Construction Of Nano-delivery System And Its Application In Anti-drug Resistance Bacteria

Bacterial infections are becoming one of the major threats to human health,and the threat will persist for a long time.Although antibiotics provide a good strategy for the successful treatment of bacterial infectious diseases,the increase in drug-resistant microbial infections and the decline in the class and number of new antibiotics have made bioengineering agents difficult to use in traditional therapies.With the deepening of nanomedicine research,it has been found that nanomedicine can evade the mechanism of bacterial resistance,which is one of the ideal means to fight drug-resistant bacterial infection,and provides a new strategy for the development of antibacterial drugs.According to different types of Gram-positive/negative bacteria,a variety of intelligent nano-delivery systems have been designed to deliver drugs or antigens to achieve multi-faceted treatment of bacterial infections,providing new ideas for solving bacterial drug resistance.The main research proposals are as follows:1.p H-responsive metal-organic framework deliver antibiotics for combination therapy of methicillin-resistant Staphylococcus aureus infectionsIn this section,we investigated a novel approach to deliver antibiotics synergistically in the treatment of bacterial infections based on a light-responsive drug-releasing ZIF-8.This method encapsulated the light-responsive 2-nitrobenzaldehyde（o-NBA）and rifampicin（RFP）in ZIF-8 to form a nano-antibacterial agent（RFP&o-NBA@ZIF-8）.The special structure of the ZIF-8 carrier can avoid drug leakage and achieve controlled drug release.o-NBA can generate H⁺under UV light（λ=365 nm）,which further induce the degradation of ZIF-8 to release RFP and Zn²⁺,and realize the synergistic antibacterial of antibiotics and metal ions to increase the sensitivity of bacteria to antibiotics.Antibacterial experiments showed that 10μg/m L RFP&o-NBA@ZIF-8 had a synergistic antibacterial effect of 98.9%against MRSA under UV light.Animal experiments showed that RFP&o-NBA@ZIF-8 can inhibit bacterial infection and accelerate wound healing under irradiation,and show good biocompatibility.This study provides a new idea for the intelligent drug delivery system of MOF against bacterial infection.2.Exotoxin-triggered nanoliposomes deliver antibiotics and present toxin vaccines for synergistic therapy of methicillin-resistant Staphylococcus aureus infectionsIn this section,we investigated a nanoliposome with targeted and controlled drug release upon endogenous stimuli.This strategy is to load Ca O₂ and RFP into a PCM and encapsulate a phospholipid coating on the outer layer to form nanoliposomes（RFP-Ca O₂@PCM@Lec）.The melting point of PCM is 35.2-38.3°C,and it will change from solid to liquid at physiological temperature,which provides a prerequisite for drug release.Nanoliposomes trapped pathogenic bacterial exotoxins in the body,causing their own phospholipid bilayers to be pored by toxins.Water molecules entered the nanoliposomes through the pores and reacted with Ca O₂ to generate H₂O₂,which was decomposed into O₂to drive the drugs release for the treatment of bacterial infections.Antibacterial experiments showed that the antibacterial effect of RFP-Ca O₂@PCM@Lec on MRSA reached 98.2%.At the same time,nano-liposomes formed a nanovaccine after trapping toxins,which can stimulate the body to trigger a specific immune response.Experiments showed that nano-toxin vaccine could stimulate germinal center B cells to mature and produce specific antibodies.Antibodies have good exotoxin neutralization ability and reduce toxicity in vivo.This study provides a new strategy for the multi-faceted treatment of bacterial infections with nanoliposomes,and lays a theoretical foundation for immunotherapy of bacterial infections.3.Photothermal responsive metal-organic framework deliver nitric oxide for targeted therapy of antibiotic-resistant Pseudomonas aeruginosa infectionsIn this section,we investigated a MOF-based nanocarrier with NIR-triggered release of NO for targeted therapy of P.aeruginosa infection.Since maleimide（Mal）can recognize bacterial T4P pili,SNP@MOF@Au-Mal releases NO under NIR irradiation,and the inorganic photosensitizer gold nanoparticles can generate ROS to achieve synergistic antibacterial of gas and ROS.In situ generation of high concentrations of gas can promote the transfer of more NO and its derivatives（N₂O₃,ONOO^-）to bacteria,thereby significantly improving the antibacterial effect.Antibacterial experiments showed that SNP@MOF@Au-Mal could precisely release NO at the infection site under NIR illumination,and its antibacterial efficiency was 97.7%.Meanwhile,NO can further regulate macrophage polarization,induce angiogenesis,promote growth factor secretion and cell migration to accelerate wound healing.The study demonstrates that precision gas therapy has great application potential in the treatment of drug-resistant bacterial infections.4.Outer membrane vesicle-coated nanovaccine delivery antigen to enhance immunotherapy for drug-resistant Pseudomonas aeruginosa pneumoniaBacterial outer membrane vesicles（OMVs）can serve as ideal antigens for bacterial immunotherapy due to their non-replicable bilayer structure and containing a large number of virulence proteins.In this section,we successfully constructed the LPS@DMON@OMV nanovaccine with P.aeruginosa-OMV as the antigen and lipopolysaccharide（LPS）as the adjuvant,and applied it to enhance the immunotherapy of bacterial pneumonia.In vivo studies have shown that nanocarriers can efficiently present antigens to dendritic cells（DCs）and induce rapid activation and maturation of DCs.The specific antibody titer produced by the nanovaccine immune response is 180 times higher than that of free antigen immunization,and it can also induce more virulent CD8⁺T cells,thereby eliminating bacteria in the body through humoral and cellular immunity.The nanovaccine also stimulated the mice to form an immune memory that was retained for up to three months to prevent the risk of bacterial reinfection.Bacterial OMVs-coated nanovaccine provides a new strategy for designing effective antibacterial vaccines.In summary,this paper achieves multi-faceted treatment of drug-resistant bacterial infections by designing a variety of intelligent nano-delivery systems to deliver drugs or antigens,which provides a theoretical basis for nano-drug antibacterial and a new method for the treatment of bacterial infections.