Smart Antibacterial Surfaces With Switchable Bacteria-killing And Bacteria-releasing Capabilities

The attachment of pathogenic bacteria and subsequent biofilm formation on material surfaces pose a series of adverse eonsequences,xvhich eause serious problems in both human healthcare and industrial applications.Endowing material surfaces with antibacterial properties to prevent bacterial attachrIlent and proliferation is an effective way to solve these problems.However,the traditional strategies for construction of antibacterial surfaces are mainly focused on killing the attached bacteria on the surface.while ignoring the secondary contaminations caused by the accumulation of dead bacteria and debris on the surface.Aiming at this issue,researchers proposed a promising“kill-release”strategy and applied it to prepare so-called smart antibacterial surfaces.Such surfaces can kill bacteria attached to the surface and then release dead bacteria and other debris under an appropriate stimulus to give a clean surface.thereby maintaining effective long-term antibacterial activity.In this thesis,we fabricated a series of smart antibacterial surfaces with switchable bacteria-killing and bacteria?releasing capabilities based on this“kill-release”strategyThe detailed research contents are as follows:(1)A smart antibacterial surface capable of step?ise switching the bactericidal function and bacteria-releasing function was fabricated by combing stinuli-responsiveness of polymer brushes and topographic effect of nanomaterials.Firstly,silicoii nanowire arrays(SiNWAs)were modified with a PH-rcsponsive polymer,poly(methacrylic acid)(PMAA)via surface-initiated polymerization.A large number of lysozyme with anlibacrerial activity were then loaded into this surface under an acidic pH through the combination of the pH-responsivity of grafted PMAA chains and the enhanced local topographic effect of SiNWAs.The resulting surface could not only release a majority of the loaded lysozyme to kill the bacteria both suspended in solution and attached to the surface under a neutral pH.but also release the dead bacteria to keep surface clean under a basic pH.Moreover,both the pH-responsive binding/release of lysozynie and the killing/releasing of bacteria were repeatable(2)A supranolecular smart antibacterial surface with photoresponsive and switchability between bactericidal function and bacteria-releasing function was fabricated by the combination of self-assembly and host-guest interaction.Firstly,a mixed monolayer containing azobenzene(Azo)group was prepared on gold surface by Au-S interaction;the Azo groups then served as anchors for incorporation of a biocidal?-cyclodextrin(?-CD)derivative containing seven quaternary ammonium salt groups(CD-QAS)via host-gust interaction between Azo and ?-CD.Taking the advantage of excellent bactericidal activity of CD-QAS,the resulting surface could efficiently kill the attached bacteria.Under UV light irradiation,the Azo groups switched from trans form to cis form,resulting in the dissociation of Azo/CD-QAS complex and the removal of dead bacteria from the surface.Moreover,after one kill-and-release cycle,the original surface could be regenerated for reuse by irradiation with visible light to recover the Azo trans form for reincorporation of fresh CD-QAS,achieving repeatable bactericidal function and bacterial-releasing function(3)A universal approach for fabrication of multifunctional antibacterial surfaces was developed by the combination of layer-by-layer(LBL)deposition and host-guest interaction.Firstly,a polyelectrolyte multilayered film containing adamantane(Ada)groups was prepared by LBL deposition;the Ada groups on matrix then served as anchors for the incorporation of a biocidal CD-QAS via host-gust interaction between Ada and ?-CD.Because of the excellent contact-based bactericidal activity of CD-QAS.the resulting surface exhibited strong biocidal activity to kill more than 95%of attached bacteria.Moreover,introduction of-sodium dodecyl sulfate(SDS)could dissociate the host-guest interaction between Ada and CD-QAS and thus release almost all the dead bacteria from surface.This is a facile and universal method and it could be applied to virtually any substrate regardless of surface properties.More importantly,the multifuntionality of surface could be achieved via co-incorporation of other functional 13-CD derivatives with CD-QASIn summary.a series of smart antibacterial surfaces with switchable "kill-release"capability were fabricated by various surface modification methods including surface initiated polymerization,self-assembly,LBL deposition and host-guest interaction These surfaces can not only kill the attached bacteria efficiently.but also release the dead bacteria and other debris to maintain a long-term antibacterial activity under an appropriate stimulus.The results of this thesis have important fundamental research value and provide new ideas and methods for the construction of new antibacterial surfaces,showing potentials for diverse biomedical applications such as medical instruments and catheters.