Study On The Detection And Inactivation Of Pathogenic Bacteria Based On Responsive Catalytic Nanomaterials

Food safety has become one of the major public health issues in the world,seriously threatening human life and health and social stability.Pathogenic bacteria are the main cause of foodborne diseases,environmental contamination and tissue infections,posing a serious threat to food safety.An infection caused by pathogenic bacteria can endanger human life even at very low levels.Therefore,detection and inactivation of pathogenic bacteria are significant means of reducing the threat of bacterial infections.However,most current investigations focus on the detection of pathogenic bacteria without inactivating them,which may lead to secondary contamination and transmission of pathogenic bacteria after determination.To prevent secondary contamination of bacteria after detection,the construction of a new platform that integrates the detection and inactivation of pathogenic bacteria is the focus of current research efforts.In this work,a chemiluminescent sensing platform was constructed based on the catalytic properties of nanomaterials for the sensitive detection of pathogenic bacteria.Meanwhile,we combined various antimicrobial strategies to inactivate pathogenic bacteria after detection to achieve susceptibility detection and efficient inactivation of bacteria.A MTPE-FCy P aggregation-induced emission（AIE）molecule was used to build a chemiluminescence-based ratiometric sensing platform for sensitive point-of-care testing（POCT）of pathogenic bacteria.The nanopolymers(DSPE-AIE_NPs)prepared by the nanoprecipitation method exhibit oxidase-like properties（refer to as AIEzyme）and can trigger long persistent chemiluminescence of luminol（LUM）with strong intensity in the absence of H₂O₂.The chemiluminescence emission can be monitored with naked eye for over2 h.The AIE/LUM/FL chemiluminescence,which is used to construct a ratiometric biosensor for detection of pathogenic bacteria,is further improved based on the chemiluminescence resonance energy transfer（CRET）mechanism.Adenosine triphosphate（ATP）in bacterial lysates can break down the ZIF-8 nanomaterial encasing fluorescein（FL）,changing the color of the chemiluminescence from blue to green as a result of the CRET between the released fluorescein and LUM.Subsequently,an integrated smartphone and a portable sensor platform were employed to achieve an instant quantitative analysis of Escherichia coli（E.coli）in the range of 10-10⁷ CFU/m L,and the detection limit was 1.75 CFU/m L.Meanwhile,the POCT platform showed good anti-interference ability and potential application in actual sample detection.Nanopolymers（F127@CPPO/BBR/GOD）with multifunctional properties were prepared based on the developed novel CPPO/BBR chemiluminescence system,to construct chemiluminescence-driven photodynamic therapy（PDT）and drug synergy strategies for efficient inactivation of methicillin-resistant Staphylococcus aureus（MRSA）and kanamycin-resistant Escherichia coli（KREC）.Glucose oxidase（GOD）encapsulated in the nanopolymer slowly catalyzes the continuous generation of H₂O₂ from glucose,while the energy generated from the oxidative decomposition of bis（3,5,6-trichloro-2-pentyloxycarbonyl phenyl）oxalate（CPPO）by H₂O₂ is transferred to photosensitive berberine hydrochloride（BBR）,which emits green chemiluminescence while continuously generating singlet oxygen（¹O₂）to achieve efficient inactivation of bacteria.Meanwhile,BBR,as a quaternary alkaloid isolated from the Chinese medicine Huanglian,possesses antibacterial properties.Consequently,the synergistic effect of chemiluminescence-driven PDT and BBR drug therapy efficiently eliminated drug-resistant bacteria,with antibacterial efficiencies of up to 99.82%against MRSA and 99.73%against KREC,respectively.Meanwhile,the nanopolymer could further inhibit the formation of bacterial biofilm.The F127@CPPO/BBR/GOD developed is expected to be used as a wound dressing for the treatment of diabetic wound infections and ulcers.Based on the high catalytic properties and good photothermal conversion ability of the nanocomposite Zr-Fc/Cu O₂,acid-responsive chemodynamic therapy（CDT）and low-temperature photothermal therapy（LT-PTT）was constructed to promote each other as an antibacterial strategy for the efficient inactivation of drug-resistant pathogenic bacteria MRSA and KREC.The acidic microenvironment formed by bacterial metabolism drives the decomposition of Cu O₂ in Zr-Fc/Cu O₂ to produce Cu²⁺and H₂O₂,which generates a large number of cytotoxic hydroxyl radicals（·OH）through the Fenton(Fe²⁺-H₂O₂)and Fenton-like(Cu²⁺-H₂O₂)reactions for effective CDT.Meanwhile,the thermal energy generated by Zr-Fc/Cu O₂ as a photothermal agent under near-infrared（NIR）irradiation is not only effectively transferred to the attached bacteria,but also accelerates the acid decomposition of Cu O₂ on the surface of the material,thus enhancing CDT.Moreover,the excess·OH produced during CDT disrupts the heat shock protein（HSP）system of bacteria,allowing LT-PTT to inactivate pathogenic bacteria without thermally damaging the surrounding stroma and normal tissues.The synergistic effect of CDT and LT-PTT promoted each other to achieve efficient inactivation of drug-resistant bacteria,and the antibacterial efficiency against MRSA and KREC reached 99.96%and 99.81%,respectively.The constructed platform could further inhibit the formation of bacterial biofilm.The Zr-Fc/Cu O₂antibacterial platform constructed is expected to be used as a wound dressing for the treatment of pathogenic bacterial infections in wounds.For sensitive detection of Staphylococcus aureus（S.aureus）and effective killing of the bacteria after detection,an integrated platform of pathogenic POCT and photothermal inactivation based on the CRET mechanism/PTT antibacterial was constructed.Vancomycin（Van）on the surface of Fe₃O₄@Van was used to target Gram-positive bacteria and the boronic acid group in UIO-B（OH）₂@FL bound to the peptidoglycan on the surface of the bacterial cell wall,thus forming a“sandwich”structure.Then,magnetic separation techniques were used to recover bacteria from complicated food matrices.UIO-B（OH）₂@FL is unstable in alkaline solutions and releases fluorescein with luminol via a CRET mechanism,leading to a change in chemiluminescence color from blue to green.Using 3D printing technology,a portable device with a smartphone as a signal reader was prepared to perform rapid quantitative detection of S.aureus in the range of 10-10⁷ CFU/m L,and the LOD was 1.44CFU/m L.The POCT sensing platform offers excellent immunity to interference and allows for the immediate quantification of bacteria in tap water and milk samples with recoveries ranging from 88.8%to 109.4%.In addition,based on the photothermal conversion capability of Fe₃O₄@Van,the inactivation efficiency of captured S.aureus is as high as 96.76%by generating heat under NIR laser irradiation.The integrated detection and inactivation platform allows for the capture and quantification of pathogenic bacteria in complex food matrices and is also expected to be used for the early diagnosis and treatment of bacteremia.