Preparation and biological characterization of the mixture of poly(lactic-co-glycolic acid)/chitosan/Ag nanoparticles for periodontal tissue engineering.

OBJECTIVE: This study aims to produce nanoparticles of chitosan (CS), poly(lactic-co-glycolic acid) (PLGA), and silver and investigate the optimal composite ratio of these three materials for periodontal tissue regeneration. METHODS: PLGA nanoparticles (nPLGA), CS nanoparticles (nCS), and silver nanoparticles (nAg) were prepared. The antibacterial properties of single nanoparticles and their effects on the proliferation and mineralization of periodontal membrane cells were investigated. Different ratios of nPLGA and nCS were combined, the proliferation and mineralization of periodontal membrane cells were investigated, and based on the results, the optimal ratio was determined. Finally, nPLGA and nCS in optimal ratio were combined with nAg, and the effects of the complex of these three materials on the proliferation and mineralization of periodontal membrane cells were investigated and tested in animals. RESULTS: The single nanoparticles were found to have no cytotoxicity and were able to promote cell mineralization. nCS and nAg in low concentrations showed antibacterial activity; however, nAg inhibited cell proliferation. The nPLGA and nCS complex in 3:7 ratio contributed to cell mineralization and had no cytotoxicity. nPLGA/nCS/nAg complex, which had the optimal proportion of the three materials, showed no cytotoxicity and contributed to cell mineralization. CONCLUSION: nPLGA/nCS/nAg complex had no cytotoxicity and contributed to cell mineralization. The 3:7 ratio of nPLGA/nCS and 50 µg/mL nAg were found as the optimal proportion of the three materials.

The use of chitosan/PLA nano-fibers by emulsion eletrospinning for periodontal tissue engineering.

OBJECTIVE: In this study, nanofibrous scaffolds base on pure polylactic acid (PLA) and chitosan/PLA blends were fabricated by emulsion eletrospinning. By modulating their mechanical and biological properties, cell-compatible and biodegradable scaffolds were developed for periodontal bone regeneration. METHODS: Pure PLA and different weight ratios of chitosan nano-particle/PLA nano-fibers were fabricated by emulsion eletrospinning. Scanning electron microscope (SEM) was performed to observe the morphology of nano-fibers. Mechanical properties of nano-fibers were tested by single fiber strength tester. Hydrophilic/hydrophobic nature of the nano-fibers was observed by stereomicroscope. In vitro degradation was also tested. Cells were seeded on nano-fibers scaffolds. Changes in cell adhesion, proliferation and osteogenic differentiation were tested by MTT assay and Alizarin Red S staining. Reverse transcription-polymerase chain reaction (RT-PCR) assay was used to evaluate the expression of (Toll-like receptor 4) TLR4, IL-6, IL-8, IL-1ß, OPG, RUNX2 mRNA. RESULTS: It is shown that the mean diameter of nano-fibers is about 200 nm. The mean diameter of chitosan nano-particles is about 50 nm. The combination of chitosan nano-particles enhanced the mechanical properties of pure PLA nano-fibers. By adding a certain amount of chitosan nano-particles, it promoted cell adhesion. It also promoted the osteogenic differentiation of bone marrow stem cells (BMSCs) by elevating the expression of osteogenic marker genes such as BSP, Ocn, collagen I, and OPN and enhanced ECM mineralization. Nonetheless, it caused higher expression of inflammatory mediators and TLR4 of human periodontal ligament cells (hPDLCs). CONCLUSION: The combination of chitosan nano-particles enhanced the mechanical properties of pure PLA nano-fibers and increased its hydrophilicity. Pure PLA nano-fibers scaffold facilitated BMSCs proliferation. Adding an appropriate amount of chitosan nano-particles may promote its properties of cell proliferation and osteogenic differentiation. The higher expression of inflammatory mediators caused by nano-fibers may be regulated via TLR4 pathway.

[Maxillary sinus floor augmentation using gene-enhanced tissue engineered bone].

OBJECTIVE: To evaluate the effect of maxillary sinus elevation with gene-enhanced tissue engineering bone in dogs. METHODS: bone marrow stromal cells (BMSC) derived from dog marrow were cultured, and transduced with the adenovirus carrying bone morphogenetic protein-2 (BMP-2) gene (AdBMP-2), the adenovirus carrying green fluorescent protein (GFP) gene (AdGFP) in vitro. The bone formation ability of gene modified BMSC with scaffold was examined in nude mice and in elevated maxillary sinus of dog. Student's t-test was used for statistical analysis with SPSS 11.0 software package. RESULTS: Gene transfection efficiency reached up to (83.95 ± 2.43)% as demonstrated by GFP expression. Ectopic bone formation was detected in nude mice. As for maxillary sinus floor elevation in a dog model, new bone formation area in the AdBMP-2 gene transduced BMSC with Bio-Oss group was significantly higher than in BMSC with Bio-Oss group at 120 d (P < 0.05). CONCLUSIONS: AdBMP-2 gene transduced BMSC can stimulate ectopic bone formation in nude mice, and promote bone formation and maturation in the dog maxillary sinus.

