A Novel Bone-targeting Delivery System Carrying Enoxacin For Eliminating Staphylococcus Aureus Associated Infection With Implantation

Objective:The improvement and innovation of medical implant materials have greatly promoted the development of orthopedic diagnosis and treatment technology,but implant infection after orthopedic surgery is an urgent problem in clinical treatment.Owing to the presence of implants and the formation of bacterial biofilms,the efficacy of antibiotics is limited.Furthermore,osteoclasts can become extremely active,accompanied by bone loss in the infected microenvironment.Therefore,implants often need to be removed.Enoxacin exerts combined antibacterial and osteoclast inhibitory effects.It also plays a role in limiting infections and preventing bone loss.Aspartic acid octapeptide(ASP8)can also recognize and combine with hydroxyapatite crystals in bones and can be targeted to increase antibiotic concentrations in bones.Enoxacin and ASP8 were loaded on mesoporous silica nanoparticles(MSNs)to increase antibiotic concentrations,prevent bacterial biofilm formation,inhibit aberrant osteoclast activities,and reduce bone loss.The main objectives of this study are:(1)to prepare a new bone-targeted antibiotic delivery system to provide a new treatment for implant infections.(2)To clarify the antibacterial effect of enoxacin bone targeted delivery system in vivo and in vitro and the effect of preventing and treating bone loss in vivo.Method:1.Enoxacin and ASP8 were loaded on mesoporous silica nanoparticles(MSN)to prepare enoxacin bone-targeted drug delivery system(Gen@MSN-D).Record and analyze the characterization data of Gen@MSN-D by transmission electron microscope(TEM),dynamic light scattering(DLS),Fourier transform infrared spectroscopy(FTIR),thermogravimetric analysis(TGA),and in vitro drug release experiments.2.The antibacterial effect of Gen@MSN-D in vitro was confirmed by the antibacterial performance experiments such as the minimum inhibitory concentration(MIC),plate colony count,crystal violet staining,scanning electron microscope(SEM)and fluorescent inverted microscope.3.Construct a 12-week-old SD rat in vivo fluorescence model,inject the same dose of fluorescent MSN and fluorescent Gen@MSN-D into the tail vein,euthanize the animals 4 hours and 72 hours later,and take the main organs(heart,liver,spleen,Lung,kidney,femur),fluorescence signals from various organs of each group of rats were detected using an in vivo fluorescence imaging system.To clarify the in vivo bone targeting of Gen@MSN-D.4.A 12-week-old SD rat femoral bone was implanted with a titanium rod and injected with Staphylococcus aureus to construct an implant infection animal model.The same doses of Gen@MSN-D,MSN,EN(enoxacin)and NS(normal saline)were injected intraperitoneally for 4 weeks.Microbiological analysis of the surface of titanium rods,micro-CT scans of bone tissue,and HE and TRAP staining of bone tissues were used to determine whether Gen@MSN-D has anti-infective and bone loss prevention effects in vivo.Result:1.Through the analysis of the characterization data of Gen@MSN-D,it was proved that inosinacin and ASP8 bone targeting groups were successfully loaded on MSN,and Gen@MSN-D has a good drug loading rate and sustained release effect.2.A series of in vitro antibacterial performance experiments proved that Gen @MSN-D has antibacterial effect in vitro.3.The in vivo fluorescence imaging test table proves that Gen@MSN-D has bone targeting in vivo.4.Microbiological analysis of the surface of the titanium rod,micro-CT scan of the femur,and HE staining of the bone tissue show that Gen@MSN-D not only has antibacterial effect in the body,but also can inhibit the activity of osteoclasts to reduce bone loss.Conclusion:Gen@MSN-D is a new type of drug delivery system with safety,targeting and sustained release properties.It not only has excellent antibacterial properties,but also can prevent bone loss.It provides a new method for the prevention and treatment ofpostoperative infection of orthopedic implants.