| Medical-device-associated infections caused by adhered pathogenic bacteria on materials surface have greatly challenged the human health.Antibiotics,as one of the most important discoveries in modern medicine,have made significant progresses in combating bacterial infections and protecting human health.However,their efficacy experienced inability to kill multi-resistant bacteria due to the development of antibiotic resistance.As an alternative,cicada wing-inspired nanostructures based mechanobactericidal surfaces exhibit excellent antibacterial properties.Differing to conventional biocides,those nanostructured surfaces can physically kill adhered microorganisms via mechanical rapture of bacterial cells by nano-pillar arrays without triggering any potential antimicrobial resistance(AMR),which may hold promise in restraining or addressing the global epidemic of multi-resistant bacteria caused by the overuse of antibiotics.Nevertheless,since this bactericidal performance is based purely on non-specific mechanical stresses exerted by the bio-inspired nanostructure on the bacterial membrane,the bacteria will rupture and die only when this non-specific force is greater than the strain that the bacterial cell membrane can withstand.As a result,most(especially polymer-based)nanostructures are difficult to achieve rapid,efficient and broad spectrum bactericidal performance at present.In addition,the rough nanostructured surface can be readily contaminated and dead barerial cells may accumulate on this surface,which can shield the structure and further impair the antimicrobial activity.As a result,it is difficult to achieve long-term and repeatable antibacterial performances.Based on the mechanical bactericidal principles inspired by naturally occurring nanostructures,this work aims to develop purely physical antimicrobial strategies to combat the problem of multidrug-resistant bacteria caused by the excessive use of chemical biocides,while achieving rapid,efficient,broad-spectrum and long-acting antimicrobial properties.Inspired by the nanosture of cicada wing and micro/nanostructure of lotus leaf,we have designed and fabricated photothermal effect based synergistic antibacterial surface,lotus leaf-inspired micro/nano-structure based dualfunctional antibacterial surfaces and polymer@nanostructure based thermo-responsive multifunctional antibacterial surface.The internal relationships between antibacterial performances and surface morphology characteristics,photothermal conversion properties,wettability and polymer themo-responsive molecular conformation property were investigated respectively.The main research contents and conclusions are as follows:(1)Photothermal effect based synergistic antibacterial surface: After analyzing the morphological characteristics of the cicada wing surface,a simple template replication method was used to prepare the polymer-based biomimetic nanostructured surface.Subsequently,to overcoming disadvantages(including low bactericidal efficiency,slow bactericidal speed,and inability to kill broad-spectrum bacteria)of sole mechanobactericidal based surface,the photothermal TA/Fe nanocoating was successfully anchored on the surface of the biomimetic nanostructure taking advantages of the simple and rapid film forming mechanism of TA/Fe complex.After being irradiated for only 3 minutes,the hybrid nanostructured surface presented excellent bactericidal activities with more than 99% reduction for both gram-positive Staphylococcus aureus and gram-negative Pseudomonas aeruginosa.(2)Antibacterial performances of natural lotus leaf: In this study,for the first time,we proposed and confirmed that the lotus leaf,well known for its superhydrophobicity and anti-biofouling properties,demonstrated remarkable mechano-bactericidal activity.While the excellent superhydrophobic property of the lotus leaf surface can resist most of the contaminations and bacteria in the initial stage,those tenacious bacteria that managed to be in touch of the surface were killed completely.The further investigation of the bactericidal mechanism demonstrated that the chmical components are not responsible for the bacteria death which indirectly reflected the physical bactericidal property of the surface.Benefiting from the purely physical synergistic antibacterial strategy,lotus leaf provides a new inspiration for constructing long-term and efficient structure based antibacterial platforms without causing risks of AMR.(3)Micro/nano-structure based dual-functional antibacterial surfaces: Inspired by the relationship between the pure physical antibacterial mechanism and the structural morphology of lotus leaves,a biomimetic micro/nano-structured surface was designed and constructed a combination of plasma etching and hydrothermal reaction,and subsequently a chemisorption process was performed to obtain the superhydrophobic surface.The analysis of the relationship between different structural morphology scales and surface wettability showed that compared with the single-scale surface,the hierarchical micro/nano-structured surface demonstrated the best superhydrophobic effect with ultra-high contact angle(> 174°)and extremely low roll-off angle(< 1°).Benefiting from this excellent superhydrophobic property,the hierarchical micro/nanostructured surface could withstand a continuous contamination of bacterial medium for24 h,and even a small amount of bacteria adhered to the surface can be effectively killed.This study shows that the realization of the dual-function is sequential,and the basis of their construction is synchronized.Thus,there is no mutual interference and weakening between those two antibacterial functions.This work provides a new idea for the construction of a purely physical,long-acting non-drug resistant antibacterial surface.(4)Polymer@nanostructure based thermo-responsive multifunctional antibacterial surface: In order to realize the active and controllable release of dead bacteria and contaminations on the mechano-bactericidal surface,poly(Nisopropylacrylamide)which can change its molecular conformation in response to the temperature was introduced onto the nanostructure surface via surface-initiated photoiniferter-mediated polymerization(SI-PIMP).Thus,the multifunctional PNIPAA@Zn O nanostructured surface was successfully fabricated.The multiple antibacterial functions can be readily regulated through the change of temperature.The hybrid nanostructured surface presented excellent antibacterial adhersion property below the lower critical solution temperature(LCST).The active bactericidal pillars can be exposed readily just through increasing the temperature above its LCST,due to the polymer chain transforms to collapsed and contracted conformation at this temperature,and 99% of bactericidal efficiency could be realized.The adhered dead bacteria and debris could be effectively removed from the surface via lowering the temperature below its LCST.By precisely controlling the thickness of the PNIPAAm molecular chain and correctly using its conformational changes at different temperatures,this work not only retains the unique mechanical bactericidal property of the structure,but also realizes the active and controllable bacterial cells release function.This study provides a new reference for constructing multi-functional antibacterial surface with intelligent,long-lasting and reusable properties... |
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