Mussel-inspired NHA/OSA Injectable Hydrogel And Application In Bone Regeneration

ObjectiveIn the clinical treatment of bone defects,the traditional method is to implant bone repair material through open surgery.However,most of the bone defects are irregular,the clinically commonly used strip or granular bone repair material cannot fill the entire defect cavity well,thus cannot form good contact with the bone surrounding the defects,eventually adversely affect the bone tissue regeneration and repair.In recent years,with the principle of biological osteosynthesis(BO)has been widely recognized and the rapid development of minimally invasive techniques in orthopaedics,minimally invasive surgery combined with local injection of bone repair materials has attracted increasing attention for the treatment of bone defects,especially lacunar bone defects.It not only solves the problem of bone defect filling,but also avoids a series of complications caused by open surgery,such as infection,skin necrosis and so on.At present,the most commonly used injectable bone repair materials in clinical are calcium phosphate cement(CPC)and α-calcium sulfate hemihydrate(CSH).Among them,CPC has good biocompatibility and in situ self-setting property and the formed material has the advantages of good osteoconductivity and drug loading,etc.CSH has good plasticity and in situ self-setting properties.When mixed with water,it was converted into calcium sulfate dihydrate(CSD)with high density and strength,which is suitable for the repair of bone defects.However,both of them have some drawbacks in the clinical application,CPC has poor injection performance and easy collapsibility in body fluids,while CSH has rapid degradation and lack of osteoinductive activity.Therefore,it is critical to study novel of injectable bone repair materials.Based on the principle of bionics,it is an ideal solution to construct an injectable bone repair hydrogel with natural polymer hydrogel composite hydroxyapatite.However,in the current research and clinical applications,there is still a lack of excellent injectable bone repair hydrogels.This study aims to study a new type of injectable bone repair hydrogel with excellent performance.MethodsIn this study,oxidized sodium alginate(OSA),gelatin(gelatin),polydopamine(PDA)and hydroxyapatite(HA)were used as the main components to prepare an injectable bone repair hydrogel under mild reaction conditions:Firstly,dopamine(Dopamine,DA)was used to modify the nHA.During the polymerization process,DA formed a PDA layer on the surface of HA to form PDA-modified nHA(PHA),and then introduced PHA into the Schiff base reaction system between oxidized sodium alginate and gelatin.Subsequently,the injectability of hydrogels were studied by screening and optimizing the concentration range of PHA to make it suitable for clinical operations,and the morphology,mechanical,swelling,degradation and sustained release properties of different hydrogels were studied to meet clinical needs.Secondly,bone marrow mesenchymal stem cells(BMSCs)were co-cultured with different components and concentrations of hydrogels to study the adhesion,proliferation and differentiation behavior of BMSCs on hydrogel surfaces to explore the cytotoxicity of OSA-Gel-PHA hydrogels and their ability to promote osteogenic differentiation.The bone repair ability of OSA-Gel-PHA hydrogel was explored by establishing a bone defect in vivo and injecting the hydrogel into the bone defect for 12 weeks.ResultsThrough the above study,we have the following results:1.The results of tube inversion and rheological test showed that within the allowable PHA concentration range,the hydrogel gelation time was suitable for clinical operation within the optimized PHA concentration range.2.The results of morphological observation,compression tests,rheological tests,swelling and degradation properties tests showed that the addition of PHA changed the microstructure of the hydrogels from pore to layer,not only improved the compressive strength,toughness,elastic modulus,storage modulus of the hydrogels,but also reduced the swelling properties and degradation rate of the hydrogels,making it more conducive to clinical operations.3.The results of the BMP-2 release properties study showed that the addition of PHA significantly delayed the release of BMP-2,which not only prevented the toxicityof BMP-2 burst release,but also continued to promote bone defect.4.The results laser confocal,MTT assay and alkaline phosphatase(ALP)assay showed that the addition of PHA not only no toxic,but also promotes the adhesion,proliferation and osteogenic differentiation of BMSCs,and within the range allowed by PHA,the higher the concentration,the better the effect of promoting cell adhesion,proliferation and osteogenic differentiation.5.The results of in vivo animal experiments showed that the addition of PHA confers better bone repair performance to hydrogels,and within the allowable range of PHA,the higher its concentration,the better the bone repair performance and the higher the bone maturity.Conclusion1.The injectable properties and material properties of the OSA-Gel-PHA hydrogel meet the clinical application requirements.After screening,the gelation time of 10 wt%and 15 wt% PHA was suitable for clinical operation.The resulting hydrogels have improved mechanical,swelling,and degradation properties and can sustained release BMP-2 growth factor,which is suitable for clinical use.2.OSA-Gel-PHA hydrogel can significantly promote the adhesion,proliferation and differentiation of BMSCs,as well as the repair and maturation of bone tissue.And within the range allowed by PHA,the higher the concentration,the better the effect of promoting cell adhesion,proliferation,and differentiation,and the better the effect of promoting bone repair and maturation.