Hydrogen Peroxide Responsive Microcapsules Based On Boron-carbon Bond Preparation And Performance Characterization

As an important component of intracellular reactive oxygen species,hydrogen peroxide（H₂O₂）is involved in many important physiological and pathological activities,and plays an important role in inducing oxidative stress response,cell signal transduction,proliferation and differentiation.Excess H₂O₂ is produced in the body when people suffer from diseases such as cancer,diabetes and arteriosclerosis.Therefore,in view of the changes in the concentration of H₂O₂ in the human microenvironment,the development of drug carriers that are stimulus-responsive and targeted to H₂O₂ has important research significance.Microcapsule is a kind of microcontainer with core-shell structure,which has the advantages of high permeability and good stability.Drug microcapsules can encapsulate drugs without changing the properties of the drugs,and are widely used in the field of drug-loaded release,which can achieve targeted drug delivery,reduce toxicity,and improve drug utilization.In this paper,based on the H₂O₂sensitivity of boron-carbon bond,drug microcapsules with H₂O₂ stimulation response were designed and synthesized,and the performance of microcapsules was studied in detail.The main research contents are as follows:Chapter 1:This chapter briefly introduces the research progress of hydrogen peroxide stimulation-responsive materials and microcapsules,and proposes the research objectives of this paper.Chapter 2:The cross-linked starch-phenyldiboric acid drug microcapsule was prepared by reverse phase emulsion polymerization,using compressible starch and 1,4-phenyldiboric acid as wall materials and pentoxifylline as core materials.The effects of compound emulsifier ratio,emulsifier dosage,emulsifying speed,emulsifying time,core-wall ratio,wall-material ratio,reaction temperature and reaction time on the particle size,distribution and morphology of microcapsules were investigated.The structure,particle size,particle size distribution and morphology of the prepared microcapsules were characterized by infrared spectrometer,Malvern laser particle size analyzer,scanning electron microscope and transmission electron microscope.The optimum conditions for preparing crosslinked starch-phenyldiboric acid drug microcapsules were determined.Chapter 3:The coating rate of cross-linked starch-benzenediboronic acid drug microcapsules,the H₂O₂ responsive drug release performance and the drug release performance affected by the main factors were studied,and the UV-visible spectrophotometer was used for characterization.The drug release properties of the microcapsules under different H₂O₂concentrations was studied,and it was confirmed that the microcapsules had obvious H₂O₂responsiveness.It was determined that the appropriate H₂O₂ concentration for microcapsule drug release was 0.2mmol/L.Chapter 4:The cross-linked polyvinyl alcohol（PVA）-phenyldiboric acid drug microcapsules were prepared by reverse phase emulsion polymerization,using PVA and 1,4-phenyldiboric acid as wall materials and pentoxifylline as core materials.The release performance of the microcapsules under different H₂O₂ concentrations was studied,the H₂O₂responsiveness of the microcapsules was confirmed,and the appropriate H₂O₂ concentration for the release of the microcapsule drugs was determined to be 1.0 mmol/L.The influence of factors such as PVA concentration,emulsifier dosage,emulsification speed,emulsification time,core-to-wall ratio and wall-to-wall ratio on the particle size and distribution,coating rate and morphology of microcapsules was systematically studied.Infrared spectrometer,Malvern laser particle size analyzer,scanning electron microscope,transmission electron microscope and ultraviolet-visible spectrophotometer were used to characterize the structure,particle size and distribution,morphology,coating rate and drug release properties of the prepared microcapsules,The optimal conditions for preparing cross-linked polyvinyl alcohol（PVA）-benzenediboronic acid drug microcapsules were determined.