Biomimetic Templating Synthesis And Properties Of The Micro-nanoscale Bioactive Glasses

In nature, biological systems are able to generate specifically functionalized crystalline materials with complex morphologies via the process of biomineralization that is delicately controlled by certain biomarcromolecules. Recently, controlled synthesis of inorganic and inorganic/organic hybrid materials of specific morphology, different particle size and hierarchical structure have drawn signifcant attention to the community of material sciences. In this study, bioactive glass micro-nanoscale particles with different shapes were synthesed by organic template method. The surface of micro-nanoscale particles were modified to improve the interfacial interaction between organic matrix and inorganic particles. Bone repairing materials with three dimensional porous structures were obtained with good mechanical strength. The nano-structure, bioactivity and bio-mineralization characteristics of the sol-gel derived bioactive glass and chitosan/bioactive glass (CS/BG) composite materials were investigated in detail by using XRD, SEM/EDX, FTIR, BET and DSC/TG techniques, as well as in vitro methods. The synthetic mechanism of the bioactive glass micro-nanoscale particles was also discussed.In this work, the combination of sol-gel and biomimetic organic template technologies were used to prepare micro-sized and nano-sized bioactive glass particles with different shapes and hierarchical structure. In vitro test was used to characterize the biomineralization and bioactive properties of these materials. The effects of fabrication parameters on the properties of final products, including particle size, shape, specific surface area and pore volume were studied while the shape control mechanism of bioactive glass particles was discussed. The results indicated that: (1)The dispersive state and microstructure of bioactive glass could be controlled by sol-gel technology by adding PEG as dispersant, the dispersive effect of bioactive glass was influenced by the content of PEG. Particle size, surface area and ions release behavior could be controlled and the dispersive mechanism could be explained by steric hindrance stabilization theory. PEG could adhere to the surface of bioglass particles to eliminate the interaction among particles. (2)The nano-fiber clusters of bioactive glass were successfully synthesized using sol-gel and tween-80 surfactant templating methods. These nano-fiber clusters, approximately 50~120nm in width and 200~500nm in length, were accumulated by well-ordered nano-fibers of 10nm in width. Tween-80 template in sol solution could form rod shape micelle structure, and the main driving forces for nano-clusters formation were hydroxylation reaction and hydrophilic effect. ( 3 ) Bioactive glass micro-spheres and porous micro-spheres were synthesized using ammonia and dodecylamine as catalyzer while water and ethanol were used as solvent. Technical parameters such as the speed of sample addition, reaction temperature and the ratio of starting materials, etc, were studied. In addition to catalysis, dodecylamine could also served as organic template to trigger the formation of wormlike micelle in our reaction system. The precursor of bioactive glass was reacted with micelle by hydrogen bonding and porous stucture was formed after high temperature treatment. ( 4 ) The results of in vitro test demonstrated outstanding biominerilization properties among the bioglass micro-spheres, nano-fiber clusters and nano-spheres. It further suggested that bioglass of different shapes and particle sizes exhibited great in vitro bioactivity.Bioactive glass powders were treated with phosphatidyl cholines, and the interactions between bioactive glass and phosphatidyl cholines were studied. Surface modification of bioactive glass (MBG) particles improved the interfacial interaction between bioactive glass particles and chitosan matrix, such that a uniform distribution of modified bioactive glass particles in the chitosan matrix was observed. A biomimetic porous composite was prepared from chitosan and sol-gel bioactive glass powders by freeze-drying technique. The effects of surface and component modification on the microscopic features and the compressive strength of bioactive glass were studied. The microstructure, porosity, compressvie strength and bio-mineralization characteristics of the chitosan/bioactive glass (CS/BG) composite materials were also investigated. The results suggested that the composite scaffolds were featured with highly interconnected pores with pore size ranging from 50~200μm and the overall porosity of the scaffolds was above 90%. The compressive strength of the composite could be improved by surface modification of bioactive glass.