3-Dimensional Porous Scaffolds Consisted Of Hydroxyapatite Spherules And Their Induction To Ectopia Bone Gorwth In Vivo

The scaffold of bone tissue engineering as a branch of tissue engineering was got a broad study and development, it could be offer some new ideas and bring some hope for solving and improving the therapy of bone repair and replacement in people's daily life. In the study of this field, kinds of material is the key factor. A lot of study indicate that many kinds of materials can be used in bone tissue engineering, but they must have the co-characteristics: be good at biocompatibility (innocuity, no-teratogenesis, no-inflammation response etc), biodegradation (the velocity of degradation can be controlled), micro-environment of material's surface (include microporous and roughness) and mechanical property (to gratify the need of experiment). On a certain extent, function of the scaffold is influenced by its shape and structure, therefore, more and more idiographic requirements can be proposaled in the interest of improving capability of it. For instance: three-dimensional interconnection, high porosity and specific surface area, pore size and distribution, can be controlled and repeated easily. In order to satisfy this requirements many methods of fabrication scaffold were used in practice, but, up to now, people are much to seek a sort of preparation method which is simpleness and economy. At beginning of this, we put up a exploring experiment in this paper.Hydroxyapatite (HA) belongs to bioceramic is performed in this study because its chemical composition and crystal structure is extraordinary similar with inorganic in dens and osseous tissue in vertebrate, which with excellent biocompatibility and combine with osseous tissue easily. A novel porous bioceramic scaffold is prepared by accumulating HA spherules and in order to study ectopia osteoinduction of the scaffolds in vivo which were implanted in four different non-osseous sites in dogs. At last, we get a useful and satisfying results, the main conclusions are drawn as follows:1. Fabrication porous HA spherule by the method of sol-gel and water/oil emulsification technology. Results of characterization reveal that: porous HA spherules with a high specific surface area, a appropriate mechanical property and excellent sophericity, pores size is inverese ratio to stirring speed and porosity of HA spherule in the scope of 15% to 20%, micropores size and shape can be changed by pore-maker, under this conditions, porosity of HA spherules can be arrived at 30% in max.2. Method of polymer sponge template is used to preparation porous HA tube and discs, and a novel three-dimensional porous bioceramic scaffold called the HA spherule scaffold with regular shape, excellent interconnection and high porosity (average is in the scope of 48% to 66.9%, the max. can be up to 70%) manufactured by accumulating HA spherules. The great advantages of this scaffold are the controlled interconnection of pores, the adjustable microstructure of HA spherules and the easy reconstruction of porous structure.3. To study a ability of osteoinduction of the scaffolds which were implanted in four different non-osseous sites in dogs: in abdominal cavity (AC), peritoneum pocket (P), muscle (M) and beside the femur (FP). Samples are collected after six months and the results indicate that: the HA spherule scaffold can induce angiogenesis and bone formation without use of cytokines for vasculogenesis or bone-induction. There were not only a mass of blood vessels appeared and a lot of mature osteocytes inlayed on the bone lacuna but also the bone stroma grew well and a plenty of collagen fibres filled in it appeared around the spherules while speciments implanteded in P and M, and when the speciments in FP the growth conditions is the best that the osseous tissues developed quite perfect and the newly-formed bone even had a lamellar structure with many mature osteocytes. So, these proved that this scaffold have a reasonable pore structure, pore size and porosity, which in favor of attachment, differentiation and proliferation of cells, provide a convenient channels to transport tissue fluid and nutrient, speed up metabolism. In contrast, there were a small quantity of blood vessels and almost no newly formed bone in the specimens implanted in abdominal cavity while a few of collagen fibres around HA spherules. Different results reveal that ectopia osteoinduction is directly attached to the site of non-osseous and the degree of vascularization in prophase is a vital importance to osteoinduction. In this study, the sequence of osteoinduction ability at the four different non-osseous as follows: FP > P = M > AC.