Sodium Butyrate-modified Sulfonated Polyetheretherketone Modulates Macrophage Behavior And Shows Enhanced Antibacterial And Osteogenic Functions During Implant-associated Infections

To date,artificial implant materials have been extensively used in orthopedic fields and achieved substantial success.However,two major postsurgical complications may be generated,insufficient implant osseointegration and implant-associated infections,and,consequently,nonunion or malunion of fracture,loosening of the implant,and implants failure may happen.Significant efforts have been made to generate a faultless implant material to directly guide osteogenesis.However,several studies have demonstrated that bone healing is not accomplished simply by a variety of cells,but by a collaboration of multisystem.Studies have shown that the immune system is closely related to bone repair and healing.Therefore,engineering implant surfaces should focus on not only direct antimicrobial and osteogenic properties but also the immunomodulatory properties,which may be an optional approach for the prophylaxis of implant failures.Polyetheretherketone(PEEK)is a promising alternative material,as its good chemical resistance,elastic modulus,and mechanical behavior are similar to those of human cortical bone.In this work,the porous structure on the PEEK surface was fabricated using a sulfonation technique,and then,sodium butyrate was loaded onto the porous sulfonated PEEK.Scanning electron microscopy(SEM)and energy-dispersive X-ray spectrometry(EDS)were used to determine the surface morphology and element distribution of the sample.the release content of sodium butyrate was tested using a visible ultraviolet spectrophotometer(vis-UV).Spread plate method,SEM and phagocytosis assays of macrophages were used to determine the antibacterial and immunomodulatory effects of the samples.Regarding the immunomodulatory osteogenic effect in vitro,we first examine the subtype of macrophages and its cytokines on samples using flow cytometer,immunofluorescence,ELISA and RT-PCR.Then,we performed alkaline phosphatase(ALP)and alizarin red staining,immunofluorescence and RT-PCR tests using conditioned medium.Finally,the in vivo osteomyelitis model and air pouch model were built to validate the antibacterial,osteogenic and immunomodulatory activities of the samples.According to the results,sodium butyrate was loaded onto the 3D porous PEEK Surface,and sustained drug delivery was achieved.Sodium butyrate containing samples showed superior antibacterial properties.Under bacterial stimulation,phagocytosis activities of macrophages increased depending on the sodium butyrate concentration.When removing the bacteria,sodium butyrate containing samples can induce macrophage polarization to M2 phenotype and enhance anti-inflammation related cytokines secretion and genes expression.The osteogenic differentiation of r BMSCs was enhanced when cultured with the cytokines released from the sodium butyrate containing samples stimulating macrophage.The in vivo results indicated that the SP-B2 group exhibits superior anti-infection capacity and was also able to promote new bone formation around the implant.Furthermore,the samples also exhibit the immunomodulatory capacity in vivo air pouch model.In conclusion,the in vitro and in vivo results make it clear that the antibacterial and osteogenic effect of the samples can be enhanced by modulating immunomodulatory capacity.Therefore,immunomodulatory biomaterials regulated the macrophages response under different stimuli providing a new method for designing a smart implant material that possesses superior antibacterial properties and bone repair at specific stages.