[Effects of osteogenic growth peptide on bone density adjacent to implant in irradiated tibia of the rabbits].

PURPOSE: To evaluate the effect of radiation and osteogenic growth peptide(OGP) on the bone density adjacent to the implants. METHODS: 24 rabbits underwent 48 implants placed in the tibia, then the rabbits were divided into one control group and two experimental groups randomly. Rabbits in one of the experimental groups were injected with OGP Sol, rabbits in the other groups were injected with normal saline; Then rabbits in the two experimental groups received radiation after the implant wound healed. 12 rabbits were sacrificed at 4 weeks and 16 weeks respectively. The samples were observed with gross, X-ray, histological examination. The data was analysed for Dunnett t test using SPSS13.0 software package. RESULTS: At 4 weeks, the bone density adjacent to the implant of the simple irradiation group was significantly less than that of the control group (P<0.05), while the difference was not significant between the irradiation and OGP group and the control group. At 16 weeks, the difference among the three groups wasn't significant. CONCLUSIONS: Radiation has considerable adverse effect on osteogenesis adjacent to the implants, while systemically administering OGP plays significant roles in the osteogensis of the irradiated rabbit tibia.

[Clinical study of immediate implant-support and mandibular overdentures retained by conical crowns].

PURPOSE: To evaluate the clinical effectiveness and feasibility of immediate implant-supported mandibular overdentures retained by conical crowns. METHODS: In this study, 10 patients with edentulous mandible were included. They were restored by traditional complete denture before operation. All patients received 4 dental implants in the inteforaminal region and had the implants loaded with all overdenture prostheses retained by conical crowns at that day. All patients were followed up for 2, 4, 8, 12, 24, 48 weeks. The stability of implants, the state of peri-implant soft-tissue, marginal bone resorption, the state of osseointegration of implants, and patient satisfaction were evaluated. RESULTS: A total of 40 implants were loaded immediately. All implants had osseointegration. No infections of peri-implant soft-tissue occurred, no implants exhibited peri-implant radio lucencies, marginal bone had no resorption. The patients were satisfied with the outcomes. CONCLUSION: The results of this clinical trial suggest that immediate loading of the implants by conical crowns to support overdenture prostheses for edentulous mandible is predictable, if primary implant stable is.

[Experimental study of maxillary sinus lifting with tissue engineered bone].

OBJECTIVE: To evaluate the effect of tissue engineering bone in maxillary sinus lifting. METHODS: The marrow stromal stem cells of dog were cultured in DMEM containing 100 m1/L fetal bovine serum and induced to differentiate to osteoblasts, which were then inoculated together with Bio-Oss for 5 days. Sixteen dog's bilateral maxillary sinus were elevated. One side was grafted with a compound of BMSC and Bio-Oss and the other side grafted with Bio-Oss alone. The samples were studied by gross, CT, histomorphology and histomorphometrical analysis at the 30th, 90th day after the operation. t-test was used for statistical analysis. RESULTS: In gross view and CT, new bone formation was observed in all maxillary sinus after 30 and 90 days respectively. Histomorphometrical analysis showed much more new callus in BMSC-Bio-Oss group than in Bio-Oss group (P < 0.05). CONCLUSIONS: A better effect of new bone formation could be obtained with tissue engineered bone in maxillary sinus lifting.

[Repair of mandibular central fissures in rabbits with hBMP-2 gene modified tissue engineered bone].

PURPOSE: To evaluate the effectiveness of the tissue engineered bone substitute loaded with periosteal-derived osteoblasts (POBs) transfected by adenovirus mediated human bone morphogenetic protein-2 gene (Ad-hBMP-2) in the repair of rabbit mandibular central fissures. METHODS: 45 rabbits with the soft tissue in the mandibular central fissures removed were randomly divided into 5 groups, group I: Ad-hBMP-2 transfected POBs/bioglass group (n=10); group II: adenovirus mediated enhanced green fluorescent protein (Ad-EGFP) gene transfected POBs/bioglass group (n=10); group III: untransfected POBs/bioglass group (n=10); group IV: single bioglass group (n=10); group V: control group (n=5). The above bone substitutes were implanted in the rabbit mandibular central fissures respectively except group V. The samples were studied by gross, X-ray, histomorphology, histomorphometrical analysis and biomechanics after 2, 4, 8, 12 weeks respectively. One-way ANOVA was used for statistical analysis. RESULTS: In gross view, the rabbit mandibular central fissures in group I were replaced by new bone including cortical bone from the 4th week. X-ray examination showed that the higher bone density was found in the rabbit mandibular central fissures of group I 4 to 8 weeks after implantation. Histomorphometrical analysis showed much more new bony callus in group I than in other groups (P<0.01). The maximal anti-bending load and bending rigidity of the implanted bone substitute of group I were significantly higher than those of group II, III and IV (P<0.01). CONCLUSION: The tissue engineered bone substitute loaded with POBs transfected by human BMP-2 gene could get the best result in the repair of rabbit mandibular central fissures, therefore, it is likely to be used in the repair of alveolar clefts.