Preparation And Antibacterial Properties Of Ion Crosslinked Sodium Alginate Double Network Hydrogel

Sodium alginate,as a kind of renewable polysaccharide which is rich in sources and widely exists in nature,is widely used in various fields of daily life and industrial production.In order to overcome the problems of insufficient mechanical properties,single function and difficult microstructure control of sodium alginate hydrogel,it is necessary to study sodium alginate and other polysaccharides to different fields.The composite of sodium alginate will be an important development direction.The composite of sodium alginate and other functional components（such as natural polymers,cations,etc.）can improve its performance and has important research and application value.In this study,sodium alginate was compounded with carboxymethyl chitosan and other biological polysaccharide materials,and ion crosslinking was used as the main cross-linking method to prepare natural polysaccharide-based interpenetrating or double-network hydrogels.Its antibacterial,mechanical and fluorescence properties were studied,and the microstructure of the hydrogel was regulated by cross-linking with different ions and changing preparation parameters and conditions.The specific results are as follows:（1）Based on the cross-linking of sodium alginate（SA）and carboxymethyl chitosan（CMC）with metal cations(Mⁿ⁺),a novel reversible multi-response metal-polymer fluorescent hydrogel was successfully prepared by template method.The double network formed by sodium alginate and carboxymethyl chitosan was used as a matrix for primary cross-linking with Ca²⁺(SA/CMC-Ca²⁺),and secondary ion crosslinking agents such as Cu²⁺and Zn²⁺were further added.Interpenetrating network hydrogels are formed by step-by-step cationic crosslinking.This synergistic ion crosslinking strategy improves the mechanical properties of SA/CMC gel films and produces shape memory behavior affected by p H.At the same time,it has adjustable fluorescence properties,stable antibacterial properties,qualitative analysis of bacterial detection and other properties,which can be used as multifunctional hydrogels for bacterial detection or antibacterial in the field of biomedical materials.（2）Using electrochemical workstation,using sodium alginate（SA）/carboxymethyl chitosan（CMC）as solution substrate and calcium disodium ethylenediamine tetraacetate（EDTA·Na₂Ca）as Ca²⁺source,SA/CMC-Ca²⁺/Cu²⁺hydrogel was prepared by electrodeposition（Electro-Deposited）.The hydrogel has complex spatial structure and enhanced mechanical strength,and the pattern of the hydrogel can accurately follow the design of the preset template.The height of the formed hydrogel can be controlled by the DC potential in the process of electrodepositing.compared with other technologies,the electrodeposition system has the advantages of low cost,high speed,high plasticity and high accuracy.at the same time,it also has many functions,such as ion cross-linking,model molecule embedding,self-healing and antibacterial properties.in addition,based on the characteristics of the two biopolymer-metal coordination driving interpenetrating networks.It also has the potential to extend the electrodes in this method to Cu,Zn,Ni,Ag,Fe and other metals.The double-layer structure and antibacterial properties of the gel will be used in biomedicine,especially in the field of tissue engineering and wound dressing.（3）the double-network hydrogel fibers with double stimulation response were prepared by extruding the hot mixture of sodium alginate（SA）and agarose（Agar）into the precooled coagulation bath containing metal cations.Higher spinning speed will lead to new micro-gully patterns on the fiber surface,and further extreme freezing process will lead to complex wrinkle patterns on the fiber surface.Metal cations such as Ca²⁺and Zn²⁺can be introduced into the gel matrix as ion crosslinking agents to obtain double-network hydrogels with enhanced mechanical properties,antibacterial properties and fluorescence properties.In addition,SA-Mⁿ⁺and Agar networks are functionally dependent,such as the typical p H sensitive shape memory performance.The stimulus-responsive hydrogel microfiber can be used in biomedical system as a material for immobilization and control of antimicrobial agent release.To sum up,the natural polysaccharide hydrogel with interpenetrating or double network structure with controllable microstructure in this study,because of its simple preparation method,enhanced mechanical properties,good antibacterial properties and a variety of functions（such as fluorescence,shape memory,etc.）,it will provide an important supplement for the construction methods of biological polysaccharide macromolecule hydrogels,and has great application potential in the field of biomedical hydrogels.