Antibacerial Coating And Microsphere Based On Schiff Base Bond

Microbial contamination is one of the public health safety problems that need to be solved urgently.Because the overuse of antibacterial drugs has led to the emergence of many resistant bacteria,it is a hot spot for antibacterial materials to develop new antibacterial strategies to control the excessive application of antibacterial drugs.The objective of this project is to utilize the dynamic response properties of Schiff base bonds,introducing antibacterial peptides(AMPs)with side chain amino groups and antibiotics(Tob)to enhance the antibacterial properties of the system,and the formation of Schiff base bonds limits the release of the antimicrobial peptides and the antibiotics.When the growth of bacteria causes the acidity to decrease,the Schiff base bond will respond to the breaking bond,releasing the antibacterial substance,which in turn acts as a bactericidal effect.First,a pair of aldehyde-based benzoic acid diethylene glycol(FD)and a aldehyde benzoic acid borneol ester small molecule(BF)were designed and synthesized.The GC-FD-AMPs-BF(GFAB)intelligent response antibacterial coating was constructed by layer-by-layer self-assembly method using chitosan(GC)as the substrate and Schaff base bond formation.The successful synthesis of GFAB materials was confirmed by UV spectroscopy.ZOI experiments have shown that BF can achieve the control of the release of antimicrobial peptides,but due to the strong hydrophobicity of the selected AMPs,the stability of the Schiff base bond is increased,resulting in the material does not respond effectively to the concentration of bacteria.A simplified system for the construction of AMPs-BF(APB)materials yielded similar results.In order to adjust the hydrophilicity of the system,GFTB materials were constructed by using hydrophilic Tob instead of AMPs.UV characterization confirmed the successful synthesis of GFTB materials.ZOI experiments show that due to the excessive hydrophilicity of the system,the assembly integrity and controllability of the system are poor.The antibacterial experiment of the coated modified catheter confirmed that the material is responsive to the concentration of the bacteria and can inhibit the growth of 106 CFU/mL bacteria.pH stability studies have shown that the responsive bactericidal ability of the material comes from the acid responsiveness of the Schiff base bond.The simplified system assembled the Tob-BF(TB)material with results similar to those of the GFTB material.Further,TBF microspheres were assembled by sedimentation of Tob and BF.The successful assembly of TBF microspheres was confirmed by UV spectroscopy,SEM and TEM characterization.Its drug loading rate is 22.26%and the encapsulation efficiency is 5.56%.With obvious pH responsiveness,the cumulative release at 72 h can reach 79.88±1.4%at pH 5.Through the experiment on the concentration of bacteria,it can be proved that TBF does not have the bactericidal function in the early stage of bacterial growth.When the concentration of bacteria reaches the response threshold of Schiff base bond,TBF breaks and sterilizes.The most suitable response range of TBF is 80-125?g/mL.