Fabrication And Characterization Of Porous Calcium Carbonate Bioceramic Scaffolds

With the development of bone tissue engineering (BTE), it can provide a newmethod to reconstruct organ damage or defect due to the birth deficiency, accident andso on. Scaffolds play a key role in bone tissue engineering, which serves as a templatefor cell interactions and the formation of bone-extracellular matrix to providestructural support to the newly formed tissues. Corals have been used for repairingbone defects due to their biocompatibility, high mechanical strength and structurewhich are similar to cancellar bones. However, a widely use of corals for orthopaedicapplication has been limited by their supply difficulty, biological variability and viralor bacterial contamination risk. It is feasible to replace coral with synthetic calciumcarbonate ceramics in order to avoid the contaminants and biological variability innatural corals. Calcium carbonate which is the major component of coral had beenshown with good biocompatibility and osteoconductivity. In this thesis, calciumcarbonate (CaCO3) ceramic scaffolds were prepared via sintering the cylindricalspecimens that were formed by pressing bicarbonate (Ca(HCO3)2) and pore-formingagents in a stainless steel cylinder mould. Furthermore we use the β-Ca2SiO4toimprove the mechanical property and bioactivity of these scaffolds. Results obtainedfrom this work are described as follows：(1) The bulk calcium carbonate ceramic was prepared by compacted pureCa(HCO3)2powders. After sintering at550°C, the ceramic exhibit the maximumcompressive strength of39.3MPa. X-ray diffraction (XRD) analysis of the resultingporous calcium carbonate ceramic confirmed the material to be pure calcite (CaCO3).The porous scaffolds were prepared by using fibers that were radom mixed orpre-fixed as pore-forming agents. It can produce scaffolds with different porosities bycontrolling the dosage and arrangement of adding fibers. The scaffolds are preparedwith interconnected network and good biocompatibility.(2) Porous materials were prepared by adding NH4HCO3powder as pore-formingagents. The prepared scaffold had appropriate compressive strength and porosity.Scanning electron microscopy (SEM) revealed small chambers, likely to have beengenerated through NH4HCO3decomposition and interconnected pores. The porenetwork combined with the cytocompatibility of calcite enables the attachment andproliferation of MG-63cells. The cells exhibit a healthy polygonal appearance on both the exterior and interior surface of the samples. These results demonstrated thatthe prepared porous calcium carbonate ceramic scaffolds displayed goodbiocompatibility.(3) Using β-Ca2SiO4ceramic particles to improve the compressive strength andbioactivity of CaCO3ceramics. The β-Ca2SiO4/CaCO3composite scaffold wereprepared by mixing Ca(HCO3)2and β-Ca2SiO4ceramic particles which werefabricated by sol-gel method. It was found that by adding β-Ca2SiO4ceramic particlecan improve the compressive strength of the scaffolds significa ntly. The resultsobtained from the SBF soaking test showed that these ceramics can induce thedeposition of hydroxyapatite on their surface. Furthermore, compare to pure CaCO3scaffolds, β-Ca2SiO4/CaCO3composite scaffold induce hydroxyapatite depositionmore rapaidly and the structure of hydroxyapatite deposition exhibit denser. The SEMimages observed after culturing MG-63cells on the scaffolds showed that addingβ-Ca2SiO4particles can promote the adhesion of cells, and the β-Ca2SiO4/CaCO3composite scaffold also had good biocompatiblility.From the results described above, it can be seen that this new calcium carbonateceramics can be potentially used in the bone tissue engineering.