Mechanical And Degradation Properties Of Bionic Cartilage Scaffolds

Osteoarthritis,sports trauma,and other diseases that cause articular cartilage defects are common in clinical practice,but the avascular nature of articular cartilage makes its own repair ability limited.With the development of tissue engineering technology,the use of tissue-engineered scaffolds to repair cartilage defects has become one of the ideal repair methods.However,at present,tissue-engineered scaffolds cannot meet the clinical requirements.Therefore,it is important to study and prepare a tissue-engineered scaffold with good overall performance for cartilage repair.Considering that the scaffold needs to withstand mechanical load and enhance the lubrication of the joint interface after implantation,this paper adds embedded silica nanoparticles（SiO₂）to the original scaffold（type II collagen（COII）/silk proteins（SF））of the group,and freeze-drying technology was used to Bionic cartilage scaffolds with different ratios（COII/SF and COII/SF/SiO₂,including SiO₂-1,SiO₂-1.5,and SiO₂-2 in COII/SF/SiO₂）were designed.The physical properties（porosity,density,water content,etc.）of the scaffolds were tested,the microscopic morphology of each scaffold was observed by scanning electron microscopy,and the structure of the scaffolds was characterized by infrared spectroscopy.The migration ability of cells in the presence or absence of SiO₂ and the morphology of cells inoculated on different scaffolds were compared,cell migration experiments were performed using the immersion solution of COII/SF and SiO₂-1 scaffolds,and the morphology of cells inoculated on the scaffolds was observed using scanning electron microscopy.The results showed that the SiO₂-1immersion solution did not inhibit cell migration,the COII/SF immersion solution was able to promote cell migration,and the number of cell adhesion on the surface of the SiO₂-1 scaffold was greater.To investigate the effect of the presence or absence of SiO₂ on the macroscopic mechanical properties of the stents,COII/SF and SiO₂-1 stents were selected for rate correlation and cyclic strain experiments,and the results showed that the mechanical properties of SiO₂-1 stents were superior to those of COII/SF stents.In order to investigate the effect of the presence or absence of SiO₂ on the microscopic mechanical properties of the stents,nanoindentation tests were performed on the creep properties of COII/SF and SiO₂-1 stents,and the results showed that the SiO₂-1 stents had stronger creep resistance.In the friction and wear experiments,we focused on comparing the effect of the presence or absence of SiO₂ on the friction performance of the bracket,and investigated the effects of stress and rotational speed on the wear amount and friction coefficient of COII/SF and SiO₂-1 brackets.The results show that the friction coefficient and wear amount of SiO₂-1 bracket are smaller compared with COII/SF bracket under the same conditions.The finite element model was established in ABAQUS,and the subroutine UMESHMOTION was developed secondly with the Archard wear theory to realize the wear simulation analysis of the bionic cartilage stent,and finally the simulation results were compared with the experimental results to verify the reliability of the simulation model.The COII/SF,SiO₂-1,SiO₂-1.5,and SiO₂-2 scaffolds were placed in PBS solution of type II collagenase for in vitro degradation experiments.After 2,4 and 8 weeks of degradation in the perfusion degradation device,the stents were observed using electron balance,scanning electron microscopy and infrared diffraction,respectively.The results showed that under the degradation of type II collagenase,the unstable irregularly curled structures were easily hydrolyzed and converted into stable-folded structures,so the content of irregularly curled structures in the scaffolds decreased and the content of-folded structures increased with the increase of degradation time;the moderate degradation rate was observed for SiO₂-1,SiO₂-1.5 scaffolds.In conclusion,among COII/SF,SiO₂-1,SiO₂-1.5,and SiO₂-2 scaffolds,SiO₂-1scaffold has the best overall performance,and this bionic cartilage scaffold has potential application for cartilage defect repair.