Carboxymethyl Chitosan Mediating The Intrafibrillar Mineralization Of Collagen Via Synchronous Self-assembly/mineralization

[Objective]There are a large proportion of elderly patients in clinical.It often can see the patients with dentition defect or even dentition loss in clinical practice.The implant denture,which is more comfortable and more like natural teeth,is accepted by person.However,bone defect is still a big problem for implant surgery.The infection,trauma and other factors can result in bone defect.Thus,artificial bone materials play an important role in the treatment of bone defect.Autologous bone may cause secondary injury to patients.Allogeneic bone may arise difficulties such as immune rejection.The problems inspire more scientists to devote themselves to the research of artificial bone materials.Therefore,biomimetic artificial bone tissue materials with good biocompatibility,excellent biodegradability,outstanding mechanical and biological properties are the focus of research.With the in-depth research on natural bone,the outstanding properties of natural bone are attribute to its precise and orderly hierarchical structure.The biomimetic artificial bone tissue materials imitate the structure of natural bone as far as possible in macroscopic and microcosmic.Over the past decades,researchers often used recombinant non-collagen(NCP)or anionic polyelectrolytes as nucleating inhibitors to prevent premature formation of hydroxyapatite(HAP)in supersaturated calcium phosphate solutions.They could promote the amorphous calcium phosphate(ACP)infiltrate into collagen to form mineralized collagen.In this study,it explored that the process of carboxymethyl chitosan(CMC)stabilizing ACP under acidic conditions and meditated ACP to integrate with collagen during self-assembly.[Method]In the study,the type I collagen gel in acidic condition was prepared.The calcium phosphate particles were stabilized by CMC in acidic condition.After that,the collagen gel and ACP were mixed on dialysis bag and dialysis in buffer.With the p H value rising,the mineralization and self-assembly of collagen also carried on simultaneously.The mineralized collagen was obtained with copper mesh and characterized by transmission electron microscopy(TEM).And then,the mineralized collagen was freeze-dried and characterized.[Result]In this study,the model of synchronous self-assembly/mineralization of collagen(SSM)was established.The results of zeta potential and absorbance showed that the isoelectric point(IP)of CMC was about 3.5.CMC can stabilize calcium and phosphorus under acidic conditions and form nanocomplex of CMC/ACP.During the process of collagen molecule self-assembly,the collagen molecule could bind ACP and then transform to HAP.The formation of HAP was confirmed by X-ray diffraction(XRD)and attenuated total reflection flourier transformed infrared spectroscopy(ATR-FTIR).Scanning electron microscopy(SEM)was used to observe the morphology of mineralized collagen scaffold after freeze-drying.The elastic modulus of collagen scaffold was observed by atomic force microscope(AFM).[Conclusion]CMC is ampholyte electrolyte.The isoelectric point of CMC used in this experiment is about 3.5.In acidic conditions,CMC also can stabilize ACP.In our study,the new model of SSM was stablished.By controlling the p H value of the system,the self-assembly and mineralization of collagen can be carried on in the meantime.It was found that the elastic modulus of the mineralized collagen scaffolds was significantly higher than that of the unmineralized or partially mineralized collagen scaffolds.Therefore,the SSM model provides a new biomimetic mineralization strategy for the tissue engineering.