| Chitosan is obtained by deacetylation of chitin,and one of its important biological activities is antibacterial activity.However,chitosan has some problems in antibacterial application,such as poor water solubility and no antibacterial effect after film formation.In order to solve these problems,a series of modifications have been made to chitosan,one of which is related to schiff base.In this study,schiff base dynamic covalent bond and borneol micromolecule were used to form composite materials,which could realize the antibacterial effect of controlling fungus adhesion and releasing micromolecule by surface chiral stereochemical structure at the same time.The borneol molecule has a large cage-shaped hydrophobic group itself,and has the function of stabilizing schiff base,so that the borneol molecule is not easy to break in aqueous solution.Therefore,the pyridine aldehyde structural unit is designed as a connecting segment,and the positive charge can increase the hydrophilic effect of the structural unit.At the same time,the binding stability of schiff base can be reduced by the electron withdrawing action,so that the schiff base can be easily broken and the stimulation response to bacteria can be realized.Because pyridine aldehyde structural unit shows positive electricity,it also can absorb all kinds of bacteria which are usually negative electricity,to inhibit the synthesis of liposome in the membrane and cell apoptosis.The specific process is as follows:through the first step esterification of borneol and bromoacetyl bromide,borneol ester can be obtained,which is recorded as BBR;Then BBR reacts with tetracyridine formaldehyde to generate pyridine ring with positive charge and aldehyde group,which is recorded as BN;The third step is that BN reacts with the amino group of the chitosan to form schiff base,where borneol is connected to the chitosan in the form of a dynamic covalent bond mat.And the borneol composite chitosan material is recorded as BNCN.BNCN material was modified 1-4 layers by LBL,and several antibacterial experiments were designed,such as jailbreak experiment,bacteriostatic circle experiment and plate counting experiment.The results showed that BNCN material could achieve antibacterial adhesion and release small molecules to kill bacteria.The material combines natural high molecular chitosan and small molecular borneol with unique stereo chemistry characteristics through a dynamic schiff base bond.Starting from the structure of the material,we believe that the material can achieve the antibacterial effect of three layers.Bacteria respond to the unique stereochemistry characteristics of borneol and do not grow on the surface of the material at the initial stage of antibacterial;When a small amount of bacteria are passively adhered to the surface of the material,the dynamic covalent bond of the schiff base of the material can respond to the stimulation of the bacteria,and meanwhile,the positive charge carried by the material can promote the breakage of the schiff base bond,so that the dynamic covalent bond is broken at this time,the bactericidal borneol micromolecule is released,and the bacteria are killed;When a large amount of bacteria grow on the surface of the material,the material is completely disintegrated into two parts,namely chitosan and tetrapyridyl aldehyde borneol ester,and the chitosan and the tetrapyridyl aldehyde borneol ester are sterilized together.Then,in order to further prove the formation of dynamic covalent bonds and release small molecules sterilization,through the modification of chitosan,we choose another biomolecule dopamine to connect with borneol small molecules through the schiff base bond.Because active amino groups exist in dopamine,schiff base can also be formed with hydroxyl groups on borneol micromolecule BN,which is recorded as DPCN.The formation of schiff base is proved again by shedding and sterilizing borneol micromolecule in the composite material,and then the antibacterial performance of the composite material has been evaluated. |
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