[Biomechanical study of "mandible-temporomandibular joint" under different loading angles with forsus].

OBJECTIVE: To identify the best loading angle with Forsus for mandible-temporomandibular joint. METHODS: The changes in stress, displacement and rotation of "mandible-temporomandibular joint" were tested under -30 degrees, -15 degrees, 0 degrees, 15 degrees and 25 degrees of loading angles using a primary three dimensional finite element model. RESULTS: From 0 degrees to 25 degrees, with the increases of loading angles the displacement gradually increased. The maximum displacement occurred at chin, with 1.692 mm, 3.456 mm and 4.630 mm displacement under 0 degrees, 15 degrees and 25 degrees respectively. The maximum displacement occurred at the alveolar ridge under -15 degrees loading, which was 0.069 mm. No special stress concentration region was identified. The displacements from infradentale to pogonion gradually increased under all conditions except for the -15 degrees loading. With the loading angles deviated from the baseline farther, the porrect displacements of chin and the counterclockwise rotation became more obvious. CONCLUSION: The loading angles of Forsus appliance should be controlled between 0 degrees and 25 degrees.

Preparation of Coralline Hydroxyapatite Implant with Recombinant Human Bone Morphogenetic Protein-2-Loaded Chitosan Nanospheres and Its Osteogenic Efficacy.

OBJECTIVE: Spinal fusion is one of the most common surgical interventions for spine reconstruction. Despite the efforts to promote osteogenesis after spinal fusion, osteogenesis after spinal fusion remains a clinical challenge and new methods are still needed. The bone morphogenetic protein-2 (BMP-2) is a widely reported factor that can facilitate the osteogenesis in spinal fusion. In previous research, we found that the delivery of chitosan nanospheres could promote the effects of BMP-2 on osteogenic activity. The coralline hydroxyapatite (CHA) is one of the most frequently used implants in bone fusion. However, up to now no study has focused on the osteogenic efficacy of the CHA composite with recombinant human BMP-2 (rhBMP-2)-loaded chitosan nanospheres. This study aimed to investigate the effects of the CHA implant with rhBMP-2-loaded chitosan nanospheres on osteogenesis in spinal fusion. METHODS: The rhBMP-2-loaded microspheres and CHA composite (rhBMP-2 microspheres/CHA) were prepared and were used for implantation of the rats. All SD rats were divided into four groups: the rhBMP-2 microspheres/CHA composite group (containing 0.5 mg rhBMP-2), the rhBMP-2-loaded CHA (rhBMP-2/CHA) composite group (containing 0.5 mg rhBMP-2), the blank CHA group, and the negative control group. The microsphere morphology was scanned and analyzed using a scanning electron microscope. Micro-computed tomography examination and three-dimensional reconstruction were performed 4 weeks after the surgery. Hematoxylin and eosin staining was conducted for histological analysis. Both alkaline phosphatase (ALP) and calcium content were measured. RESULTS: The rhBMP-2-loaded CHA (rhBMP-2/CHA) composite was successfully prepared. Spherical regularity and a smooth and unwrinkled surface of the spheres were observed in all chitosan (CS)/rhBMP-2 microspheres. No side effects, infections, or abnormal behaviors were found in the animals. After 4 weeks of surgery, obvious new bone formation and bone fusion could be observed around the implant in both the rhBMP-2 microspheres/CHA composite group and the rhBMP-2/CHA composite group. No ectopic osteogenesis was found in the vertebral canal or other muscle tissues. After 4 weeks of implantation, in both the rhBMP-2 microspheres/CHA composite group and the rhBMP-2/CHA composite group, osteoid tissues could be found, and bone cells, bone marrow, and trabecular bone turned into mature sclerotin, obvious bone tissue formation could be also seen. Both ALP activity and calcium content in the rhBMP-2 microspheres/CHA composite group (6.52 ± 0.50 kat/g and 17.54 ± 2.49 µg/mg) were significantly higher than in all other groups. CONCLUSION: The composite with rhBMP-2-loaded CS nanospheres could enhance osteogenic efficacy and increase the ALP activity and calcium content. These results might provide a novel method for osteogenesis in spinal fusion and offer new insight into the role of BMP-2 in osteogenesis.

Self­assembled monolayers of alkanethiolates on surface chemistry groups in osteosarcoma cells.

Cell biomedical behavior is influenced by a number of factors, and the extracellular matrix (ECM) of the cellular microenvironment affects certain cancer cells. In the current study, U­2OS cells were cultured on gold surfaces modified with different terminal chemical groups [methyl (­CH3), amino (­NH2), hydroxyl (­OH) and carboxyl (­COOH)]. The results revealed that different chemical surfaces convey different behaviors. The density of the different functional surfaces was confirmed by atomic force microscopy. Cell morphology, proliferation rate and cell cycle were investigated using scanning electron microscopy, cell counting and flow cytometry. In conclusion, the type of chemical group on a biomaterial is an important property for the growth of osteosarcoma cells; ­NH2 and ­COOH surfaces sustained visible cell adhesion and promoted cell growth.

[Biocompatibility evaluation of chitosan-g-polyvinylpyrrolidone].

OBJECTIVE: To evaluate the biocompatibility of chitosan-g-polyvinylpyrrolidone as a new scaffold material. METHODS: The material was tested and measured for water absorption and contact angle, followed by evaluation of the biocompatibility by implantation into rabbits and in vitro cultured with the corneal epithelial cells. RESULTS: The water absorption rate of the material reached 1 100% with contact angle of 83-86. The results of implantation revealed partial degradation of the material 3 months after implantation, and much collagen and numerous corneal stromal cells appeared on the material without obvious inflammation reactions. In vitro coculture with epithelial cells showed good adhesion of the cells to the material which induced no obvious cytotoxicity. CONCLUSION: The novel chitosan derivative has excellent biocompatibility and can be used as a tissue scaffold material.

