Design Fabrication Of Molybdenum Oxide-based Hybrid Nanozymes And Antibacterial Application

A rapid increase in methicillin-resistant Staphylococcus aureus（MRSA）induced infection has been noticed in recent years and the biofilm formed by MRSA further delays wound healing,causing a high mortality rate.Nanozymes have received increasing attention in against MRSA stains and biofilms owing to their intrinsic enzyme-like catalytic activities,better stability,low cost and convenient preparation.However,the single nanozyme-mediated catalytic therapy cannot achieve the desired antibacterial effect.Therefore,synergistic enzyme-based strategies need to be developed to obtain better antibacterial effects.Glucose-functionalized Mo O_3-x nanoparticles(Mo O_3-x NPs)synthesized via a one-step hydrothermal method possess excellent photothermal properties as well as bienzyme-like（peroxidase-like（POD-like）and oxidase-like（OXD-like））activities due to the existence of oxygen vacancy structure.With the synergistic effect of photothermal properties and enzyme-like activities,Mo O_3-x nanozyme exhibit significant broad-spectrum antibacterial properties and good anti-MRSA biofilm ability,and they can effectively eliminate MRSA-induced wound infection and accelerate the wound healing,which makes it an excellent antibacterial material.Metal nanoparticles,such as Au,Ag,Cu,Pt,etc.,are currently receiving extensive attention due to their excellent chemical activity and broad antibacterial properties.However,excessive accumulation of metal nanoparticles can cause cytotoxicity and damage to normal cells.Therefore,combining gold nanoparticles with Mo O_3-x nanozyme can not only reduce the cytotoxicity of metal nanoparticles,but also make full use of the properties of metal nanoparticles and Mo O_3-xnanozyme to achieve better antibacterial effects.In this thesis,we developed a safe and effective superoxide radical(O₂^·-)-mediated self-synthesis strategy to prepare Au/Mo O_3-x plasmonic-semiconductor hybrids.And the synthetized Au/Mo O_3-x hybrid was used for the elimination of MRSA-mediated wound infection.In addition,we also successfully synthesized other superoxide radical-mediated self-synthesis of molybdenum oxide-based hybrids.The specific works are as follows:1.Au/Mo O_3-x hybrid was synthesized via a facile and green cascade reaction strategy,including reducing ammonium molybdate tetrahydrate with glucose to obtain glycosylated Mo O_3-x NPs,followed by the reduction of HAu Cl₄ into Au nanoparticles using the resultant Mo O_3-x NPs as the reducing agent.The synthesis mechanism of Au nanoparticles was systematically investigated,proving that O₂^·-plays a key role in the reduction of HAu Cl₄to Au nanoparticles in the presence of H₂O and O₂.Compared with the photothermal conversion efficiency of Mo O_3-x（～41.11%）,the photothermal conversion efficiency of Au/Mo O_3-x hybrid was improved（～52.40%）.Moreover,the POD-like activity of Au/Mo O_3-x hybrid was higher than that of Mo O_3-x NPs,resulting in increased yield of highly toxic·OH.This study provides a basis for exploring Mo O_3-x-based hybrids using a green O₂^·--mediated self-synthesis approach.2.In combination with the enhanced photothermal and POD-like properties,Au/Mo O_3-x hybrid achieves efficient elimination of MRSA bacteria with eradication ratio of～99.76%.The results of biofilm removal experiments also proved the excellent antibacterial performance of Au/Mo O_3-x hybrid on MRSA biofilms.Additionally,the as-prepared Au/Mo O_3-x hybrid exhibit excellent biosafety,which has been verified via in vitro MTT assay and in vivo blood and organ analysis.This demonstrates that the Au/Mo O_3-xhybrid can be a safe and efficient antibacterial agent against MDR bacteria.3.On the basis of the successful synthesis of superoxide radical-mediated self-synthesis Au/Mo O_3-x hybrids with enhanced peroxidase-like activity and photothermal effect.Mo O_3-x NPs was used as reducing agent to reduce Ag⁺,H₂Pt Cl₆,Cu²⁺,and Zn²⁺,and M/Mo O_3-x hybrids（M=Ag,Pt,Cu）were successfully prepared.And it was found that when the metal cations were the same,the rate of reaction varies with anions,as well as the potential of metal cations is related to whether the reaction can proceed positively or not.