The Bioactive Bone Tissue Engineering Research And The Preliminary Study Of The Mesoporous Hydroxyapatite

Rececntly, many advaces in engineering and material science have promoted thedevelopment of bone tisse engineering. The developments in tissue engineering materials arefrom natural materials to synthetic polymer materials and from a single material tocomposite materials and surface modification materials. The natural bone matrix is aninorganic/organic composite material, including natural polymer (collagen) and biominerals(apatite). And in the natural bone matrix the hydroxyapatite crystals, less than100nm, andcollagen fibers are closely integrated to constitue a nano-hydroxypatite/collagen composite.Therefore, the construction of inorganic/organic nanocomposites can simulate the naturalbone matrix, and promote bone repair well.As a result, the nanocomposites mimic the natural bone matrix were prepared. On theone hand, in this study the n-HA/PLGA porous composite scaffolds with different content ofn-HA were prepared by freeze-dried method. the porosity, mechanical strength, contact angleand surface morphology were characterized, moreover, and to explore the effect of differentcontent of n-HA on the porous composite scaffolds and the proliferation of osteoblasts. Onthe other hand, to some content PLGA and n-HA compound could improve the biologicalactivity of PLGA, osteoinductivity and osteoconductivity, but still not meet the need torepair the large area of bone defect. In this study, the freeze-dried method was employed toprepare the porous composite scaffolds, and the dimethyl sulfoxide, which was a cheap smallmolecule compound with biological activity and easily available, was induced into thescaffold. The effect of different content of dimethyl sulfoxide on the structure, properties andbiological behavior of porous composite scaffolds was investigated. In this study themesoporous nano-hydroxyapatite was also synthesized by low-temperature coprecipitationmethod in the presence of CTAB, and the effect of surfactant ratio on the mesoporous n-HA,and the effect of the mesoporous structure on adsorption and release of HA for BSA werepreliminary studied.1. The preparation and characterization of n-HA/PLGA porous composite scaffold byfreeze-drized for bone tissue engineering. The preliminary word studied the effect ofdifferent freezeing rate on the porous scaffolds. The results showed that the porous scaffold prepared at4℃freezeing displayed larger pores, higher porosity. Therefore, this study chose4℃as freezeding temperature to explore the effect of different n-HA content on structure,properties and cell proliferation. The porous composite scaffolds with different n-HA contentwere prepared by freeze-dried method, n-HA content was0wt.%,5wt.%,10wt.%,20wt.%and40wt.%,respectively. The porosity, mechanical strength and surface morphology ofscaffold were characterized by ethanol displacement method, electronic universal testingmanchine and scanning electron microscopy. The contact angle of n-HA and PLGAcomposite film was measured by contact angle tester. The mice preosteoblasts (MC3T3-E1)were seeded into the porous scaffolds, the proliferation was measured by MTT assay in3d,7d and14d. The results showed that the prepared scaffolds had a uniform pore distributionand interconnection. When the n-HA content was10wt.%and20wt.%, the scaffoldsdisplayed better porosity, wettability and higer mechanical strength, effectively promote theproliferation of osteoblasts.2. The preparation and characterization of MSM/HA/PLGA porous composite scaffoldwith biological activity. In our preliminary work, to some extent, PLGA and n-HAcompound could improve the biological activity of PLGA, osteoinductivity andosteoconductivity, but still not meet the need to repair the large area of bone defect.Therefore, In this study, the freeze-dried method was employed to prepare the porouscomposite scaffolds, and the dimethyl sulfoxide, which was a cheap small moleculecompound with biological activity and easily available, was induced into the scaffold. Theeffect of different content of HA on the structure, properties and cell proliferation of porousscaffold was discussed. Furthermore, the effect of different content of dimethyl sulfoxide onthe structure, properties and biological behavior of porous composite scaffolds wasinvestigated. The porosity, mechanical strength and surface morphology of scaffold werecharacterized by ethanol displacement method, electronic universal testing manchine andscanning electron microscopy. The contact angle of n-HA and PLGA composite film wasmeasured by contact angle tester. The actual content and cumulative release of MSM in theporous scaffolds were measured by inductively coupled plasma spectroscopy. The resultsshowed: the prepared scaffolds had a uniform pore distribution and interconnectivity. Whenthe MSM content was0.1%, the scaffold showed higher porosity and better mechanicalstrength. Freeze-dried method could effectively induce MSM into the scaffolds, not causingsignificant loss of the MSM, and could extend the release time of MSM.3. Cell proliferation, adhesion and osteogensis research of MSM/HA/PLGA porous composite scaffold prepared in the preliminary work. This study was to explore the effect ofthe prorous composite scaffold on osteoblasts proliferation, adhesion and bone repair. Thebiological behavior of the scaffolds were observed by MTT assay, DAPI staining andalkaline phosphatase activity determination. The scaffolds were implanted into the rabbitbone defect site, in postoperative4w and12w the materials of bone repair capacity wereevaluated due to X-ray detection of bone formation. The results showed: the MSM contentwas0.1%, the scaffold had a better osteoblast proliferation and adhesion, which couldeffectively promote bone repair.4. Preparation of mesoporous nano-hydroxyapatite using a surfactant template methodfor protein delivery. To reveal the effect of surfactant ratio on the mesoporous n-HA, and theeffect of the mesoporous structure on adsorption and release of HA for BSA. Themesoporous nano-hydroxyapatite particles were synthesized by low-temperaturecoprecipitation method in the presence of CTAB. The phase, crystal structure, chemicalstructural grops, surface morphology, the size and shape, particle size ditribusion, mesoporeparameters were characterized by X-ray diffraction, fourier transform infrared spectra, fieldemission scanning electron microscopy, transmission electron microscopy, multi-angle lightscattering detector and physical adsorption instrument. The properties of loading and releasefor proteins of samples were evaluated by BSA. The results showed: the synthesized sampleswere pure phase, low crystallinity, mesoporous nano-hydroxyapatite. When the CTAB ratiowas0.5wt.%, the samples showed better mesoporous, larger BSA loading and longer releasetime.