Preparation Of Polysaccharide Sponge Dressing And Its Properties Of Study In Hemostasis And Skin Wound Healing Promotion

In daily life and clinical operation,when severe skin trauma,uncontrolled bleeding is the first problem that needs to be addressed.In addition,when skin wounds are too deep and exposed to air for a long time,fluid loss and bacterial infection are likely to occur,which will significantly prolong wound healing time and even cause serious complications.Therefore,skin wound dressing should have the function of protecting the skin wound from bacterial infection after stopping bleeding.Natural polysaccharides are cheap and have a wide range of sources,and at the same time exhibit good biocompatibility,water retention,and degradability.The sponge dressing prepared with polysaccharide inherits the excellent air permeability and liquid absorption capacity of sponge and also has the advantages of polysaccharide.This study prepared polysaccharide sponge dressings with functions of hemostasis and skin wound healing promotion by simple modification and compounding.The specific contents are as follows:1.Chitosan(CS)is the unique alkaline polysaccharide in nature with abundant sources and active physical and chemical activities.For this,CS was selected as the main material,and the homogeneous solution was obtained by dissolving CS under acidic conditions in the second chapter.CS was crosslinked by graphene oxide(GO)under the action of chemical crosslinking agent(EDC/NHS)to enhance the stability and flexibility of chitosan sponge.At the same time,tannic acid(TA)was introduced to chitosan sponge to improve its the antibacterial ability and antioxidant properties.The freeze-dried CS/GO/TA sponge was treated with alkaline gas(NH3)to remove the acidity,which further increased its stability in solution.CS/GO/TA sponge showed good compression-recovery performance in aqueous solution,which was conducive to maintaining its porous structure at the wound surface.In addition,the abundant pore structure of CS/GO/TA sponge endows it the ability to absorb blood and body fluids,and the introduction of TA also enhances the ability of blood coagulation.The hemostatic and protective effect of CS/GO/TA sponge on skin wounds is conducive to wound repair,and can promote wound healing.2.Chitosan(CS)is easy to dissolve under acidic conditions,but the method to obtain stable CS sponges by removing acidity is too complicated,and the pore size of CS sponges obtained is not ideal.Therefore,CS-based cryogel dressing was prepared by physical crosslinking method in the third chapter.The local concentration of citric acid(CA)and CS increases under the condition of freeze-crystallization,which leads to the phase separation through electrostatic crosslinking,and then CS-based cryogel sponge was obtained after thawing.Chitosan-based cryogel sponge prepared by phase separation method endows it interconnected pore structure(pore size of 60-80 μm)and good stability.At the same time,silver nanoparticles(Ag NPs)were introduced into cryogel sponge through the reduction of Ag+with tannic acid(TA)as a reducing agent.The introduction of Ag NPs significantly enhances the antibacterial properties of CS/CA/Ag cryogel sponge and further improves the protective effect on skin wounds.Based on the high porosity of CS/CA/Ag cryogel sponge and the inherent hemostatic properties of chitosan,CS/CA/Ag cryogel sponge can absorb a large amount of blood and promote coagulation.CS/CA/Ag cryogel sponge have significant promoting effect on wound healing due to its good hemostasis and skin wound protection effect.3.In the second and third chapters,sponges prepared with chitosan(CS)have good hemostatic and wound protection,but the rapid hemostatic ability is insufficient.The large pore structure is conducive to blood absorption and rapid hemostasis.Therefore,Carboxymethyl cellulose(CMC)cryogel sponge with stable macroporous structure was prepared in the fourth chapter.Dopamine(DA)was grafted to CMC with chemical crosslinking agent(EDC/NHS)by chemical crosslinking method,which can easily control the amount of DA grafted.Under the condition of freeze-crystallization and oxidation of NaIO4,the DA on CMC and free DA in solution were oxidized and polymerized,and meanwhile the phase separation occurred.CMC/PDA cryogel with macroporous and interpenetrating structure was formed after thawing.The crosslinking degree of CMC can be controlled by changing the graft amount of DA on CMC,which achieve the control of the pore size of CMC/PDA cryogel sponge.The pore size of the cryogel sponge can reach 300-400μm,which can realize rapid hemostasis.In order to improve the antibacterial property of the cryogel sponge to promote the protection effect of skin wound,the synthesized silver nanoparticles(Ag NPs)were adsorbed on the CMC/PDA cryogel sponge to obtain the CMC/PDA/Ag cryogel sponge.The macroporous structure and antibacterial protection of CMC/PDA/Ag cryogel sponge are beneficial to achieve rapid hemostasis and promote skin wound healing.4.It’s difficult for conventional sponge dressings to reach the wound of irregular and deep skin wounds to achieve rapid hemostasis and provide wound protection.Therefore,the compressibility of sponges is required,and the structural recovery ability of sponges prepared in Chapter 2,3 and 4 after excessive compression is insufficient,which cannot meet the needs of injection.Based on this,bacterial cellulose(BC)with nanofiber structure was selected to prepare injectable BC-based cryogel sponge dressing.The natural three-dimensional network structure in BC endows it excellent hemostatic ability and recovery performance after compression.Using Oxidation polymerization,BC was oxidized by NaIO4 to form aldehyde-bacterial cellulose(DBC),which improves the biodegradability and chemical activity of BC.Under the condition of freeze-crystallization at low temperatures,DBC polymerized by aldol condensation and phase separation occurred simultaneously.DBC cryogels sponges were formed after thawing.However,the DBC cryogels sponges prepared by this method retained a lot of aldehyde groups,which cause certain cytotoxicity.In order to further enhance the biological safety and the antibacterial properties of DBC cryogel sponge,dopamine(DA)was introduced into DBC.DA was grafted onto DBC by reacting with the aldehyde group in DBC through the Schiff base reaction,and DA was oxidized and polymerized with free DA under oxidation effect of NaIO4.Meanwhile,phase separation occurred.DBC/PDA cryogel sponges were formed after thawing.The introduction of PDA enhances the photothermal properties of DBC cryogel sponges.DBC/PDA cryogel sponges can kill 90%of bacteria and provide wound protection under near-infrared light.Combined with its good injectable and rapid hemostatic ability,DBC/PDA cryogel sponges can also provide rapid hemostatic and protection in the face of irregular and deep skin wounds.In summary,a series of polysaccharide(chitosan and cellulose)sponge dressings were prepared by simple chemical crosslinking,physical crosslinking,and oxidative polymerization methods to meet different requirements for wound hemostasis and protection.The high porosity and hydrophilicity of polysaccharide sponges endow its good wound adhesion and hemostasis ability.The introduction of antibacterial and photothermal substance enhances the ability of polysaccharide sponges in inhibiting bacteria and preventing infection.Therefore,the prepared polysaccharide sponge dressing can promote skin wound healing through hemostasis and wound protection effect.