| Objective: Methacrylated Gelatin(Gel MA)hydrogels have stimulated considerable interests in the field of tissue engineering.However,the mechanical properties and the pore size of most hydrogels are undesirable especially for their applications in bone tissue engineering.Up to date,a number of works have been carried out on the impact of the concentration of Gel MA,photo-initiator,methacrylic anhydride(MA),as well as the ultraviolet dose,and the additives,on the properties of GelMA hydrogel.However,little attention has been paid to the effect of the freezing temperature and freezing time of GelMA prepolymer solution on the structures and properties of Gel MA.Accordingly,in the first section of this dissertation,the pore size and properties of GelMA prepolymer solutions treated with different freezing times and freezing temperatures were studied under the same exposure to ultraviolet(UV)light.In addition,C2C12 cells were adopted to investigate the biocompatibility of GelMA by evaluating the adhesion and spread of cells.In the experiments,we found that the GelMA hydrogel was desirable scaffold for bone tissue engineering except for its poor mechanical properties.Therefore,in the second section of this dissertation,meta-analysis was adopted to study the effects of different additives on the mechanical properties of GelMA hydrogels in order to improve the mechanical properties.Methods: In the first section of this dissertation,GelMA prepolymer solution was synthesized by the well-documented standard methods.This solution was respectively placed at-20 ?,-80 ? and-196 ?(liquid nitrogen),and some samples were froze for 2 days,and the others were froze for 22 days,followed by lyophilizing.Photoinitiator was added into the lyophilized GelMA prepolymer with different freezing temperatures and freezing times and the mixture was dissolved in PBS,exposed to ultraviolet(UV)light.The influences of different freezing temperatures and times on the pore size were evaluated.And the effect of distinct pore size on swelling properties and mechanical properties was also investigated.Moreover,mouse muscle myoblasts(C2C12)were seeded on the surface of the GelMA hydrogels,and the adhesion and spread of C2C12 cells were studied.In the second section,literature was searched in the common academic database,then the relative literature was screened,and the data for meta-analysis was extracted.Finally,the meta-analysis was performed using Review Manager.Results: In the first section,it shows that the freezing temperature had a significant effect on the pore size of GelMA hydrogels when the freezing time was short(2 days),while it had no obvious effect when the freezing time was long(22 days).Moreover,when the freezing temperature was fixed,the freezing time would affect the pore size of GelMA hydrogels.We have also found that the swelling properties and mechanical properties of GelMA hydrogels were independent of the freezing temperature and time.In vitro cell culture showed that the C2C12 cells were tightly attached to the surface of GelMA hydrogels,and the GelMA hydrogels placed at-80 ? for 2 days proved to be optimal for the adhesion and spread of cells.The meta-analysis in the second part showed that there was significant heterogeneity among the included studies.However,the difference between the experimental group and the control group is statistically significant,and the additives can increase the mechanical properties of GelMA hydrogels.The results of subgroup analysis between the control group ? 5% GelMA hydrogel,5% ~ 10% GelMA hydrogel and ? 10% GelMA hydrogel showed statistical differences between the subgroups,and the concentration of GelMA hydrogel is one of the sources of heterogeneity.Conclusions: 1.Freezing temperature and freezing time can affect the pore size of GelMA hydrogel;2.Addition of additives can improve the mechanical properties of GelMA hydrogels,and the concentration of GelMA hydrogel is one of the sources of heterogeneity. |
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