| Bone tissue engineering has been a hot topic of research in regenerative medicine for the past two decades.Bone materials used to treat skeletal defects,delayed recovery or non-recovery may be both autologous and allogeneic materials.Autologous materials require separate surgery to remove from elsewhere in the patient’s body and are prone to complications related to pain in the donor area,hematoma in the donor area,etc.Common allogeneic materials include metals,ceramics,and polymers.Metallic materials have sufficient mechanical properties to be used as artificial joints and implant firmware,but the surface interface resistance of metallic materials is too high due to the difference in electronic and ionic conductivity.Ceramics are biocompatible bone repair materials,but poor electrical conductivity and mechanical properties are still the biggest challenges limiting their clinical application.Most polymer materials are widely studied as bone materials because of their advantages,such as good biocompatibility and degradability,but they also have defects such as poor mechanical properties.If there is a material that can perfect the above defects,it can be used as a material scaffold in the human body to provide a climbing bridge for new bone tissue in the interstitial space,and provide a platform for cells and growth factors to play their physiological roles,and ultimately degrade and resorb in vivo and be replaced by new bone tissue.Therefore,the main research goal of this topic is to prepare artificial bone replacement materials with reasonable electrical conductivity,mechanical properties,degradability,and biocompatibility.In this paper,sodium polyacrylate hydrogel scaffolds were prepared by using sodium polyacrylate as raw material combined with 3D printing technology,and then the conditions of hydroxyapatite formation on the surface of hydrogel scaffolds were explored,and a cyclic immersion experimental method was designed by using chemical precipitation method with Ca Cl2 and Na2HPO4 solutions,and experimental control groups with different cycles were prepared.The properties of hydrogel scaffolds such as electrical conductivity,swelling,in vitro degradation and protein adsorption were investigated by thermogravimetric analysis and other tests,and then the formation of hydroxyapatite on the hydrogel surface was investigated by XRD and scanning electron microscopy,and the mechanical properties were tested.Finally,cellular experiments were carried out,and osteoblasts were cultured on sodium polyacrylate hydrogel scaffolds,and cytotoxicity was detected by scanning electron microscopy and MTT,and then the applied electric field was applied to the hydrogel scaffolds,and cytotoxicity under electrical stimulation was detected by AO/EB,and the effect of osteogenic differentiation under electrical stimulation of cells was detected by ALP kit and protease blotting.The electrical conductivity results showed that the sodium polyacrylate hydrogel scaffold could reach a maximum conductivity of 0.16 S/m and a minimum of about 0.011 S/m.The electrical conductivity of the skull was in the range of 0.0042S/m-0.3 S/m,and the resistivity of all four cycles was within its range,indicating that the sodium polyacrylate composite hydrogel scaffold has great potential for transmitting bioelectrical signals via microcurrent in the human body.The results of thermogravimetric analysis showed that the percentage of minerals in the four cycles was 7%,12%,15%and 22%in order,and the percentage of hydroxyapatite as the most important inorganic material in human bone was about 60%,thus,it can be presumed that the hydrogel scaffold prepared in this project needs further increase in terms of inorganic mineral content to become a bone replacement material.The swelling performance analysis showed that the weight of all hydrogel scaffolds did not increase significantly after 7 days of immersion,and there was no statistical difference with the weight of the initial hydrogel,which verified that the sodium polyacrylate hydrogel had the property of non-swelling within one week of implantation,and the in vitro degradation experiment showed that the weight residual ratio of each hydrogel group was higher than 50%within 8 days,indicating that the sodium polyacrylate hydrogel scaffold would be implanted initially in cranial bone repair applications provide temporary support.Protein adsorption experiments showed a substantial increase in protein adsorption in the first 5 hours and a stabilization of protein adsorption in the second 15 hours for four groups of hydrogel scaffolds with different cyclic immersions,and the hydrogels exhibited good protein adsorption ability,and hydrogel scaffolds with good protein adsorption ability facilitated cell adhesion and proliferation,which would allow osteoblasts to form calcified bone tissue in vivo,according to the order of proliferation and differentiation development.Thus,it shows good biocompatibility.The tensile test results show that the fracture strength of sodium polyacrylate hydrogel is 150 k Pa,and it can recover its original shape in multiple tensile cycles,showing good mechanical properties.The above experimental results showed that the sodium polyacrylate hydrogel scaffold has the potential to be used as a replacement material for bone defects in terms of electrical conductivity,swelling,in vitro degradability,biocompatibility,and mechanical properties.MTT,SEM,and AO/EB results showed that sodium polyacrylate hydrogel scaffolds were not toxic to cells,and cells could adhere and proliferate on scaffolds.The results of the osteogenic differentiation assay showed that 100 m V voltage had no obvious effect on promoting osteogenic differentiation of K7M2 WT cells and Saos-2cells.150 m V voltage promoted osteogenic differentiation of Saos-2 cells.200 m V and250 m V had obvious effects on promoting osteogenic differentiation of K7M2 WT cells and Saos-2 cells,of which 250 m V had the most significant effect on promoting osteogenic differentiation.In summary,a hydrogel material with reasonable electrical conductivity,mechanical properties,degradability,and biocompatibility was prepared,and the material can promote osteogenic differentiation of osteoblasts under electrical stimulation. |
