Papers by Author: Wei Qi Yan

Abstract: In the present investigation, four titanium (Ti) surfaces of dental implants were compared through in vitro systems. The surface roughness of Ti was measured by TR240 mobile surface roughmeter. The Ti implants were seeded with human periodontal ligament cells (hPLDCs) and maintained for a period of 0-7 days. The adhesion, proliferation, and differentiation of hPLDCs were observed by using Cell morphology, cell counting and Osteocalcin (OC) immunofluorescent staining. Results suggest that surface roughness of titanium favors hPDLCs behavior and improves cell adhesion, proliferation, and differentiation.

Abstract: For dental/orthopedic implants to achieve better bone apposition and bone-implant bonding, various approaches to improve titanium surfaces have been developed. Recently, a fluoridated hydroxyapatite (FHA) coating on titanium (Ti) implants was made by sol–gel method and shown to be a possible applicative bone implant. The purpose of the current study was to evaluate biological responses and biomechanical bonding strength of FHA coated Ti implants as compared with that of the conventional Ti alloys and hydroxyapatite (HA) coated Ti implants. In vitro assays were made using human osteoblast-like cell (MG63) culture on different implants with cell attachment, morphology and differentiation evaluations. The implant plates were also implanted into the proximal metaphysis of New Zealand White rabbit tibiae. After 8 and 16 weeks implantation, mechanical and histological assessments were performed to evaluate biomechanical and biological behavior in vivo. The results showed that the cell adhesion and cell growth rate on the FHA and HA surface was higher than that on cp Ti surface (p<0.01), and insignificant difference was observed between two coated groups. Mechanical test demonstrated that the FHA implants had a higher interface shear strength than the both controls at 8 and 16 wks, with no significant difference with HA-Ti. Histologically, the coated implants revealed a significantly greater percentage of bone-implant contact when compared with the uncoated implants. Results demonstrated that the new FHA surface improved cell adhesion and proliferation. The coating exhibited a bioactive mechanical and histological behavior at bone-implant interface, suggesting that a useful approach by combined coating processes could optimize implant surfaces for bone deposition and early implant fixation.

Abstract: Hydroxyapatite (HA) coatings were introduced onto Poly L-lactic Acid (PLLA) polymer in a controlled manner by immobilized urease method with a shortened precipitation time. Osteoblastic-like cellular responses to the composite were examined in terms of cell proliferation, differentiation and cell morphology, as well as the expression of bone-associated genes. The cells exhibited higher cellular proliferation at 2 and 4 days on the HA/PLLA composite compared to PLLA scaffold, while no significant difference was observed later at 6 days. The alkaline phosphatase (ALP) activity by cells at 7 days was statistically higher on HA/PLLA scaffold than on PLLA. Moreover, the gene expression of ALP and osteocalcin (OC) was up regulated on HA/PLLA composite by RT-PCR analysis. The preliminary study suggested that the use of the controlled modification of hydroxyapatite coating on PLLA scaffold to produce HA/PLLA composite might enhance cellular activity, indicating the potential use for bone substitute in tissue engineering.

Abstract: Although compositional gradients could be manufactured for the functionally graded coating that was showed to improve bonding strength between the coating and the substrate, the biological efficacy of the graded coatings remained unclear. In this study, a functionally graded nanophase hydroxyapatite/bioglass (n-HA/bioglass) coating was prepared on a titanium (Ti) substrate for evaluating peri-implant osteogenesis in a canine model. The bone apposition and osteointegration of n-HA/bioglass coating were investigated at the interface compared with plasma spraying HA (PS-HA) coating. The results showed that the coating degraded gradually over time but not as fast as PS-HA coating did, and that more active bone apposition appeared on the n-HA/bioglass coating. The in vivo study indicated that an early osteogenesis and osteointegration at the interface could be stimulated by the use of n-HA/bioglass coating in biological environment.

Abstract: A novel biomimetic composite consisted of nano β-tricalcium phosphate and collagen (n-TCP/Col.), having similar structure with the natural bone, was produced by a wet-chemical method. The biological effect with and without n-TCP/Col on bone repair and regeneration was evaluated by histological and radiological examination in a rabbit femoral condyle model. The results showed that radiopacity of implant decreased gradually and began to increase at 12 weeks, while no obvious changes for the control. Histological results revealed that trabecular bone formed around the implant at 4 weeks and increased at 8 weeks; By 12 weeks, bone filling with Harvard’s system was observed around the implant. By contrast, only loose connective tissue was seen in control group. This was further illuminated by fluorescence microscopy. The results of this study suggested that the novel nano β-tricalcium phosphate and collagen composite possessed good properties of osteoconductivity and degradation in the biological environment, which could have potential application as a promising bone substitute.

Abstract: Biomimetic nanoapatite coatings was developed by functionally modified methods with a combination of topographic, chemical and biomimetic treatments on the surface of titanium (Ti) substrate. The biological behavior and bioactivity of functionally modified SLA implants with chemical and biomimetic treatments (SCB-treated Ti) using body like solution were investigated to compare with untreated Ti and SLA Ti plates as controls. The cell attachment, proliferation, alkaline phosphotatse (AKP) activity, cell morphology and differentiation were evaluated by using MTT, RT-PCR, scanning electron microscopy (SEM) and confocal laser-scanning microscope (CLSM) analysis system. The results showed that the cell adhesion and proliferation was enhanced on functionalized titanium surface with nano-scale apatite compared to the controls. SEM micrographs also revealed that the osteoblast-like cells spreadly grew along the surface. Cell morphology and differentiation could be further observed distinctly by CLSM graphs. Moreover, mRNA expression of alkaline phosphotatse in nucleus on the SCB-treated Ti increased obviously on the third day compared with the controls. The in vitro results demonstrated the remarkable improvement on cell adhesion and proliferation of the biomimetic nanoapatite on SCB-treated Ti, which could be used for orthopaedic/dental implants.

