Construction And Application Of Photo-activated Antibacterial Nanomaterials

With the increasingly serious bacterial infection,the massive use of antibiotics has caused serious problem of multi drug resistance(MDR)of bacteria.Therefore,it is particularly urgent to develop new antibacterial materials.Nanomaterials,as a rising star,have attracted wide attention because of their special superiority against multi drug resistance of bacteria.The main work of this paper is to construct photo-activated antibacterial system based on nanomaterials and exhibit effective antibacterial activity under near-infrared or natural sunlight.The detailed works are introduced as follows:1.First we modify dopamine with carbon-carbon double bond(DMA)using substitution reaction.Then water soluble copolymer of DMA and N-isopropyl acrylamide(NIPAM)are synthesized by radical polymerization.With the help of catechol unit fragment of copolymer,ferromagnetic oxide nanoparticles are modified with copolymer and dopamine with a proper proportion.We construct functional nano-system having photothermal effect,thermosensitivity and magnetic properties which is named as Fe3O4-PDA-Poly,and we characterize physical and chemical properties of polymer and nanoparticles by means of 1H nuclear magnetic resonance(NMR),transmission electron microscopy(SEM),fourier transform infrared spectrometer(FTIR),dynamic light scattering(DLS)and other methods.The temperature responsiveness of the nanomaterials and the adsorption/release behavior of bacteria are explored under low temperature and high temperature.After irradiating by near-infrared laser,Fe3O4-PDA-Poly show a strong photothermal effect,and the antibacterial tests prove that the nanomaterials have excellent antibacterial activity.After three cycles,the antibacterial activities remain high.This research provides a new idea for functional modification of nanoparticles and is expected to be applied in the treatment of wound infection.2.The silicon nanowire arrays are prepared as substrate and dopamine molecules are deposited on the surface of the silicon nanowire arrays.Then we utilize the weak reducing property of polydopamine to simultaneously reduce the tetrachloroauric acid solution and the silver nitrate solution at the appropriate temperature to obtain the silicon nano wire arrays modified with gold and silver alloy nanoparticles(SN-Au/Ag).We characterize the physical and chemical properties of the materials by means of scanning electron microscopy(SEM),X-ray photoelectron spectroscopy(XPS)and visible light absorption spectrum(vis).Then we explore the antibacterial properties of the alloy nanomaterials under simulated sunlight through colony counting assay and live/dead staining assay.The results show that SN-Au/Ag can kill bacteria with high efficiency under simulated sunlight in times of the order of a few minutes,and this is achieved through synergism between photothermal and photocatalytic effects.Moreover,the SN-Au/Ag material can be "recycled" without loss of bactericidal activity and SN-Au/Ag has no obvious toxicity to L929 cells.The most surprising thing is that SN-Au/Ag still exhibits bactericidal efficiency close to 99.9%in natural sunlight.This method provides a new idea for the construction of a new and efficient antibacterial system,which is expected to be applied in sewage treatment,air purification and wound infection healing.In summary,nanomaterials with photo-activated antibacterial activity are prepared by combining nanomaterials with optical therapy.We modify magnetic nanoparticles with dopamine-containing polymers and nanomaterial exhibit high antibacterial efficiency under near-infrared(NIR)irradiation;gold-silver alloy nanoparticle-modified silicon nanowire arrays(SN-Au/Ag)are prepared by in situ co-reduction of the surface of silicon nanowire arrays with tetrachloroauric acid(HAuCl4)and silver nitrate(AgNO3).It is shown that SN-Au/Ag can kill bacteria with high efficiency under sunlight in times of the order of a few minutes.With the development of science and technology,nanomaterials will play a more important role in the fight against drug resistant bacteria.