Preparation And Properties Of Chitin-based Antibacterial And Hemostatic Sponge

Uncontrollable hemorrhaging is a major cause for mortality from traumatic injuries,which frequently happens in battlefields and civilian accidents.At the same time,bacterial infections are another extremely challenging problem in post-traumatic treatment.Until now,a series of hemostatic,e.g.Quik Clot^?,Celox^?,Hem Con^?,Surgicel^?etc.exhibit excellent hemostatic properties,but these traditional materials are only suitable for traumas and can hardly treat deep,narrow and irregular wounds.Chitin,the second most abundant naturally occurring polysaccharide,has outstanding properties in biocompatibility,biodegradability and can promote wound healing.In this thesis,chitin is used to construct a series of advanced hemostatic materials with dual functions of rapid hemostasis and antibacterial,and they are applied to surface wounds and puncture wounds.The relationship between its structure and hemostatic and antibacterial properties is explored,and the hemostatic mechanism is elucidated.The specific content is as follows:（1）The chitin sponge（CTS）with a porous structure was obtained by the sol-gel method.Using the strong adsorption capacity of chitin for metal ions,a chitin/ZIF-8composite sponge（ZIF-8-CTS）was fabricated by in situ growth of ZIF-8 nanoparticles into CTS.ZIF-8 nanoparticles were uniformly distributed on the surface and inside of the chitin sponge,forming a hierarchical porous structure with a specific surface area of～126.2 m²·g^-1.ZIF-8-CTS was super-hydrophilicity,and could accelerate blood absorption to concentrate red blood cells and platelets to form a primary blood clot.Meanwhile,upon contact with blood,ZIF-8 nanocrystals could gradually release Zn²⁺to activate the blood coagulation cascade reactions.Benefiting from these two synergistic effects,ZIF-8-CTS exhibited superior hemostasis performance than the traditional hemostatic materials（cotton gauze and gelatin sponge）in the rat femoral artery and liver injury models.Furthermore,it displayed excellent cytocompatibility and hemocompatibility.Importantly,it had an outstanding bactericidal effect with antibacterial ratio of up to 100%for Gram-negative Escherichia coli and Gram-positive Staphylococcus aureus.These results demonstrated that ZIF-8-CTS is an excellent antibacterial hemostatic material,and has high potential in the application of hemostasis for clinical surface wounds.（2）Quaternized chitin（QC）was obtained by introducing quaternary ammonium salt into the molecular chain of chitin;And then,the chitin was split into chitin nanofibers（CN）by mechanical peeling method.Finally,QCNS which QC and NC was its skeleton was fabricated by the freeze-drying method.QCNS presented an interpenetrating microporous structure,and its water absorption rate could reach up to 13044±275%.It’s volume could be reduced,when the absorbing water of sponge was squeezed.When the compressed QCNS was soaked in blood,it could quickly restore its shape by absorbing blood less than1 s,which was conducive to its formation by syringe injection into the depth of the wound.At same time,the surface of QCNS contained rich quaternary ammonium salts and amino groups,which could make it to absorb and enrich red blood cells and platelets in the blood through electrostatic interactions to promoted blood coagulation.When applied in the cylindrical wound on rat liver as noncompressible wound models,QCNS displayed superior hemostatic performance than traditional hemostatic materials such as medical gauze,gelatin sponge and Celox^?.More importantly,QCNS displayed excellent antibacterial activity,cytocompatibility,and hemocompatibility,and has highly potential in the clinical application of hemostasis for puncture wounds.