Magnetic-targeting And Oxygen-generating Nanoparticles For Antimicrobial Photodynamic Therapy Against Periodontal Biofilm

Periodontitis is an inflammatory disease caused by oral biofilms.The inflammation leads to attachment loss,periodontal pocket formation,bone destruction,and ultimately,possible tooth loss.Traditionally,periodontal treatment has involved mechanical debridement to remove the biofilm and calculus that adhered to the infected root surfaces.But mechanical debridement fails to remove periodontal infection in a subset of cases without the ability to approach deep pockets and furcation.Adjunctive local antibiotics are often administered to eradicate or reduce the number of pathogenic bacteria and virulence factor.However,there is increasing attention about the abuse of antibiotics in periodontitis treatment due to the world's public health concern for bacterial resistance.Therefore,new alternative strategies are needed to control biofilm and treat periodontal diseases.Antimicrobial photodynamic therapy?aPDT?is a promising antibacterial therapeutic for periodontitis,that advoid the emergence of drug-resistant strains,with the advantages of easy operation,broad-spectrum antibacterial activity and high efficiency.Although commercial photosensitizer has been widely used in clinic,there are still some problems to be solved urgently.The problems are as follow:?1?the hydrophobic nature of the most photosensitizer molecules leads to the reduced penetration of the photosensitizer into the biofilm matrix;?2?the traditional nanoparticles carrying photosensitizers agents is the low delivery efficiency due to the drainage of gingival crevicular fluid and high saliva fluid turnover;?3?continuous oxygen consumption in intrinsic hypoxic microenvironment would significantly hamper the efficacy of aPDT.In summary,how to improve the effective concentration of photosensitizer in the lesion area and how to make sure the efficacy of aPDT in intrinsic hypoxic microenvironment is of great significance to enhance the periodontitis treatment via aPDT.In the present study,magnetic-targeting and oxygen-generating nanoparticles were designed.The purpose of this study is to investigate the inhibitory effects of the nanoparticles via enhanced antibacterial photodynamic therapy?aPDT?against periodontal biofim.In Chapter two,firstly,magnetic Fe₃O₄,Chlorin e6?Chlorin e6,Ce6?and Coumarin 6?C6?were co-loaded with amphiphilic silane as the carrier to form multifunctional nanoparticles?denoted“Fe₃O₄-silane@Ce6/C6 NPs”?.Then,the physical and chemical properties of nanoparticles were characterized.Antimicrobial photodynamic therapy via Fe₃O₄-silane@Ce6/C6 NPs against periodontal bacteria were tested.Real-time monitor and the magnetic targeted antibacterial effects were also investigated.The results indicated the Fe₃O₄-silane@Ce6/C6 nanoparticles exhibited good water-solubility,chemical stability and biocompatibility.The multifunctional nanoparticles exerted strong anti-biofilm activity against Streptococcus sanguinis,Porphyromonas gingivalis,Fusobacterium nucleatum,with real-time monitoring and magnetically-targeting capacities.In Chapter three,the magnetic-targeting and oxygen-generating nanoparticles?Fe₃O₄-silane@Ce6/C6@MnO₂ NPs?were successfully synthesized by adsorption of MnO₂ on the surface of Fe₃O₄-silane@Ce6/C6 NPs with oxidation-reduction reaction.The physical and chemical properties of nanoparticles were characterized.Real-time monitor and the magnetic targeted antibacterial effects were also investigated.The results indicated the existence of MnO₂ and the strong oxidation susceptibility of the nanoparticles.The results confirmed the loaded MnO₂ did not affect the real-time monitoring function and magnetic targeting function of nanoparticles.In Chapter four,antimicrobial photodynamic therapy via magnetic-targeting and oxygen-generating nanoparticles against periodontal biofilm were tested.The Fe₃O₄-silane@Ce6/C6@MnO₂ NPs exhibited good biocompatibility.The results displayed strong anti-biofilm activity against single species biofilm and the multi-species biofilm of Streptococcus gordonii,Porphyromonas gingivalis,Fusobacterium nucleatum,and showed the suppression of the Fim A-?,Fim A-?,RgpA,RgpB and Kgp DNA expression,that can inhibit bacterial colonization and interfere with the interaction between bacteria and host.In Chapter five,firstly,established a model of periodontal inflammation in rats.Then,magnetic-targeting and oxygen-generating nanoparticles enhanced antimicrobial photodynamic therapy against periodontal inflammation in rats were investigated.The results showed that Fe₃O₄-silane@Ce6/C6@MnO₂ NPs-mediated aPDT could significantly reduce gingival inflammation.In addition,Fe₃O₄-silane@Ce6/C6@MnO₂ NPs-mediated aPDT group significantly reduced the positive cell rate of IL-1?,IL-6,TNF-?.Moreover,the results showed the increased IL-10 and Arg-1 with decreased IL-1b and IL-6.After the administration of Fe₃O₄-silane@Ce6/C6@MnO₂ NPs 60 days,there was no morphological changes or signs of inflammation occurred in the main organs.In conclusion,the present study developed co-loading Ce6 and C6 into the hydrophobic interspace between the octadecyl groups of oleic acid on the surface of Fe₃O₄ and the alkyl chains of silane,then loaded MnO₂ on the surface of Fe₃O₄-silane@Ce6/C6 NPs with oxidation-reduction reaction.The magnetic-targeting and oxygen-generating nanoparticles exerted excellent biocompatibility,real-time monitoring,and magnetically-targeting capacities.Meanwhile,the MnO₂coating modulates the hypoxic microenvironment by in situ generating O₂ through the reaction with endogenous H₂O₂,enhanced the aPDT against the periodontal biofilm to the rats periodontal inflammation treatment.The magnetic-targeting and oxygen-generating nanoparticles have great potential in antibacterial applications to inhibit the occurrence and progression of periodontitis.This novel design provides theoretical basis and experimental support using magnetic-targeting and oxygen-generating nanoparticles to administer aPDT.