| Because of their unique properties, silica materials with hollow structure are studied extensively in the fields of medicine, catalysts, paper, plastics processing, paint, insulation, adiabatic, and etc. Among many preparation methods of hollow microspheres, the template method is the most popular and effective technique. Double emulsion is a composite system in which O/W and W/O emulsion could coexist. Because of its unique three-phase system, which can provide templates for hollow microspheres structure, and is easy to operate, the double emulsion template becomes a new approach for the preparation of hollow microspheres materials.In this work, double emulsions were used as a template to prepare mesoporous hollow silica microspheres for the application of sustained drug delivery. In addition, two drugs with different solubilities were encapsulated in the silica microspheres simulataneously during the preparation process to form some microcapsules, and both drugs showed well controlled release properties. The main contents are as follows:1. Double emulsions template method was used to prepare multi-hollow silica microspheres. The as-prepared materials were multi-hollow spherical particles with a diameter of5～10μm and a pore size of300nm～1μm. The structure of the microspheres could be controlled by adjusting the emulsions template.In order to solve the problem of high cost and low yield of the preparation process, the external oil phase (O2) was recycled to reduce the cost and increase productivity.2. By adopting a double templates technique, i.e., O/W/O double emulsion and polymer P123dissolved in the W phase were used as templates, respectively, macropores and silica microspheres with macro hollow cores and mesoporous structures (MMPSMs) were prepared. Model drug-Avermectin was then encapsulated into MMPSMs by an immersing method and the sustained release behaviors of Avermectin were investigated. The as-prepared MMPSMs were spherical particles with a diameter of2～10μm, a macro hollow core size of100-1000nm, a mesoporous size of4.1～4.3nm, and a surface area of232～385m2/g.The preparation method of MMPSMs was improved by adding the high-temperature aging process. Compared with the material before, the new material had better parameters and higher controlled release properties.3. By using the interfacial hydrolysis of TEOS in the water phase of an O/W/O emulsion system, the model drugs of Ibuprofen as oil-soluble drug and Vitamin C as water-soluble drug were successfully encapsulated into the hollow silica spheres simultaneously to form silica microcapsules containing both oil-soluble and water-soluble drugs. The as-prepared microcapsules are amorphous hollow spherical particles with a diameter of6～13μm. The shell is porous silica, and the two drugs were encapsulted in the pores of the shell and the inner hollow cores, respectively, by physical adsorption between the drugs and silica.Sustained release studies showed that the above-formed microcapsules had good controlled release properties for both drugs. This method can be used to encapsulate various drugs with different solubilities into materials with hollow structure in one step preparation, and to achieve sustained release for those drugs at the same time. |
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