Papers by Author: C.Y. Bao

Abstract: This study was aimed to estimate the cell-activity after culture of the cell-material composite and to evaluate the feasibility of constructing tissue-engineered bone using this novel material. Hollow HA mcirospheres (H-HAMs), porous PLA\HA tube，polyurethane plunger were prepared respectively. Mesenchymal stem cells (MSCs), which were derived from rat bone marrow were utilized as seed cells.Two different methods were used to integrate the seed cells and scaffold materials. Group A: H-HAMs were filled into porous HA tube, and porous polyurethane plungers were used to cover onto the ends of HA/PLA tubes as a whole, Then MSCs were cultured on the composite scaffolds; Group B: MSCs were compounded with H-HAMs completely first, then the pre-seeded composite of H-HAMs and cells was put into the porous PLA\HA tube which was then sealed with the polyurethane plunger. 1,3,5,7 and 9 days after cell-material composites were cultured, the growing status and adhesions of seed cells were observed. The viability of cells was quantified and increased over time in different methods, but was significantly higher in Group B after 9 days of culture. SEM detection revealed that more cells were detected on the PLA\HA tube and the outer layer of H-HAMs; growth of cells was more widespread and more cells were detected on H-HAMs in Group B. However, cells on H-HAMs seem to diminish over time in both groups. As a novel 3-D Hydroxyapatite scaffold, its H-HAMs are more easy to be integrated with seed cells, to be shaped according to clinical needs because of its semi-liquidity. However, the growth of cells especially in the inner core of the integrated material needs further research.

Abstract: The purpose of this study was to evaluate the cytotoxicity of nanometer magnetic composite via being cultured with osteoblast-like cells (MG-63). The osteoblast-like cell (MG-63) was utilized as the seed cell. The cells were cultured on the surface of nanometer magnetic composite. After union culturing, on the day 1, 3, 5, 7, the cytotoxicity of nanometer magnetic composite was evaluated by MTT method and the cell morphology was observed by SEM. Meanwhile, on the day 4, 7, 10, the alkaline phosphatase (ALP) activity was tested respectively. These results demonstrated that the typical cell morphology could be observed when the osteoblast-like cells were cultured on nanometer magnetic composite substrate in vitro. Cell proliferation and ALP activity became higher as the prolongation of cultivate time in the group of nanometer magnetic composite. The study showed that nanometer magnetic composite had a little inhibition to cell proliferation and ALP activity in vitro cell culture, as compared with the chitin and PLA fiber substrate. So the feasibility of nanometer magnetic composite as scaffold for bone tissue engineering should be studied further.

Abstract: In order to modify the biological properties of pure hydroxyapatite (HAp), two kinds of zinc-containing HAp, which had zinc content of 5.10wt% and 2.54wt%, respectively, were synthesized via sol-gel technique. The obtained coatings were characterized by X-ray diffraction (XRD) and scanning electron microscope (SEM). Then the antibacterial effects were evaluated through bacteriostatic test on Streptococcus mutans (S.mutans) in vitro and zinc ions releasing ability was investigated through detecting the zinc ions concentration by inductively coupled plasma-atomic emission spectroscopy (ICP-AES). The obtained coatings were observed to possess typical apatite peaks in XRD patterns and high homogeneous and porous surfaces in SEM morphology. The coating layer demonstrated good releasing ability in Brain Heart Infusion (BHI) liquid and obviously inhibitory effects to the growth and proliferation of S. mutans. Based on the results obtained above, it is concluded that the sol-gel derived zinc-containing hydroxyapatite could be applied as an antibacterial effective biomaterial.

Abstract: The study is aimed at to explore the construction of bone graft with calcium phosphate ceramics implanted in subcutaneous fat, and provide applying technique for the in vivo bone tissue engineering. Forty-eight calcium phosphate ceramics (Ca-P ceramics) columns with Φ 5×8 mm were prepared, and eight dogs were used in this experiment. Six samples were implanted in each dog. Three in dorsal muscles while the others in subcutaneous fat. The specimens were harvested at 4, 6, 12 and 24 weeks post operation, for gross observation, SPECT and histological studies. The osseous or osteoid tissue formation at different times in the two non-osseous sites was compared and the new bone grafts in subcutaneous fat and intramuscular implantations were evaluated. The results demonstrated that the bone graft could be constructed not only in muscle but also in subcutaneous fat. Compared to that in muscle, constructing bone graft in subcutaneous fat could have brighter prospect to clinical application.

Abstract: The purpose of this study is to explore the osteoinductivity of the composite materials (calcium phosphate ceramics/PLA or collagen composites) with similar physical character of osteoinductive calcium phosphate ceramics and the influence of the chemical composition of the composite materials on osteoinductivity, and also to provide an experimental evidence for optimizing the design of the composite materials. Two kinds of composite materials were prepared. One (BCP/PLA) is fabricated with different ratio of BCP (biphasic calcium phosphate) ceramics powder and PDLLA powder through the particulateleaching technique. The other (BCP/collagen) is that BCP ceramics sintered at 1250oC and modified with collagen. The porous materials cylinders with Φ 5×8 mm were prepared. SEM was used to observe the microstructure and physical morphology of the composite materials. The two groups of composite materials cylinders were implanted in the dorsal muscles of four dogs. Six samples of each group were implanted in each dog respectively. The specimens were harvested at 2, 4, 12 and 24 weeks post operation, and thin decalcified sections were prepared for light microscopy (LM) analysis to evaluate their osteoinductivity and compare the capability of osteoinduction. The fibro-tissue and bone-like tissue were observed in the two composites, but no obvious bone formation was found in the tested periods. The results indicated that the composite materials could modify the mechanical property of ceramics. However, if the composite materials were biodegraded soon, new bone could not form into the scaffold, and the calcium phosphate should be the major component of osteoinductive materials.

