| Magnetic thermo-sensitive polymer composite microspheres are new types of nanostructured material.The loading ability of magnetic thermo-sensitive polymer composite microspheres with holes can be improved due to the presence of theirs internal cavity.Because of the dual ability of thermo-sensitive and magnetic energy so that they exhibit many potential application in many fields,such as separation and purification,carriers for drug delivery and enzyme,etc.This kind of microspheres has many advantages such as rapid targeting,drug release can be controlled by temperature and can be used in magnetic hyperthermia,which makes them to be the hotspots in microspheres in the field of targeting drug delivery systemHowever,most of magnetic thermosensitive microspheres were prepared by coating thermosensitive polymer on the surface of magnetic nanoparticles.The drug release rate of thermosensitive magnetic microspheres prepared by this method is strongly influenced by the network structure of the thermo-sensitive polymer.When the temperature-sensitive polymer graft into the hollow microspheres,it can not only greatly increase the loading capacity,but decent the release rate due to the double protection of the network structure and the shell wall.In theoretically,the sustained release will be better than that microspheres with thermosensitive polymer on the surface.In previous studies,the pore size of microspheres used as carriers usually have a pore size of 2 – 3 nm which restricts the selection of drug molecule that can be loaded and their biomedical applications.However,the microspheres are easily ruptured and destroyed by constructing large,dense holes in small particles with diameter of less than 200 nm.In this context,the design of small microspheres with macroporous holes that are structurally stable enough to carry large molecular drugs is an attractive and challenging subject.The key point of preparation of thermosensitive magnetic microspheres with holes is that the hollow magnetic microspheres with holes should have good dispersibility,biocompatibility,physical and chemical stability and can be easy modified.After grafted thermosensitive polymer,the dispersibility,stability,magnetic and thermosensitive ability of magnetic thermosensitive composite microspheres shouldn't be affected.In this context,the research work of this paper is focused on the preparation,characterization and preliminary application of thermo-sensitive magnetic microspheres?P?NIPAM-AA?/Fe3O4/SiO2 microspheres and FA-P?NIPAM-AA?/Fe3O4/SiO2 Microspheres?,and their application in BSA loading and sustained release properties.The main contents and results of the study are as follows:?1?The preparation of P?NIPAM-AA?/Fe3O4/SiO2 microspheres: After Pickering and chemical etching of Fe3O4/SiO2,the p-Fe3O4/SiO2 microspheres were obtained with the diameter of 102 ±9 nm,the surface holes in the arrange of 18 nm-37 nm,the cavity about 57 nm,the thickness of SiO2 layer about 6 nm and the specific surface area about 40 m2/g.The critical temperature of P?NIPAM-AA?/Fe3O4/SiO2 composite microspheres was 42.5 °C when the mass ratio of inorganic content to organic content was 6.26 %.The saturation magnetization was 72.7 emu/g,zeta potential was-16.8 e V.?2?The loading capacity and release properties of P?NIPAM-AA?/Fe3O4/SiO2 microspherers were studied.The results showed that the loading capacity of microspheres after modified with temperature-sensitive polymer P?NIPAM-AA?was higher than that of pFe3O4/SiO2 microspheres about 120 % and the loading capacity can be up to 120 mg/g,while microspheres showed good sustained release properties.?3?In order to improve the targeting of microspheres,we graft the folic acid on the magnetic thermosensitive polymer P?NIPAM-AA?/Fe3O4/SiO2 microspheres.In this process,the folic acid was acitived by EDC and NHS,and P?NIPAM-AA?/Fe3O4/SiO2 microspheres was grafted with amide.Then the folic acid was graft to P?NIPAM-AA?/Fe3O4/SiO2 microspheres by amide reaction.The P?NIPAM-AA?/Fe3O4/SiO2 microspheres exhibit good sustained release properties of BSA. |
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