Construction And Antibacterial Application Of Visible Light-Responsive Nitric Oxide Polymer Delivery Vehicles

Nitric oxide(NO)is a kind of diatomic free radical with high activity.It has a wide range of physiological activities and can be used in the treatment of many diseases such as immunomodulatory,cardiovascular disease,tumor,bacterial infection,and so on.However,NO has a short half-life and its physiological effects are highly dependent on its concentration.Therefore,local controlled delivery of nitric oxide is of great significance for improving the therapeutic effect of nitric oxide and reducing systemic toxicity.Up to now,many exogenous nitric oxide donor molecules have been developed.Of these,N-diazeniumdiolate(NONOate)and S-nitrosothiols(SNO)derivatives are most widely investigated,which are difficult to achieve the expected therapeutic effect due to poor stability and premature leakage under physiological conditions.In this paper,a variety of NO-releasing polymers were prepared by the direct polymerization of Nnitrosoamine-based monomers,and their applications in antibiofilm and antibacterial were explored.The content of this paper is divided into three major sections.1.Synthesis of N-nitrosoamine NO donor(CouNO)as a polymerizable monomer based on 7-amino-4-methyl coumarin,and fabricated NO-releasing polymer through the direct polymerization.The prepared amphiphilic polymers spontaneously selfassemble into micellar nanoparticles capable of loading Cip within the hydrophobic core.Although the process of light-triggered NO release did not dissociate the micellar nanoparticles,a drastic polarity switch occurred,leading to the co-release of Cip and NO.In addition,visible light-mediated NO release was accompanied by a significant increase in fluorescence emission,enabling self-reporting NO release.We demonstrated that the corelease of NO and Cip could more efficiently eradicate bacterial biofilms and kill bacteria.2.NO releasing monomer molecules containing N-nitrosoamine moieties were synthesized by using tetraphenylethylene(TPE)with the property of aggregationinduced emission(AIE)properties as the visible light absorbing antenna.The direct polymerization of the NO-releasing monomers leads to the formation of an amphiphilic diblock copolymer named PTNO,which can self-assemble into micellar nanoparticles in aqueous solutions capable of loading hydrophobic therapeutic agents such as ciprofloxacin(Cip)within the micelle cores.Under visible light irradiation,the photosensitive N-nitrosoamine moieties were cleaved with the release of NO radicals via the homolysis of N-NO bonds,while the resulting aminyl radical could abstract hydrogen atoms from the surrounding environment.NO release led to the recovery of the fluorescence emission of TPE,which can thus be used for reporting the NO release process in situ.The as-formed intermediates then underwent spontaneous 1,6elimination reactions with the release of primary amines.The in situ formed primary amines further took part in inter/intrachain aminolysis reactions within the micellar cores,thereby crosslinking the micellar nanoparticles and driving a hydrophobic-tohydrophilic transition,which allowed the release of encapsulated payloads.Upon visible light irradiation,the corelease of NO and Cip was achieved,exerting a synergistic antibiofilm effect against Pseudomonas,aeruginosa(P.aeruginosa)biofilms.3.A series of NO donor based on 7-amino-4-hydroxymethyl coumarin and palladium(Ⅱ)tetraphenyltetrabenzoporphyrin(PdTPTBP)photosensitizer were synthesized.In the presence of PdTPTBP,NO donor can release NO under 630 nm red light irradiation,achieving stoichiometric and self-reported release of NO.The mechanism of NO release triggered by red light was proved to be photoredox catalysis by combining experiment and theoretical calculation.For the first time,we revealed that PdTPTBP photosensitizer could be used as a photoredox catalyst as well.To demonstrate the potential biomedical applications,NO-releasing micelles were fabricated through the incorporation of PdTPTBP and CouN(NO)-R derivatives into micelle cores.The NO release with the generation of CouN(H)-NO2 moieties within micellar cores led to the fluorescence turn-on.In addition,the encapsulated payload such as ciprofloxacin(Cip)was released under 630 nm light irradiation,enabling the corelease of NO and Cip.The resultant NO-releasing micelles cannot only disperse P.aeruginosa biofilms but also eradicate bacterial pathogens in vitro.Further,we confirmed that the NO-releasing micelles with low cytotoxicity to normal mammalian cells could efficiently treat bacterial infection in a cutaneous abscess model,exhibiting excellent antibacterial performance and accelerating wound healing.