Abstract: To evaluate the effectiveness of the cell-material in situ on joint resurfacing, a woven fabric polyglycolic acid (PGA) treated with fresh chondrocytes was used for repairing cartilage defects. Full-thickness defects were created in the weight-bearing surfaces of the femoral intercondylar fossa in a rabbit model. The defect was filled with and without PGA under surgical condition. Before implantation, chondrocytes were co-cultured with PGA for one day. The animals were sacrificed at eight weeks after implantation and evaluated grossly and histological score. Morphological examination showed that for PGA/chondrocytes group, the repaired tissue appeared similar in color and texture to the surrounding articular surface. While for the untreated control, no cartilage-like tissue was observed at all defects, but connective fibrous tissue. Histological analysis revealed neochondrogenesis and clusters of cartilage matrix with specific safranin-O staining for the PGA/cell group. The Gross and histological evaluation indicated a significantly higher score for PGA/cell group than for PGA and control group. These results suggest that the woven fabric PGA may facilitate the formation of cartilage tissues by providing a biodegradable and good-handle vehicle for the delivery to and retention of organized cell matrix constructs in vivo site. It might therefore enhance neochondrogenesis because of the superior biodegradable and biocompatible of PGA scaffold sheet, while the more suitable biological environment might sustain cell growth and in situ cell function, suggesting a promising candidate for functional tissue engineering of clinical environment.

Abstract: Bone grafts have been used to fill bone defects caused by disease or trauma. The amount of autografts is limited and allogenic bone grafts may transmit diseases and cause immune responses. Numerous materials have been proposed and used as scaffolds for bone tissue reconstruction. In this study, we tested nanophase PLGA/HA composite with mesenchymal stem cells in vitro to examine its biological response and cellular activity. The nanophase composite was compared to conventional polystyrene on cytocompatibility by cell attachment, proliferation, alkaline phosphotase activity test and scanning electron microscopy (SEM) analysis. The results demonstrated that human mesenchymal cells showed more cell attachment and higher cell proliferation rate when growing on nanophase PLGA/HA composite than those growing on polystyrene alone. And the composite also promoted MSC cells differentiate to osteoblast cells as compared with control. It was suggested that the combination of bone marrow mesenchymal cells with artificial materials or differentiation factors may enhance bone formation and regeneration, nanophase PLGA/HA composite might therefore be a promising scaffold material for bone tissue substitute in clinical application.

Abstract: A novel porous beta-tricalcium phosphate /collagen fibers (β-TCP/CF) composite, having a well-dispersed nano-sized β-TCP in collagen matrix, was developed by a wet-chemical method. The nano-composite was compared to conventional β-TCP on cytocompatibility by cell attachment, proliferation, alkaline phosphotatse (AKP) activity and scanning electron microscopy (SEM) analysis. These in vitro assays showed that the β-TCP/CF composite elicited cell adhesion and proliferation better then controls. Moreover experiments on osteoblast-like cells showed improved cell growth with the highly characterized nanophase structure. SEM micrographs also showed that the nano-sized composite exhibited much more viable cells in attachment on the surface compared with the controls. At 1, 3 and 5 days, AKP activity was not significant different for the tested and control samples, while at 7 day after culture, significantly increased AKP activity was observed for β-TCP/CF than for the control. The in vitro results obtained confirmed the remarkable improvement of cell adhesion and proliferation of the nano-sized β-TCP/CF composite, which may be a new promising candidate for tissue engineered bone substitute.

Abstract: A novel composite of biodegradable Poly-L-lactic acid (PLLA) with the deposition of the nanosized amorphous calcium phosphate (NCP) particles was developed as tissue engineering scaffold. To improve the minor intrinsic healing capacity of cartilage tissue, the porous composite with desired degradation rate was incorporated with basic fibroblast growth factor (bFGF) and evaluated in the in vivo environment. Full-thickness defects were created in the weight-bearing surface of the femoral condyles in a rabbit model. The defect was filled with and without NCP/PLLA scaffold as a carrier of bFGF. Gross morphology for the test implant showed that the defect was filled with regenerated tissue. It resembled cartilaginous tissue and restored the contour of the condyle at 8 weeks after operation. For the untreated control, no cartilage-like tissue was observed at all defects. Histological analysis revealed neochondrogenesis and clusters of cartilaginous extracellular matrix observed with safranin-O staining at 4 weeks for the NCP/PLLA with bFGF treated defects. At 8 weeks after operation, well-formed and mature cartilage was resurfaced the defects. While only fibrous tissue replacement was observed for the control either at 4 or 8 weeks. Special staining for cartilage indicated the presence of highly sulfated glycosaminoglycans and collagen, which were the major extracellular matrices of cartilage. This investigation showed the potential of NCP/PLLA loaded with bFGF in the study of in situ-transplantable carrier to improve healing of cartilage tissue lesion.