow parts and investigated their applications in MR imaging and drug loading. The main contents of this thesis include the following aspects:1.Dual-mesoporous silica spheres were prepared by using PS-b-PAA and CTAB as dual templates, TEOS as silicon sourceunder basic conditions. Various experimental factors (the amount of CTAB, the length of PS or PAA blocksand so on) had been systematically investigated for the influence of morphology, pore structure and particle size of DMSSs. The results show that both increasing the length of PS blocks and reducing the length of the PAA blocks would resulted in the disappearance of large mesopores,and have a morphology transition from dual-mesoporous structure into hollow structure;furthermore, the amount ofCTAB could effective influences the thickness of the shell,we even successfully synthesized mesoporous silica spheres with one type of large mesoporous channels just by changing the amounts of CTAB.2.According to the mechanism mentioned above, PS215-n-PAA12,which have the longer PS blocks,and CTAB were uesd as dual templates, TEOS were used as silicon source,we successfully synthesized a new type of hollow mesoporous silica spheres (HMSSs).The results show that shell thickness of HMSSs can be adjusted by changing the amount of TEOS.In addition, we carried out magnetic functionalizationof HMSSs through introducing iron oxide nanoparticles into the hollow part of HMSSs; finally, we also investigated the potential application for HMSSs as a drug carrier and MR contrast agents.3.According to the similar process, we prepared superparamagnetic functionalized DMSSs with different loading of magnetite nanoparticles and investigated the relationship between loading amounts of ironand the capability of MR imaging.We found that the properties of MR imaging increased with the increase of loadingamounts of iron,and for the highest iron content of the sample, the r2relaxation values were calculated to be400mM-1·S-1which further demonstrates the great potentialsin the field of MR imaging.