Effect Of Tannic Acid On Silk Fibroin Regulated Calcium Phosphate Biomineralization

Calcium phosphate is an important element of the large inorganic substance family in nature.Majority of the spine in organisms have calcium phosphate contributes as main component.There are various significant ways to synthesize inorganic minerals with biological identity to induce specific mineralized based products.We can regulate the reaction process of inorganic ions through the bonding between inorganic materials and bioactive organic substance.The processes affected by biomineralization are mainly crystal nucleation,growth,phase transition,orientation and particle assembly.The synthesis of calcium phosphate with different crystal phases by biomineralization has been widely used and remarkable achievements have been achieved.Tannic acid and silk fibroin have shown excellent biocompatibility,biodegradability,and are easy to obtain.In addition,these materials have unique binding properties with inorganic materials,so this is an excellent choice for inorganic materials to biomineralization.In this master thesis,different concentrations of tannic acid were used to react with1mg/m L silk fibroin to explore the changes in the secondary structure of silk fibroin.Biomineralization method was used to explore the regulation effects of reaction system(0?30 ?M tannic acid and 1 mg/m L silk fibroin)on mineralization result of calcium phosphate for 4 h.In this study,the reaction system of 20 ?M tannic acid and 1 mg/m L silk fibroin was used to regulate the mineralization process of calcium phosphate for0?10 h.The pure calcium phosphate mineralization reaction system was used as control group 1,and the reaction system without tannic acid was used as control group 2.The results of this study are as follows:(1)UV-Vis spectrum analysis of the reaction solution of 0?40 ?M tannic acid and1 mg/m L silk fibroin showed that the absorption peaks appeared at 230 nm and 276 nm,which represented the carbon and oxygen double bond of silk fibroin molecular chain and the absorption of UV light by tryptophan.It indicated that tannic acid could have significant bond and interaction with silk fibroin.Using ultraviolet light at 295 nm as the excitation wavelength,the fluorescence emission peak of the solution decreased with the increase of tannic acid concentration when tannic acid reacted with 1 mg/m L silk fibroin at 0?40 ?M.The fluorescence emission peak at 352 nm indicated that part of the fluorescence of tryptophan residues in silk fibroin was quenched by the newly formed hydrogen bond in solution.(2)We analysed the reaction products of 0?30 ?M tannic acid and 1 mg/m L silk fibroin through infrared absorption(FTIR)spectrum,The results showed that with the increase of tannic acid concentration,the infrared absorption peaks of each tannic acidsilk fibroin reaction system increased at first and then decreased.When concentration of tannic acid increased from 0 ?M to 20 ?M,the ? helical structure of silk fibroin increased and ?-folded structure decreased.When the concentration of tannic acid increased from 20 ?M to 30 ?M,the ? helical structure decreased and the ? folding increased.(3)In the solution of 0,10,20,30 ?M tannic acid and silk fibroin with different concentration gradient,from no tannic acid to 20 ?M tannic acid concentration,the number of hydroxyapatite(HA)in the system increased gradually,and the crystal size in SEM image decreased gradually.After that,with the increase of tannic acid concentration,the intensity of the diffraction peak represented by the HA crystal phase and the intensity of the related infrared absorption peak decreased,because the increase of ? helical structure,? folding and the decrease of intermolecular hydrogen bond in the reaction solution of silk fibroin protein promoted the formation of HA microcrystals.(4)The calcium phosphate samples obtained by the reaction group were mainly composed of HA.The ? folded structure of silk fibroin protein in the reaction solution was less,which was conducive to the formation of HA.With the passage of reaction time,the HA in the reaction system increased gradually.A large number of amino acid residues in tannic acid 0 ?M-silk fibroin 50% group promoted the formation of crystal nucleus in the process of HA mineralization,while the folded structure of silk fibroin ?decreased in tannic acid 20 ?M-silk fibroin 50% group,which prolonged the formation time of HA.