Preparation Of PEGDA/CS Double Network Hydrogel And Its Application In Wound Repair Materials

Hydrogels are composed of an infinite three-dimensional network structure and water,which always lead to a soft performance.It is a wound dressing with good application prospects as they are similar to the natural extracellular matrix(ECM)and absorb exudates from wounds to maintain a moist environment,leading to the acceleration in wound repair.However,hydrogel-based wound dressings are generally prone to cracking when subjected to external loads due to poor mechanical properties.Especially,they cannot be stably fixed on the wound surface to avoid external microbial infection due to lack of insufficient adhesion ability and long-term antibacterial activity.Therefore,in view of the problems existing in current general hydrogel dressings,the covalent-ion dual crosslinked network of polyethylene glycol diacrylate(PEGDA)and chitosan(CS)or its derivative by two-step method of photopolymerization and salt solution soaking treatment were prepared.The mechanical properties,micromorphology,swelling,rheology,adhesion,in vivo degradation properties and biocompatibility of the prepared hydrogels were evaluated.The main research contents and experimental results are as follows:Firstly,the CS component was introduced to PEGDA polymer system,and PEGDA/CS DN hydrogel was prepared by UV photopolymerization and ion crosslinking.The introduction of CS effectively improves the mechanical properties of the system.And the maximum compressive fracture strength of the PEGDA/CS DN hydrogel was 0.58 MPa and the tensile strength was 96 kPa,which was significantly improved compared with the PEGDA hydrogel.The micromorphology and swelling ratio tests show that the PEGDA/CS DN hydrogel has a more uniform and dense porous structure than the PEGDA and its composite hydrogel,and exhibits a lower swelling ratio.The results of the rheological measures show that the system solution can be in situ rapidly formed a stable chemical cross-linked network structure under UV radiation,which can adapt to different shapes of wounds.The results of adhesion properties showed that the hydrogels exhibited better adhesion to different substrate surfaces.Cell experiments showed that the PEGDA/CS hydrogel has better cell affinity than PEGDA hydrogel,which reveals good biocompatibility of hydrogel system.Secondly,in order to further enhance the mechanical toughness of the hydrogel and the interaction with active substance,such as peptides and plasmids.In this study,CS was modified by thiolation to prepare thiolated chitosan(TCS),and the PEGDA/TCS hydrogel was prepared by two-step method.The mechanical evaluation results show that PEGDA/TCS DN hydrogel has better compression resistance and tensile toughness than PEGDA/CS system.The adhesion property was further improved and the adhesion strength to fresh pig skin was increased to 3.2 kPa.Hydrogels also have a suitable water vapor permeability,which can significantly reduce the evaporation of water as a wound dressing.Besides,the antibacterial peptide(PSI)with strong antibacterial activity was successfully loaded into the hydrogel system by the interaction of multiple cross-linking network structures and disulfide bonds,the loaded-PSI hydrogel can achieve sustained and stable release of peptide molecules and exhibit good antibacterial effect.The results of the cell test indicates that the PEGDA/TCS system have better bioadhesion,providing a better growth environment for cell adhesion and proliferation.The PSI-loaded hydrogel had no significant effect on cell viability while long-acting bacteriostatic,and the system still had good cytocompatibility.Finally,we constructed a full-thickness skin defect model of SD rats to evaluate the wound healing ability of hydrogel dressings.Morphology of skin wounds,postoperative healing rate,H&E staining of tissue sections,immunohistochemical staining of IL-1?,IL-6,and CD 31 were used to evaluate the effect of materials on full-thickness skin wound repair.The results showed that the loaded-PSI PEGDA/CS-PSI and the loaded-PSI-Angiopoietin plasmid(pANG)PEGDA/TCS-PSI-pANG hydrogel had good effects on promoting skin wound healing,but compared with PEGDA/CS-PSI system,PEGDA/TCS-PSI-pANG hydrogel exhibits optimal wound healing results due to the sustained release of PSI and pANG synergistically promoting rapid healing of wound tissue,which proved that the hydrogel system has a good application prospect in skin repair materials.