Abstract: The aim of this study is to evaluate treatment effects of novel GBR membranes (PDLLA membranes) applied to bony defects around dental implants on new bone regeneration alone or in combination with bioceramic bone graft (BIO-OSS®) on the mongrel dog model in comparison with collagen membrane (BIO-GIDE®) and therefore to assess the clinical values of the novel GBR membranes and bioceramic bone graft material in dental implantology. 6 implants were placed in bilateral mandibular of each mongrel dog after preparation of mid- crestal defects. The defects on one side were covered with PDLLA membranes alone or with bone graft, while the contra-lateral sides received collagen membranes alone or with bone graft. These animals were sacrificed at 2, 4, 8,12 weeks post the GBR-operation. And gross sample examination, standardized radiographs, 99mTc-MDP SPECT and histomorphometric analysis were taken. All examinations showed similar amounts of newly formed bone beneath both types of barriers. The PDLLA or collagen membrane with bone graft groups showed better results than the membrane used alone groups. The results indicated that PDLLA membranes especially with bioceramic bone graft presented an improved response in dealing with bony defects around implants.

Abstract: Circumambient tissues infection is a common complication of implanted percutaneous and permucosal devices (PDs). In order to counter the infection, the titanium abutment surface of PDs was modified to achieve antibacterial and antiadhesive activities. Titanium discs were immersed into hydroxyapatite (HA) sol containing different mass fraction silver and thermally treated to get modified discs. The modified discs become more smoother and get crystal HA coatings containing silver. Silver ion release test demonstrate the release rate is very slow and the coating is a reservoir of silver. The antibacterial and antiadhesive effects of modified discs on Staphylococcus aureus and Porphyromonas gingivalis were evaluated. Modified titanium discs with silver significantly inhibited the growth of these two bacteria compared with both the polished titanium discs control and modified titanium discs without silver. And titanium discs modified with more silver have higher antibacterial activity and less bacteria adhesion in this study. These findings indicate that titanium surface modified with the HA sol-gel containing silver could achieve antibacterial and antiadhesive activities, and the abutments of PDs are promising to be modified by this method.

Abstract: The purpose of this study was to explore the feasibility of repairing massive bone defect with in vivo tissue engineering(TE) bone, and to provide experimental evidence for the application of in vivo TE bone into clinic in the future. Six calcium phosphate ceramics (Ca-P ceramics) columns were prepared, and then immersed in dynamic revised simulated body fluid (RSBF). 72 hours later, the bone-like apatite was formed on the surface and pore walls of ceramics. Three dogs were used in this study. Two ceramic columns were implanted bilaterally in the femoral muscles of each dog to construct living bone graft of in vivo TE bone. 6 weeks after implantation, they were transplanted to the box-like bone defects sites created in bilateral mandible of the same animals. The dogs were sacrificed at 8, 12 week after operation respectively. Samples were harvested for gross observation, X-ray examination, tetracycline fluorescence labeling, SPECT and histological observation. These results demonstrated that as a living bone graft, in vivo TE bone participated in the bone metabolism of host, and integrated with the host bone. It is feasible to reconstruct box-like bone defect of mandible with the in vivo TE bone.

Abstract: The purpose of this study was to develop a feasible approach for repairing periodontal bone defects with the in vivo tissue engineering bone incorporated with bioabsorbable PLA membrane and to provide evidences for the clinical application. Osteoinductive HA/β-TCP sintered at 1100°C were implanted in the femur medial muscles in the hind legs of three dogs. Four weeks after implantation, the in vivo tissue engineering (TE) bone was explanted. Meanwhile, artificial periodontal bone defects of 8mm×6mm were performed on the buccal side of 4th premolar and 1st molar of mandible bilaterally, with the exposure of dental roots. The defects were treated as follows: (1) in vivo TE bone and PLA membrane; (2) HA/β-TCP ceramics and PLA membrane; (3) PLA membrane only; (4) empty control. At the 2, 4, 8 weeks post-transplantation, the dogs were sacrificed. The specimen were harvested and evaluated by gross inspection, dental radiography, SPECT (99mTC-MDP) and histological observation by MPIA2500. The results showed that more mature osseointegration was found in the group 1. We presumed that the in vivo TE bone graft could enhance the reparation of periodontal bone defects.

Abstract: Calcium phosphate (Ca-P) biomaterials have been proved to show osteoinductivity, however the affecting factors and mechanism are still unclear now. In this study, the surface characteristics of biphasic Ca-P ceramics (hydroxyapatite/tricalcium phosphate; HA/TCP) sintered at the distinct temperature were investigated and the mechanism of the osteoinductivity was discussed. The osteoinductivity of HA/TCP ceramics increased with decreasing the sintering temperature. The different surface micro-structure resulted from different sintering temperature includes phase composition, surface micro-structure, and surface potential. These characteristics should be the important factors affecting osteoinductivity.