Synthesis Of Robust Multifunctional Magnetic Hydrogels And Their Application In Repairing Rheumatoid Arthritis-Induced Cartilage Defects

The magnetic hydrogel prepared by compounding magnetic nanoparticles with hydrogel matrix can achieve image monitoring,controllable drug-release,multi-mode combined therapy after implantation in vivo.Especially in tissue regeneration medicine,hydrogels are very suitable for repairing soft tissue because of their large amount of water,good biocompatibility and highly similar structure to extracellular matrix.However,the currently reported hydrogels are mainly aimed at the repair of non-load-bearing soft tissues,but relatively few reports of load-bearing soft tissue repairs,especially the repair of cartilage defects caused by chronic rheumatoid arthritis?RA?.Therefore,in this paper,a robust multifunctional magnetic double network hydrogel was developed,and the system was further optimized based on the demand for repairing RA-induced cartilage defects.Finally,its ability to inhibit inflammation and repair cartilage were evaluated in vitro and in vivo.The main results are as follows:1.A bondable magnetic nano-Fe₃O₄ composite polyolefin chitosan?AAD-CS-Fe?double network hydrogel system was designed and prepared,then its material properties were characterized.The results show that the multiple ion coordination,hydrogen bond and?-?stacking interaction in the system can significantly improve the mechanical properties?>2MPa?and self-healing of the hydrogel.Meanwhile,changes in composition ratio lead to the controllability of the hydrogel strength,which will further expand the application of this system of hydrogels in biomedical fields.Moreover,the addition of HCl-etched Fe₃O₄ to the hydrogel can endow it with excellent magnetocaloric effect and MR imaging.Finally,to demonstrate the potential of the magnetic AAD-CS-Fe hydrogel implantation in vivo,several3d printing anatomical structures were constructed by printing the hydrogel pre-solution in the saturated sodium chloride receiving solution containing ammonium persulfate.2.Based on the demand for repairing RA-induced articular cartilage defects,the magnetic hydrogel was further optimized,loaded with methotrexate?MTX?and transforming growth factor?TGF-?1?,and its mechanical properties and sustained drug-release ability in vitro were characterized.The results showed that the compression modulus of drug-loaded hydrogel?1.85 MPa?was similar to that of natural cartilage?about 1.5 MPa?,indicating its mechanical properties were compatible with cartilage.In addition,during the two-month monitoring of hydrogels for sustained-release drugs in vitro,both MTX and TGF-?1 were released slowly without explosion,and the heat-induction performance of the hydrogel has no significant effect on drug release,thereby minimizing the toxicity and satisfying the needs of slow release delivery of hydrogels in situ.3.After stimulating macrophages with LPS to mimic the inflammatory damage of joints,it was verified at the cellular level that the drug-loaded hydrogel system can significantly inhibit the release of inflammatory cytokines induced by LPS in a magnetothermal environment.Furthermore,we quantified the specific genes of cartilage-related markers—collagen type II?col II?and aggrecan by quantitative real-time polymerase chain reaction?qRT-PCR?.The results showed that the hydrogel system can promote the chondrogenic differentiation ability of BMSCs cultured on hydrogel,and more importantly,a mild magnetocaloric effect?41??have a tendency to further reinforce chondrogenic differentiation.4.After successfully establishing the model of RA-induced cartilage defects in male rats,hydrogels were implanted into the defects and treated with magnetic-thermotherapy regularly.Finally,the inhibitory effect of hydrogel on inflammation was evaluated by recording the swelling of macroscopic joints and detecting the expression of inflammatory factors in serum.Meanwhile,the ability of hydrogel to promote cartilage repair was evaluated by histological staining.The results show that the robust magnetic hydrogel and its slow-release drugs have a good inhibitory effect on inflammation and promote cartilage repair.Notably,the mild magnetocaloric effect of the implant in situ can further strengthen the treatment of RA and cartilage repair.In addition,the excellent MR imaging of hydrogel can achieve non-invasive monitoring of material degradation in vivo,effectively evaluate the status of in situ cartilage inflammation,and realize the integration of diagnosis and treatment of cartilage defects in vivo.In summary,a novel strategy for preparing robust?>2MPa?and self-healing magnetic double-network hydrogels is proposed.At the same time,this strategy can give the hydrogels excellent magnetocaloric effect,cytocompatibility,adjustable mechanical properties,MR imaging and 3d printability.On this basis,a drug-loaded magnetic hydrogel was constructed by optimizing the hydrogel to meet the needs of repairing the rheumatoid arthritis?RA?-induced cartilage defects.Notably,the hydrogel has the mechanical properties that match the articular cartilage,the ability to deliver drugs slowly in situ for a long time,and the magnetocaloric synergistic effect can significantly inhibit the level of inflammation and promote cartilage repair in vivo and in vitro.Moreover,the hydrogel with good MR imaging can monitor the degradation of material in real time,so it can be used as a good autoradiographic material for repairing diseased articular cartilage.