Preparation And Properties Of Gadolinium Rare Earth/Chitin Artificial Periosteum

The ideal artificial periosteum should have appropriate pore structure,mechanical strength and flexibility,biocompatibility,bone inducibility,biodegradability,low immune repulsive and anti-inflammatory properties.Although a single natural polymer material such as chitin has certain advantages,it still has shortcomings such as weak mechanical properties and limited functionality,so it can not be fully and efficiently used in bone repair materials.The simple combination of materials can make up for the deficiency of respective components.In this paper,chitin is used as the matrix of artificial periosteum.By introducing other organic molecules or inorganic micro-nano particles,the process and material combination are optimized to promote the improvement of mechanical properties,bone conduction properties,biological activity and controllable degradation,which lays the foundation for the realization of multifunctional integration of artificial periosteum.Firstly,in this paper,chitin powder as raw material,11 wt%Na OH/4 wt%urea aqueous solution as solution system,using low temperature freeze-thaw method to prepare chitin film.During the preparation process,the effects of chitin content,particle size,ultrasonic time,power,freeze-thaw time and soaking solution on the properties of chitin membrane materials were explored to determine the preparation conditions of the optimal mechanical properties of chitin membrane.Further,the chemical groups and crystal structure changes of the regenerated chitin membrane were detected by infrared and XRD.The volume change rate and water content of the membrane were tested to study the changes of the volume and water content of the membrane in the dry-wet state.The hydrophilicity and thermal stability of the membrane were determined by static water contact Angle and thermogravimetric differential thermal analysis.The pore structure changes of chitin film at different degradation time were observed by SEM.The results show that when the chitin content is 7 wt%,the particle size is 150 mesh,the ultrasonic time and power are 30 minutes and 100 W respectively,the freeze-thaw days are 2 days,and the soaking solution is anhydrous ethanol,the tensile strength is strong,up to about 2.4MPa,and the tensile strain is 80%.The chitin used isα-chitin,and the crystallinity of the chitin film decreases slightly after regeneration.The moisture content of chitin wet-dry film is 79.60%,the volume change rate is about 79.57%,and it has good hydrophilicity and thermal stability.The surface of chitin membrane is relatively dense and the pore size varies from 0.2μm to 1.8μm.With the degradation in PBS solution for 14 days,the surface structure was obviously damaged due to degradation,and the pore size increased to0.3μm-6μm.Secondly,by introducing one of organic matter（gelatin,glycerin,etc.）and inorganic matter（hydroxyapatite,silica,gadolinium pentafluoride barium,gadolinium phosphate）with different concentrations in chitin as matrix,the effects of the double composite material system on the physicochemical properties of chitin artificial periosteum were studied.Through mechanical analysis,it is found that the type and concentration of the composite material have obvious influence on the chitin film.When the composites were gelatin（0.4%）,glycerol（1%）,hydroxyapatite（0.2%）,silica（0.2%）,barium gadolinium pentafluoride（0.2%）and gadolinium phosphate（0.1%）,The tensile strength（tensile strain）of the composite membrane can reach 2.8 MPa（108%）,2.0 MPa（80%）,2.1 MPa（111%）,2.7 MPa（118%）,2.6 MPa（101%）and 3.2 MPa（110%）,respectively.Compared with the control group,the tensile strength of chitin membrane was increased by 60%,8.1%,24%,54%,62.5%and 37.5%,respectively.The degradation of the composite membrane of the binary system was studied in the PBS solution containing lysozyme at 37℃.It was found that the degradation of gelatin/chitin membrane was the fastest with a degradation rate of8%,while the degradation of glycerol/chitin,Si O₂/chitin and Ba Gd F₅/chitin was slower with a degradation rate of 2%.The surface structure of individual composites is different,and the three-dimensional network structure of gelatin/chitin and Si O₂/chitin is more obvious.Finally,according to the previous research work,the influence of the three-compound system on the physicochemical properties of chitin membrane is further explored.The effects of the introduction of the third phase on the mechanical properties of organic-organic and organic-organic composite membranes with good mechanical properties and biological activities of gelatin/chitin and HA/chitin were studied.The results show that Gd PO₄/gelatin/chitin and Gd PO₄/HA/chitin have good mechanical properties,and the mechanical strength（tensile strain）can reach 2.9 MPa（130%）and 3.1MPa（110%）,respectively.The tensile strength increases by 28%and 11%compared with the control group,respectively.After 12 days of degradation in lysozyme PBS solution,the degradation rates of Gd PO4/gelatin/chitin and Gd PO₄/HA/chitin composite membranes were 6%and 2%,respectively,indicating that the three composite membranes containing gelatin promoted their own degradation faster.