Preparation Of CpG ODNs-loaded Hydrogel For Wound Repair

The skin plays a vital role in protecting the body from external stimuli,but it is also susceptible to environmental factors due to exposure.Injuries disrupt the function of the skin and eventually form wounds.It is common practice to use medical dressings on the wound to speed up its healing.At present,most of the dry non-woven dressings used in clinical practice are dry non-woven dressings,although they are low cost and widely sourced,they are also easy to adhere to the wound due to the absorption of wound exudate,and it is easy to cause damage to the new skin tissue when changing the dressing.Since George Winter proposed the concept of wet healing in the seventies of the last century,the theory of wet healing of wounds has been accepted and paid more and more attention,and now many wet wound dressings have been developed,such as alginate,hydrocolloid and hydrogel.Among them,hydrogels have attracted widespread attention because of their high water content,good biocompatibility and threedimensional porous structure of extracellular matrix.However,ordinary hydrogel dressings can only play the role of physical isolation and creating a humid environment,and cannot meet the clinical requirements for wound dressings.Therefore,there is an urgent need to develop multifunctional hydrogel wound dressings to meet the various needs of wound repair.Synthetic non-methylated cytosine-guanosine oligodeoxynucleotides(CpG ODNs)are a class of substances with immunostimulating activity,which can activate the human immune system,promote fibroblast proliferation and migration,and then promote wound healing.In this paper,a multifunctional hydrogel wound dressing loaded with CpG ODNs was constructed based on CpG ODNs and collagen and chitosan with good biocompatibility.This hydrogel dressing can slowly and continuously release CpG ODNs,promote fibroblast proliferation and migration,and accelerate wound healing.First,collagen(Collagen,Col)is obtained from the cattle Achilles tendon through pretreatment,degreasing,enzymatic hydrolysis and salting.Infrared spectroscopy,scanning electron microscopy and SDS-PAGE analysis proved that the extracted collagen had the characteristics of type I collagen.The extracted collagen and chitosan were mixed in volume,different concentrations of CpG ODNs were added to mix,and then the crosslinking agent dopamine and ammonium persulfate were added to the mixed solution,and the Schiff base reaction occurred to prepare CCSDC hydrogels loaded with CpG ODNs..Swelling experiments show that the hydrogel has excellent rapid swelling performance,and the swelling rate can reach up to 918% in 2 hours.In addition,the results of alternating strain scanning experiments and lap shear experiments show that CCSDC hydrogels also have excellent self-healing properties and tissue adhesion properties.The results of in vitro drug release experiments showed that CCSDC hydrogels could release CpG ODNs slowly.The above results show that a multifunctional hydrogel with sustainable release of CpG ODNs with good swelling performance,self-healing performance and tissue adhesion performance has been successfully prepared.The biocompatibility of CCSDC hydrogel was evaluated by hemolysis experiment and cytotoxicity experiment,and the hemolysis rate of CCSDC hydrogel was less than or equal to5%,and it had no obvious cytotoxicity to NIH-3T3 mouse embryonic fibroblasts,indicating that CCSDC hydrogel had good biocompatibility.The results of scratch experiments showed that CCSDC hydrogel could promote the migration of NIH-3T3 mouse embryonic fibroblasts.A mouse acute wound model was constructed to evaluate the effect of CCSDC hydrogel on wound healing.The results of wound contraction showed that CCSDC hydrogel could promote acute wound healing,and the cytokine determination results in vivo showed that CCSDC hydrogel may induce immune response and accelerate wound healing.The results of histological analysis showed that CCSDC hydrogel could promote the production of blood vessels and fibroblasts and collagen deposition,and did not cause damage to the heart,liver,spleen,lungs and kidneys of mice.The above results show that CCSDC hydrogel is expected to be used as a multifunctional wound dressing in the field of wound repair.