| BackgroundIn recent years, with the development of economics, persons’demands for quality of life have become increasingly high. Implant denture gradually become the first choice for the treatment of prosthodontics because of its good resumption of masticatory efficiency, high degree of comfort and other advantages. However, alveolar bone loss due to periodontal disease, missing teeth for a long time, and some other factors, has been limiting the expanding of implant denture. Many scholars have been exploring various ways to solve the problem of inadequate bone mass at the edentulous ridge. Guided bone regeneration (GBR) is a new technology for deflecting the growth of soft tissues away from defect area by a barrier membrane to promote the growth of new bone, which is an effective method to increase bone mass in the site needs implant denture. Scientific name of chitosan(CS) is poly glucosamine, which is a polysaccharide of straight chain from chitin with de-acetyl. CS is easy to become film, biocompatible and biodegradable, and has become the focus of research for matrix material of GBR membrane. Hydroxyapatite (HA) is the main component of bone and teeth of human being and other vertebrates, which can induce the growth of bone tissue around the inplants. As a result, HA is proved as suitable substitute materials for bone tissues. Bone m(?)phogenetic protein (BMP) is a multifunctional growth factor in the bone matrix, which belongs to the transforming growth factor (TGF-β) superfamily. BMP is a functional protein with highly conserved structure, and gets its name because it can induce undifferentiated mesenchymal cells differentiate into chondrocytes and osteoblasts, and has the biological characteristics of promoting bone formation. BMP-2owns the most powerful activity for inducing bone tissues regeneration among BMP members. Many experiments show that recombinant human bone morphogenetic protein (rhBMP-2) can promote the repair and remolding of bone tissues.ObjectiveThe main purpose of this study was to solve the problem of inadequate bone mass in implantology because of frontal resorption caused by periodontal disease, tooth loss for a long time, and some other reasons. In this study, chitosan/hydroxyapatite/rhBMP-2(CS/HA/rhBMP-2) composite membranes were prepared with a new method of generation in situ, and its biosafety was detected.Materials and MethodFirst of all, quantitative calcium and phosphate ions were mixed, and chitosan was dissolved in the resultant solution by adding acetic acid. Put this liquid in prepared grass moulds to form uniform membranes. Then, the solid dry chitosan membrane, containing calcium salt and phosphate, was harvested by lyophilization. CS/HA membrane was prepared by putting the membrane into an alkaline solution. After that, the membrane was taken out of the alkaline solution and rinsed thoroughly by deionized water until neutral PH, and then was dried by lyophilization again. The solution containing1.0μg of rhBMP-2was dropped to each membrane with diameter of10mm. The CS/HA/rhBMP-2composite membrane was finally dried at room temperature. According to the pharmaceutical industry standards of the People’s Republic of China, biosafety of this CS/HA/rhBMP-2composite membrane is examined by rat oral acute toxicity test, sensitization test at guinea pigs’skin, and cell toxicity test at hela cells.ResultThe CS/HA/rhBMP-2composite membrane is prepared successfully. Its leaching liquor is detected in rat oral acute toxicity test, and the result is negative because all rats fed by the leaching liquor have no low rate of weight increase or any toxic phenotype. In the sensitization test at guinea pigs’ skin, all individuals attached by CS/HA/rhBMP-2composite membrane have no allergies in direct contact test or provocation test. In the molecular filtration test of cell toxicity test, the cellulose acetate membrane staining intensity was no significant change after incubated with the CS/HA/rhBMP-2composite membrane for2h test, which means non-cytotoxic. The bottom of the test samples were incubated for24h test, and cellulose acetate membrane staining intensity was reduced, but did not appear unstained area, which means only mild cytotoxic. In the cytotoxicity test of the agar overlay method, the fading index and solubility index are both0, and the cell response is graded as0. This result proves the composite membranes have no cytotoxicity.ConclusionIn situ prepared CS/HA/rhBMP-2composite membranes tested by rat oral acute toxicity test, the guinea pig skin sensitization, cytotoxicity test was proved as no acute toxicity, low allergenic and low cytotoxicity. The CS/HA/rhBMP-2composite membrane is safe and owns the potential as a new kind of GBR membrane. |
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