Preparation And Antibacterial Properties Of Photoresponsive Metal-organic Framework Materials

The skin is an important barrier to prevent bacteria from entering the human body.However,if the skin is damaged,bacteria can easily invade the human body from the wound site and form colonies,which can lead to wound infection and hinder the wound healing process and even lead to complications.Therefore,how to kill pathogenic bacteria and promote wound healing is an urgent problem to be solved in clinical medicine.The main antibacterial agent for treating infected wounds is still antibiotics,but with the abuse of antibiotics,bacteria have developed resistance and become more difficult to remove.Therefore,it has become an urgent task to develop novel and efficient antibacterial agents and antibacterial strategies to solve the increasingly serious infection of pathogenic bacteria,including multidrug-resistant bacteria.In recent years,as a new and rapidly developing nanomaterial,the emergence of metalorganic frameworks(MOF)materials has attracted great attention.Scientists have found that MOFs can be used as antibacterial agents,among which MOFs with photocatalytic and photothermal properties have received more attention.The photodynamic therapy(PDT)of MOF refers to the use of an external light source to irradiate MOF with photocatalytic effect to produce a variety of reactive oxygen species(ROS)to kill bacteria.However,the PDT efficiency of pure MOF photocatalyst is too low due to the wide band gap,weak visible light absorption capacity,and the fast recombination rate of photogenerated electrons and cluster center.Therefore,in order to improve the PDT efficiency of MOF,the photocatalytic effect of MOF must be improved.Similarly,the photothermal therapy(PTT)of MOF refers to irradiating MOF with photothermal effect with an external light source to generate high temperature for sterilization.However,to achieve higher antibacterial efficiency,high ROS production rate or higher temperature is often required,while excessive ROS or high temperature will cause great damage to normal cells and tissues.Therefore,for antibacterial in vivo,the synergistic of PDT and PTT is generally adopted for sterilization,so that efficient and rapid sterilization effect can be achieved at a low temperature and a certain amount of ROS.Based on this,it is of great significance to prepare MOF materials with light-responsive rapid sterilization under the condition of ensuring biosafety.Aiming at how to improve the photoresponsive antibacterial performance of MOF,the following three design ideas were proposed in this paper.We designed and fabricated MOF materials with controllable photocatalytic properties and photothermal effects,and investigated their antibacterial properties in vitro and in animals:(1)Project 1: The antibacterial system of PB-PCN-224 was constructed.When irradiated with the 660 nm red light,PCN-224 increased the transfer rate of electrons generated in PB,which delayed the recombination rate of electron hole pairs in PB-PCN-224 system,thus improving the photocatalytic effect of PB-PCN-224 and increasing the ROS production rate of PB-PCN-224.At the same time,the introduction of PB makes PB-PCN-224 had good photothermal effect under the irradiation of 660 nm light.The synergistic of PDT and PTT made the antibacterial rate of PB-PCN-224 against Staphylococcus aureus and its biofilms up to 99.84% and 99.3%,respectively.Meanwhile,iron and zirconium ions released from PBPCN-224 composites were biocompatible and their cytotoxicity was negligible.More importantly,in vivo experiments had shown that PB-PCN-224 could speed up the healing of bacteria-infected wounds.(2)Project 2: MOF constructed by porphyrins as organic ligands has been widely used in antibacterial treatment due to its photocatalytic effect.However,porphyrins are difficult to degrade in vivo and remain in large quantities,which may cause porphyria in human body.Therefore,on the basis of the previous scheme,in this scheme,UIO-66-TCPP MOF was constructed by using a UIO-66 MOF which was easy to synthesize and high stability to load a small amount of porphyrin.Then we synthesized the core-shell double MOF heterostructure named PB@MOF using PB MOF as the core and porphyrin-doped UIO-66-TCPP MOF as the shell.Because the structure contained both porphyrin and PB,PB@MOF had both PTT and PDT properties.Through the synergistic effect of photothermal and photodynamic,the dual MOF structure could achieve the rapid bactericidal effect of eradicating more than 99% of Staphylococcus aureus and Escherichia coli within 10 minutes under the dual light irradiation of 808+660 nm.In addition,trace iron and zirconium ions in PB@MOF could trigger the immune system to promote wound healing,which was expected to achieve rapid treatment and environmental disinfection of bacterial infected wounds by PB@MOF.(3)Project 3: In order to further solve the problem that MOF composed of porphyrins and its derivatives may be degraded in vivo,resulting in porphyrins remaining in vivo,we constructed another NH2-MIL-125 MOF with good biocompatibility for photocatalytic antibacterial treatment.In order to improve the photocatalytic efficiency of NH2-MIL-125,we introduced two-dimensional material graphene oxide(GO)and noble metal platinum(Pt)nanoparticles into the NH2-MIL-125 system to construct NH2-MIL-125-GO-Pt ternary heterojunction.GO,as an excellent conductor,carried away the photogenic electrons produced in NH2-MIL-125.At the same time,Pt nanoparticles could form schottky heterojunction with NH2-MIL-125,and further guided away the photogenic electrons in NH2-MIL-125.Therefore,the doping of GO and Pt nanoparticles could effectively separate the electron hole pairs generated in NH2-MIL-125,thus improving the photocatalytic efficiency of NH2-MIL-125-GO-Pt system.With the improvement of photocatalytic efficiency,the yield of ROS also increased.At the same time,the doping of GO and Pt also endowed NH2-MIL-125 with good photothermal effect.Therefore,under the synergistic effect of photothermal and photocatalysis,the NH2-MIL-125-GO-Pt composite had high antibacterial efficiency,and the sterilizing rate opposed to Staphylococcus aureus and Escherichia coli were as high as 99.94% and 99.12%,respectively.This work brings new insights into the rapid disinfection of environments with pathogenic microorganisms using NH2-MIL-125-based photocatalyst materials.