The Preparation And Properties Of Functionalized Sodium Alginate Scaffold

In the world,the lack of sources of bone repair materials has become one of the main problems faced by orthopedic clinics,and.the rapid development of bone tissue engineering technology in recent years is an effective means to solve this problem.Among the three elements of bone tissue engineering,the bone tissue engineering scaffold acting as a cell carrier must fully simulate the composition and structure of natural bone tissue to achieve the desired repair effect.3D printing rapid prototyping technology has become one of the most promising technologies in the field of bone tissue engineering due to its capability to accurately control the shape and internal pore structure of the scaffold and realize the preparation of a personalized scaffold that perfectly matches the bone defect area.Sodium alginate（SA）,a natural biological material extracted from brown algae,has been widely used for the preparation of tissue engineering scaffolds because of its good biocompatibility and biodegradability.However,the 3D printed sodium alginate scaffolds also have some shortcomings such as poor mechanical property and low osteogenesis activity.Furthermore,the lack of antibacterial and anti-inflammatory activities will result in surgical failure due to bacterial infection and concurrent inflammatory response induced by the bone grafting process,thus limiting its practical clinical application.Therefore,this paper mainly improves the mechanical stability,osteogenesis activity and gives it antibacterial and anti-inflammatory properties by functionally modifying the 3D printed sodium alginate scaffold,so as to achieve its clinical application in orthopedics.The research contents and results are as follows:1.A 3D printed multifunctional sodium alginate scaffold(IBU-PLLAms@SA-Sr²⁺)was constructed by combining strontium ion(Sr²⁺)crosslinking with cryogenic 3D printing technology,the morphology,mechanical property,drug release performance,anti-inflammatory properties,in vitro biomineralization capacity,in vitro biocompatibility and osteogenesis performance of the scaffold were studied.The results showed that the prepared scaffold had regular large pores,mesopores and small pores connected to each other,and the drug-loaded modified PLLA microspheres with a size of100～200 nm were homogeneously dispersed in the sodium alginate matrix.The experimental results of mechanical properties showed that the scaffold had good mechanical properties.The results of in vitro drug release and anti-inflammatory studies showed that the prepared scaffold had a sustained release performance for IBU drug and thus hold an excellent anti-inflammatory activity.The in vitro biomineralization experiment results confirmed that the scaffold had a strong ability to induce biomineralization.The in vitro biocompatibility experiments indicated that scaffold was not toxic,MC3T3-E1 cells proliferated well on the scaffold,and the scaffold could promote the osteogenic differentiation and bone mineralization of MC3T3-E1 cells.2.A dual-load drug multifunctional sodium alginate scaffold（IBU-PLLAms@SA/HAp-ALN）was prepared by cryogenic 3D printing combined with in situ mineralization method.The targeted scaffold was obtained via the in-situ biomimeticly mineralized deposition of nano-hydroxyapatite crystals on the surface and interior of the scaffold by successively immersing IBU-PLLAms@SA scaffold obtained by cryogenic 3D printing in Ca（NO₃）₂and K₂HPO₄solutions,and the sodium alendronate（ALN）drug was loaded during the mineralization process.The morphology,mechanical property,drug release performance,anti-inflammatory activity,biocompatibility and osteogenesis performance of the scaffold were explored.The results showed that the hydroxyapatite crystals deposited on the surface and inside of the scaffold.It is found that the mechanical property of the scaffold have been greatly improved after being tested by the universal testing machine,and the cell activity experiment confirmed that the scaffold had a good biocompatibility.The results of ALP staining,ALP activity and alizarin red staining experiments showed that the prepared scaffold had the ability to induce bone differentiation of MC3T3-E1 cells.3.A multifunctional sodium alginate scaffold incorporating drug-loaded microspheres(HAp-PLLAms@SA-Sr²⁺)was constructed by using cryogenic 3D printing technology based on Pickering emulsion.With the mesoporous hydroxyapatite nanoparticles（m-HAp）loaded with minocycline（MH）as the stabilizer,the modified polylactic acid/dichloromethane solution containing ibuprofen as the oil phase,the sodium alginate aqueous solution as the aqueous phase,a stable Pickering emulsion was obtained.Then,the resulting emulsion ink was cryogenic 3D printed and crosslinked by Sr²⁺to obtain a dual-load multifunctional sodium alginate scaffold.The internal morphology of the scaffold was observed by SEM,the mechanical properties of the scaffold were characterized by a universal testing machine,the release of ibuprofen and minocycline and the anti-inflammatory activity of scaffold were also studied.The in vitro biocompatibility were evaluated by cell proliferation and cytotoxicity,the osteogenesis activity were investigated by ALP activity,ALP staining and calcium deposition experiments.The modified polylactate microsphere was clearly observed by SEM.The mechanical properties experiments showed that the scaffold had the mechanical properties of elastic bone.The results of drug release and anti-inflammatory experiment showed that the scaffold had a slow release and anti-inflammatory effect.The antibacterial experiment confirmed that the scaffold had an excellent antibacterial activity.The results of the cell experiments showed that MC3T3-E1 cells had a good proliferation status and excellent osteogenic performance on the scaffold.