Synthesis And Antibacterial Activity Of Quaternary Ammonium Silane-coupled Core-shell Hollow Mesoporous Silica Nanoparticles Loading With Metronidazole

Objectives:Infections remain the most common clinical complications.However,the traditional antimicrobial treatment,whether systemic or local antibiotic therapies have shown lots of drawbacks.Therefore,localized drug delivery system with powerful and sustained antimicrobial effect is highly desirable.Hollow mesoporous silica nanoparticles(HMS)due to its unique physical and chemical properties,making it promising application in drug delivery.And unlike the common antibiotics,quaternary ammonium silane showed a broader antibacterial spectrum,not easy to cause resistance characteristics.Furthermore,due to the lipophilic-C18H37 alkyl long chain,QAC in dimethyltetradecyl [3-(trimeth-oxysilyl)propyl] ammonium chloride(Si QAC)can covalently grafted onto the HMS surface to obtain quaternary ammonium silane-coupled hollow mesoporous silica nanoparticle(QHMS).QHMS was used to create an antibiotic delivery system.Metronidazole(MDZ),which has specific antimicrobial activity against Porphyromonas gingivalis(P.g),was loaded into the hollow of QHMS to construct a drug delivery system with the dual characteristics of direct contact kill and antibiotic release(MDZ@QHMS).Materials and methods:Part 1Due to the characteristic of active silanol groups(Si-OH)was formed on the surface of the hollow mesoporous silica suspension.QAC groups in dimethyloctadecyl [3-(trimethoxysilyl)propyl] ammonium chloride was grafted onto the HMS surface to obtain quaternary ammonium modified hollow mesoporous silica nanoparticles with lipophilic-C18H37 alkyl long chain.And Metronidazole(MDZ)loaded hollow mesoporous silica(MDZ@QHMS)was obtained through a solvent evaporating method.A series of characterization methods were employed to confirm the orient mesoporous structure and grafted functional groups,including Transmission electron microscopy(TEM),X-ray powder diffraction(XRD),Fourier transform infrared spectroscopy(FT-IR),X-ray photoelectron spectroscopy(XPS)and Nitrogen adsorption and desorption curve analysis.The sodium fluorescein elution assay and the bromophenol blue assay were used to detect the amount of QAC groups success grafted.Ultraviolet and visible spectrophotometer(Uv-vis)was used for the observation of drug loading and release trends.Part 2Human gingival fibroblasts were used to examine the cytotoxicity of MDZ@ QHMS to determine the appropriate antibacterial concentration.Cell counting kit(CCK-8)will be used to evaluate the effect of cell-viability on cell viability during 1 week of co-culture with the material.Further,Escherichia coli(E.coli,ATCC25922),Streptococcus aureus(S.a,ATCC25977)and Porphyromonas gingivalis(P.g,ATCC33277)were employed to form single plaque biofilms to access the antibacterial effects of effective concentration of MDZ@QHMS.The quantitative evaluation results will be described by colony-forming units count(CFU count)and bacterial viability test XTT reagent.And the biofilms were observed under a confocal laser scanning confocal microscope after staining with LIVE/DEAD?Bac Light? Bacterial Viability Kits.Result:1.Through the self-template method,size,pore size,structure,shape controllable hollow mesoporous silicon particles can be successfully synthesized.And QAC long chain can be successfully covalently anchored on the surface of the mesoporous Si-O-Si synthesis of quaternary ammonium silane modified hollow mesoporous.Using QHMS as a drug carrier,a stable MDZ@QHMS drug delivery system was formed by solvent evaporation of loaded metronidazole.This system shows good drug load ability and sustained release.2.MDZ@QHMS showed good biocompatibility when used below 100 ?g/ml.Above 100 ?g/ml,it shows a slight inhibition on the viability of human gingival fibroblasts.Antibacterial experiments within 7 days was observed.A simple 100 ?g/ml QHMS has showed antibacterial effect against Streptococcus aureus and Escherichia coli,but barely no effect on Porphyromonas gingivalis.25-200 ?g/ml MDZ@QHMS showed antibacterial activity against Streptococcus aureus,Escherichia coli,and Porphyromonas gingivalis biofilms.The antibacterial ability increases with the increase of concentration.Conclusion:The quaternary ammonium modified hollow mesoporous silica loaded with metronidazole(MDZ@QHMS)has a stable mesoporous structure and sustained metronidazole releasing profile.It also shows good biocompatibility and antibacterial ability.