The Effect Of Fiber-reinforced And Quenching Method On The Mechanical Properties Of Zein Porous Scaffolds

Bone tissue engineering materials mainly include two categories: artificial synthetic materials and natural materials.Commercial artificial bone materials are mainly inorganic and composite materials,which has complex preparation process and brittle mechanical properties.Natural materials mainly include processed natural bone and natural polymer materials.The source of autogenous bone is limited and it will cause secondary surgery pain.Allograft bone will have the risk of immune rejection.Natural polymer materials,a wide range of sources,low cost,and good biocompatibility,which will help cell adhesion,proliferation,differentiation and so on.And the processability is good and the process is simple.However,the mechanical strength of these materials is not good.Zein,a plant-derived protein,has a wide range of sources and low cost.As a kind of bone tissue engineering materials,zein has a certain mechanical strength,can meet the needs of non-bearing bone.However,mechanical properties of zein need to be strengthened on the bearing bone.The purpose of this study is to improve the mechanical properties of zein by a simple,energy-saving and environment-friendly method,which makes it more widely used in bone tissue engineering.In this study,there are two parts,using fiber-reinforced and quenching way to improve the mechanical properties of zein.First,in the section of fiber-reinforced method,liquid nitrogen grinding was used to disrupt continuous,light-weight zein electrospinning films to obtain small fibers.The diameters of these small fibers were 1.28 0.28 μm and the lengths of fibers were 7.21 3.42 μm.After grinding,the modified fibers had no effect on the morphology.In the process of preparing fiber scaffolds,pore-forming agent(mannitol)could be removed by soaking in room temperature water,and the fiber structure could be controlled to obtain three-dimensional porous fibrous scaffold.Adding the mannitol as pore-forming agent,whether modified or not,the compressive mechanical properties of fiber-reinforced scaffolds could increase 3 to 6 times.By the recrystallization method,we could get the fiber-reinforced scaffolds,whose pore sizes were between 200 μm and 300 μm,and the mechanical properties of fiber-reinforced scaffolds were obviously higher than those without fibers.L929 cells were used to measure the bioactivity by CCK-8 in blank group,unmodified group and modified group.It was found that the presence of fiber did not affect the cell growth.In the section of quenching method,it was found that the quenching treatment significantly improved the compression,bending and tensile properties of the zein porous scaffolds when the porogen content was 39%(w/w).However,when the content of pore-forming agent increased to 60%(w/w)or 70%(w/w),the mechanical strength of the zein porous scaffolds did not improve significantly.Specially,when the content was 70%(w/w),the compression and bending performance of the zein porous scaffolds would decreased.This may be due to the large discontinuities of structure as the result of large porosity.Based on the results of circular dichroism,it was found that the α-helix content of the scaffold decreased and the β-sheet content of the scaffold increased by high temperature treatment and quenching treatment,which may be the internal cause of the increase of the mechanical strength of micro-compression.