Regulation Of Collagen Mineralization And Dentin Repair By Succinic Acid

Biomineralization is an important process for hard tissue formation in organisms.The biominerals formed by biomineralization have a multi-level ordered structure,excellent mechanical properties,and important physiological functions,which inspire the design of organic-inorganic composite biomaterials and the preparation of biomimetic mineral materials for in vivo and in vitro hard tissues repair.The tooth is a product of biomineralization,but poor oral hygiene can lead to pathological demineralization of teeth,which causes dental caries.Severe dental caries can lead to damage and loss of dentin.Repair dentin by biomimetic mineralization is a future dental restoration technology.Previous studies have found that citric acid,a tricarboxylic acid cycle product that is enriched in hard tissue minerals,can promote collagen mineralization and dentin restoration.By literature research,we found that succinic acid is also an important product in the tricarboxylic acid cycle,which can be enriched in the calcified tumor tissues.We hypothesize that succinic acid may also be an important biomolecule that regulates collagen mineralization.Therefore,the focuses of this paper are on the effect of succinic acid on collagen fiber mineralization and dentin remineralization.The first chapter includes five portions.The first part mainly introduces the background of biomineralization.The second part introduces the hierarchical structure of teeth and the relationship between collagen and minerals.The third part introduces the traditional way of tooth restoration and its drawbacks.The fourth part mainly introduces collagen mineralization which includes the structure of collagen,mechanisms of collagen mineralization,and chemical factors that promote collagen mineralization.The fifth part introduces the biological background of the tricarboxylic acid cycle and the correlation between succinic acid and tumor calcification.The second chapter is the experiments on the collagen mineralization processes.It includes the in situ observation of the collagen mineralization process by atomic force microscopy and laser confocal microscopy.the chemical and interaction analysis of the phase transformation process of collagen mineralization.The results indicate that the binding/chelating of calcium on collagen is important on collagen mineralization,and therefore,we speculated that the organic poly-acid that can coordinate with calcium might play important roles in regulating collagen mineralization.The third chapter is the effect of succinic acid on collagen mineralization.the regulation effects of succinic acid on collagen mineralization are tested by a monolayer collagen fiber model and the collagen gel three-dimensional model.The interaction of succinic acid and collagen is analyzed by FTIR,the binding of calcium ion on collagen is analyzed by ICP,and the p H curve is applied to study the effect of succinic acid on mineralization kinetics.The intra-fiber mineralization structure of mineralized collagen was verified by ultra-high-resolution random optical microscopy.The fourth chapter is the application of succinic acid on dentin remineralization.The dentin slices were obtained by ultra-thin microtomy,the degree of dentin remineralization was observed by transmitting electron microscopy.The mechanical test of the recovery of dentin by dentin remineralization is tested by nanoindentation.The potential cytotoxicity and activity effects of succinic acid are also tested.In this thesis,we found that a high concentration of succinic acid(10 m M)can significantly promote collagen fiber mineralization and dentin remineralization.After dentin is remineralized,its mechanical properties return to the level of natural dentin.Through spectroscopic analysis,element analysis,adsorption curve,and mineralization kinetics,we have revealed the molecular mechanism of succinic acid regulating the mineralization of collagen fibers and dentin: succinic acid is first adsorbed on collagen fibers through molecular hydrogen bonding(adsorption amount > 4 wt%).With the help of succinic acid in collagen fibril,it can enhance the calcium enrichment of collagen fibers,thereby promoting calcification.By the above research,on the one hand,we have provides a chemical understanding of the tumor calcification process by the enrichment of succinic acid in tumor tissues;and on the other hand,the promotion effects of succinic acid on collagen mineralization that revealed by our experiments and its mechanism might also shed lights on the design of dentin remineralization promotors.