Papers by Author: Guo Min Ou

Abstract: A polyelectrolyte complex (PEC) composed of chitosan (CS) and phosphorylated chitosan (PCS) was used to encapsulate a calcium phosphate by a biomimetic method. An acidic CS (polycation) solution containing calcium and phosphate ions (Ca2+: 6mM, Ca/P = 1.67) was added into PCS (polyanion) solution leading to the formation of a polyelectrolyte complex (PEC) with nanoscopic carbonate-containing, low-crystallinity hydroxyapatite (HA) distributed evenly in the fibrils of the PEC by controlled crystal growth. The resulting composite material, PEC-HA, has a complicated, hierarchical porous structure that is expected to have high bio-compatibity and that may be of use as a carrier for controlled-release therapetic agents.

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 evaluate the response of osteoblasts to calcium phosphate with different surface modification, and to evaluate the osteoinductive capabilities of these biomaterials. 60HA/40α-TCP ceramics sintered at 1250oC was applied in this study. A ceramic cylinder with F5mm×8mm and slice with F10mm×1mm were prepared respectively. One third of the ceramics was used to form bone-like apatite (BLA), and the surface of another one third was modified with collagen. Osteoblasts (1×106/ml) were co-cultured with the three kinds of thin slices for 12h, 24h and 48h. SEM observation was applied to evaluate whether the surface modification and BLA formation could affect the attachment and proliferation of osteoblast in vitro. The three kinds of cylinder samples were implanted in dog muscle to evaluate their differences in osteoinduction. Cells grew in multi-layers and attached to the surface and proliferated well in the collagen and HA/TCP group. In the untreated and BLA precipitated groups, cells did not attach to the surface well. Osteoinduction was good in the BLA precipitated group and the amount of bone formed was higher; in the untreated group and collagen-treated group, no bone formation was observed in the tested period. This result indicated that the scaffold used in cell-materials composites in vitro and that in osteoinductive material based tissue engineering in vivo was not same.

Abstract: A novel three-dimensional scaffold of hydroxyapatite(HA)-polyelectrolyte complex (PEC) composite hydrogel was synthesized by a biomimetic method. PEC hydrogel was formed from equal volumes of 1% phosphorylated chitosan in water and 1% chitosan in 1% acetic acid solution. This PEC hydrogel was soaked in saturated Ca(OH)2 solution for 4 d and then in accelerated calcification solution (ACS) for 7 d, both at 37 oC. The PEC hydrogel was a nano-composite material with multiple levels of hierarchical porosity; hydroxyapatite (HA) crystals nucleated and grew on the fiber surfaces of the hydrogel; Rat osteoblasts were then seeded in this three-dimensional scaffold of HA-PEC composite hydrogel, the three-dimensional scaffold of HA-PEC hydrogel revealed excellent biocompatibility.