Preparation and biocompatibility of tissue-engineered scaffold materials based on collagen.

OBJECTIVE: To prepare a tissue-engineered scaffold material using collagen as the matrices and to study the blood compatibility and tissue biocompatibility of this material. METHODS: Physical, chemical and physical/chemical methods were used for the crosslinking of the collagen. RESULTS: Dynamic blood clotting tests indicated that the blood clotting index (BCI) of the crosslinked collagen materials prepared by different means decreased as their contact with the blood was prolonged, and the collagen material obtained after crosslink through 1-ethyl-3-(3-dimethylaminopropyl) carbodiimide method showed the highest BCI after contact with the blood within certain length of time. Hemolysis ratios of all the crosslinked collagen materials were shown to be much lower than 5%, well conforming to the requirement of biomaterials. Scanning electron microscopy showed that the platelets attached to the surface of the crosslinked collagen materials, having a fairly small number, were not morphologically distorted. CONCLUSION: The collagen materials obtained by the 3 crosslink methods have good blood compatibility. The cells grow well on the surfaces of the materials, indicating their good biocompatibility.

Preparation of polylactic acid/chitin composite material and its safety evaluation by animal experiments.

OBJECTIVE: To prepare a scaffold material with good biocompatibility and biodegradability by compounding polylactic acid (PLA) and chitin. METHODS: After preparation of PLA from lactic acid, the compounding of PLA and chitin was carried out by dissolving these 2 materials in one solution for reaction. The composite material was obtained and molded after the solvent was evaporized, and the safety tests of this resultant material were conducted in guinea pigs and New Zealand rabbits, respectively. RESULTS: In allergic test, the guinea pigs responded to the digestion solution of the composite material in almost the same manner as to normal saline (the latter serving as negative control), and no obvious allergic reaction was observed in the animals except those in positive control group. Pyrogenic test by injecting the digestion solution of the composite material in 6 rabbits found a raise in the body temperature less than 0.2 degrees Celsius, with the total increase (adding up the individual temperature raise) less than 1.0 degrees Celsius, to meet the accepted criteria for the pyrogenic test. In subsequent toxicity test, the rabbits showed no signs of agitation or inanimate behavior after injection. CONCLUSIONS: PLA/chitin composite material conforms to the ISO10993-1, and can be used as a basic scaffold material in tissue engineering.

High cleavage efficiency of a 2A peptide derived from porcine teschovirus-1 in human cell lines, zebrafish and mice.

When expression of more than one gene is required in cells, bicistronic or multicistronic expression vectors have been used. Among various strategies employed to construct bicistronic or multicistronic vectors, an internal ribosomal entry site (IRES) has been widely used. Due to the large size and difference in expression levels between genes before and after IRES, however, a new strategy was required to replace IRES. A self-cleaving 2A peptide could be a good candidate to replace IRES because of its small size and high cleavage efficiency between genes upstream and downstream of the 2A peptide. Despite the advantages of the 2A peptides, its use is not widespread because (i) there are no publicly available cloning vectors harboring a 2A peptide gene and (ii) comprehensive comparison of cleavage efficiency among various 2A peptides reported to date has not been performed in different contexts. Here, we generated four expression plasmids each harboring different 2A peptides derived from the foot-and-mouth disease virus, equine rhinitis A virus, Thosea asigna virus and porcine teschovirus-1, respectively, and evaluated their cleavage efficiency in three commonly used human cell lines, zebrafish embryos and adult mice. Western blotting and confocal microscopic analyses revealed that among the four 2As, the one derived from porcine teschovirus-1 (P2A) has the highest cleavage efficiency in all the contexts examined. We anticipate that the 2A-harboring cloning vectors we generated and the highest efficiency of the P2A peptide we demonstrated would help biomedical researchers easily adopt the 2A technology when bicistronic or multicistronic expression is required.

[Three-dimensional finite element analysis of stress distribution in mandible advanced with Forsus].

OBJECTIVE: To construct a three-dimensional finite element model of mandible and to analyze the stress distribution in mandible advanced with Forsus. METHODS: One growing patient with mandibular retrusion was selected. After leveling and aligning with MBT (Mclaughlin Bennett Treriri) straight-wire appliance to achieve the request of forsus with the spiral CT, a three-dimensional finite element model was constructed and the stress distribution in mandible after advancing at 1 second, 15 seconds and 300 seconds was analyzed. RESULTS: The three-dimensional finite element model included MBT straight-wire appliance. The stress concentration areas were located in the front side of the condylar process, the sigmoid notch and mandibular molar areas at 15 seconds and 300 seconds after mandibular advancement. The maximum stress values were 34.47 MPa and 34.45 MPa, respectively. With the extension of loading time, the largest displacement increased from 3.30 x 10(-2) mm to 1.15 mm and the region of the largest displacement extended backwards along the body of mandible. However, the displacement of condyle reduced from 1.65 x 10(-2) mm at 1 second to 3.27 x 10(-5) mm at 300 seconds after mandibular advancement. CONCLUSIONS: The three-dimensional finite element model considered the viscoelasticity and viscoelasticity of mandibular. The result suggested that the stress distribution in the mandible gradually became stable after the application of Forsus and the appliance caused downward and forward mandibular modification.