Study Of All-biobased Superhydrophobic And Photodynamic Synergistic Antibacterial Polylactic Acid Surfaces

The problem of nosocomial infections caused by bacterial growth on material surfaces is a serious threat to public health safety.Currently,antibacterial strategies are mainly divided into anti-bacterial adhesion and bactericidal.Both strategies are effective,but have their own limitations.Anti-adhesion strategy can effectively reduce the initial bacteria adhesion,but once a little bacteria adhered,it will be difficult to stop the subsequent bacteria from multiplying.Bactericidal strategies can effectively kill bacteria,but antibiotic biocides are prone to bacterial resistance.There is an urgent need for an effective antibacterial strategy that can inactivate bacteria without triggering bacterial resistance.Polylactic acid（PLA）is a bio-based biodegradable material with promising applications in biomedical and food packaging fields,but its inherent poor antimicrobial properties and toughness limit its scope of application.To overcome these problems,a functional PLA surface with synergistic effect of superhydrophobic antibacterial adhesion and photodynamic sterilization was designed,and the wettability,self-cleaning properties,microscopic morphology,roughness and antibacterial properties of the surface were investigated.Based on this,PLA was toughened and modified with plant oil-based plasticizer acetylated mono-diglyceride fatty acid ester（AMG）,and the mechanical properties,thermal behavior,flow properties,permeability,mobility and wettability of the modified material were investigated.Then the tough PLA surface was endowed with superhydrophobic and photodynamic synergistic antibacterial functions.Study of antibacterial PLA surfaces with synergistic superhydrophobicity and photodynamic.Functional PLA surfaces with superhydrophobic and photodynamic synergistic antibacterial properties were prepared by a simple and easy non-solvent-assisted induced phase separation process and using a completely non-toxic photosensitizer chlorophyll.The contact angle of the prepared PLA surface was152°at a non-solvent to good solvent ratio of 9:10,when the microscopic morphology was a layered structure consisting of similar microspheres and nanofolds.The superhydrophobic surface has low adhesion and the introduction of chlorophyll does not affect the surface micro/nano structure and superhydrophobic properties.The synergistic antibacterial PLA surface has characteristic peaks of chlorophyll and characteristic elements（N and Mg）,demonstrating successful immobilization of chlorophyll.The bactericidal performance was dependent on the production of reactive oxygen species（ROS）by chlorophyll under visible light irradiation（650 nm,10 W）.The chemical probe 1,3-diphenylisobenzofuran（DPBF）was used to demonstrate the production of ROS.Bacterial experiments showed antibacterial adhesion efficiencies of up to 60%for superhydrophobic samples and 99.8%for synergistic antibacterial PLA surfaces.Subsequent antibacterial experiments on PLA masks by spray method showed antibacterial efficiency up to 97.91%.Study of all-biobased tough antibacterial PLA surfaces.A melt blending process was used to toughen and modify PLA with plant oil-based plasticizer AMG as a plasticizer,followed by solvent-assisted phase separation and chlorophyll fixation process to prepare a fully bio-based ductile PLA antibacterial surface.With the increase of AMG ratio,the elongation at break increased while the tensile strength decreased and the impact strength slightly increased.The addition of AMG led to a decrease of T_g and a slight decrease of thermal stability of PLA,which macroscopically showed an increase of toughness and a decrease of strength and stiffness,as well as increase of the permeability of the material.Mobility tests showed that the sample films were suitable for using in water,weakly acidic products and lower concentration of alcohol-based products,and not suitable for packaging greasy products.The best hydrophobic performance was achieved when the AMG content was 7.5%and the ratio of bad solvent to good solvent was 9:10,and the microscopic morphology was a microsphere stacking structure.The stretching vibration peaks of C=C and CH₂ indicated the successful immobilization of chlorophyll on the ductile PLA surface.The decrease of the maximum absorption peak of DPBF under visible light irradiation indicates the production of ROS.The bacterial experiments showed that the number of bacteria on the surface of the synergistic antibacterial samples was the lowest due to the synergistic effect of antibacterial adhesion and photodynamic sterilization.