Fabrication And Properties Of The Novel Micro-nanoscale Bioactive Glasses

Micro/nano biological material has become the research hotspot and difficulty in the field of biomedical materials. A number of studies have shown that micro/nano structure of biological material can show a positive biological response such as greatly promoting cell adhesion, proliferation and differentiation, comparing with other biological materials. Bioactive glass (BG) possesses the similar chemical composition with the bone and teeth, and has the high apatite-forming bioactivity, biocompatibility, bone conductivity and inductivity. BG is the ideal biomaterial for bone tissue regeneration. However, for the traditional BG preparing by high temperature melting conditions it is difficult to control the structure and this material has the low biological activity and poor degradation. Sol-gel derived bioactive glass possesses lot of advantages such as mild conditions, controlled composition and design, high bioactivity and degradation. The problems for sol-gel BG are that it is difficult to control the dispersion, micro/nano structure, shape and size of BG particle. This study will use sol-gel method combining biological organic templates and colloidal chemistry, to control and design micro/nano structure of bioactive glasses, to study forming mechanism of micro/nano structure and their physical and chemical properties, apatite-forming bioactivity. The biological evaluation of material was carried out using marrow stem cell (MSCs) as a model. Main research work and conclusions are as follows:(1) Micro-nanoscale surface control and properties of sol-gel bioactive glass particlesIn sol-gel preparation process, by the hydroxyl bone interactions between hydroxyl-carboxyl acids and bioactive glass sol particles, we successfully controlled the formation of micro/nano surface structure of sol-gel bioactive glass particles.By changing concentrations of organic acids, the surface area, pore volume and mesoporous size can be controlled in between 80-200 m2 / g, 0.1-0.5 cc/g and 2-60 nm, respectively. The ions release behavior are according to the first order kinetic model. Ions release has little effect on the pH of environment. The ions release ratios and HA forming are controlled by surface properties of particles. The micro-nanoscale surface and high ions release can induce the fast HA forming ability. For cell culture of dispersive particles, lower surface area and slow ion release rate of materials are helpful to promote cell proliferation. For the cells culture of bulk particle surface, materials with the micro/nano surface structure and high surface area can enhance cells proliferation and differentiation.(2) Micro-nanoscale morphological control and properties of sol-gel bioactive glass particles For this study, through sol-gel co-organic template technology and optimizing process parameters, we successfully controlled the morphology of sol-gel bioactive glass particles. Regularly spherical bioactive glasses (SBG) can be prepared using PEG as templates (mean size 4.5μm). Tuning the adding of templates and sintering temperature can induce the formation of hollowly spherical bioactive glasses (HSBG) and porous sol-gel bioactive glasses particles (PBG). RBG can be prepared by increasing the template concentration.The study of short-term ion release behavior showed that SBG greatly reduces the ion release speed of BG and makes the whole ion release speed more uniform; SBG possesses the slower HA forming rate than irregular BG; SBG can induce the formation of uniform nanometer fiber sheets of apatite crystals; The apatite crystals grow along the direction (002); SBG (regular morphology) can significantly improve cell proliferation and adhesion.In this study, by sol-gel method and template hydro-thermal process, a three dimensional porous bioactive glass bulk (3D-PBG) with strength was synthesized. 3DPBG has the multi-level pore distributions(10nm-10μm) and nanoscale pore wall. The size of pore wall, pore size, pore morphology and the compressive strength can be controlled by tuning the parameters in detail. Because of the 3D connected pore distributions, 3DPBG presents the high HA forming ability and cellular compatibility.(3)Micro-nanoscale size control and properties of sol-gel bioactive glass particlesIn this study, controlled micro-nanoscale bioactive glass particles (NBG) can be prepared successfully by template-acids-catalyzed sol-gel technology and sols-basic precipitation method. The forming mechanism of nanoscale particles can be explained by sol-gel-template interaction. By sol-gel co-template method, the particle size of NBG can be controlled at 70 nm-5μm; Adjusting the volume ratio of water and TEOS can control the particles size of 500 nm-2μm; By sol-basic precipitation method, NBG sizes are about 40-350 nm by adjusting basic concentration and about 20-100 nm by regulating the PEG weight.Two stages of ions release can be found for NBG: higher release speed than BG at early time (6h) and stable release at middle or later time; NBG possesses the fast HA-forming ability and well crystalline dense HA layer formed after reaction for 6 h; Better cells attachment on NBG than BG can be found at early time and NBG promoted the cells proliferation.