Study On Catechol Chitosan/Polyacrylamide Double Network Hydrogel Loaded With RvE1

The recovery of difficult-to-heal wounds and the accompanying inflammation are extremely difficult problems in clinical treatment.Difficult-to-heal wounds are usually accompanied by continuously chronic inflammation,localized low pH and high oxidative stress condition,which limited cell growth and proliferation.Ordinary medical gauze has limited therapeutic effects on difficult-to-heal wounds.The research and development of multifunctional wound dressings had become an important direction to replace clinical medical gauze in the treatment of difficult-to-heal wounds.In this regard,this paper used polyacrylamide to prepare double network hydrogels based on chitosan hydrogels,which can enhance the mechanical properties of natural macromolecular hydrogels while ensuring good biocompatibility.Catechol group and the used of nanoparticles to load the hydrophobic drug inflammation regulator RvE1,could promote the healing of the wound by promoting cell adhesion and regulating the inflammatory at the wound site.Using crosslinking agents containing disulfide bonds to prepare redox responsive double network hydrogels and prepared pH-responsive nanoparticles that can target low pH and high oxidative stress of chronic inflammatory microenvironment,which formed an intelligently release drug delivery system for drug release.Firstly,the chitosan was modified with catechol groups（C-CS）,the modification and the grafting rates of the catechol groups were detected by UV and ¹H-NMR.To form a redox-responsive hydrogel with cystamine,and the gel had the best stability,which explored and screened the best gel forming process:used a modified chitosan with the grafting rate of12.3%,dissolved in ice bath,and gelled at 37°C.The structure of the hydrogel became loose after adding H₂O₂,which proved that the hydrogel had redox response capability.The catechol-modified chitosan hydrogel was characterized by FT-IR,XPS,and SEM.The results showed that cystamine cross-linked the catechol-modified chitosan through Michael addition or Schiff base reaction to form a hydrogel,which pore size was about 100-200μm.Next,acrylamide（AM）was used as the monomer of the second network of the double network hydrogel,and N,N’-methylene bisacrylamide and N,N’-bis（acryl）cystamine were used as crosslinking agent,initiated free radical polymerization by photoinitiator to prepare double network hydrogel（C-CS/AM）,testing the swelling performance,tensile and compressive properties of the hydrogel,it was found that the swelling performance and mechanical properties of the double network hydrogel were significantly increased.The XPS characterization results indicated that the disulfide bonds of the double network hydrogels containing disulfide bonds in the two hydrogel networks were the most stable and had the ability to release drugs responsively.The pore size of the double network hydrogels was reduced to 10-20μm under SEM observation.The endothelial cells were used to detect the enhancement of cell adhesion ability of hydrogels containing catechol groups.The experimental results proved that the catechol groups in the hydrogel had the effect on enhancing the adhesion ability of cells.Then,β-cyclodextrin was modified by acetalization,and detected by FT-IR and¹H-NMR.Under ultrasonic conditions,the acetalized modifiedβ-cyclodextrin self-assembled in water to form nanoparticles.TEM detected the particle size distribution was 70 nm and 300 nm.And the DLS found that the hydrated particle size of the nanoparticles was 609.1 nm,which increased to 652.2 nm after loading RvE1.In pH=5.4,the hydrated particle size increased to 681.4 nm and 891.1 nm,respectively,which proved that RvE1 were successfully loaded and nanoparticles had pH responsiveness.The cytotoxicity of the nanoparticles was evaluated using L929 cells.The experimental results found that the high concentration of nanoparticles in a short time has a little inhibitory effect on cell proliferation,but it had no effect on cell proliferation at low concentration and at long-term.Finally,the nanoparticles loaded with the inflammatory regulatory factor RvE1 were loaded into the double network hydrogel to prepare a dual-responsive hydrogel drug carrying system.SEM-EDS detection showed that the nanoparticles were successfully loaded into the double network hydrogel.Activity and proliferation experiment of macrophages,endothelial cells,and L929 cells were used to evaluate the biocompatibility of the double network hydrogel.The results showed that endothelial cells hardly proliferated on the surface of the hydrogel.Macrophages and L929 cells proliferated slowly at 1 day,but there were obviously proliferation between 3-5 days.Moreover,at 5 days,a certain concentration of RvE1 can promote the release of interleukin-10 from macrophages,which had showed anti-inflammatory effect.A wound was made on the back of SD rats,and the double network hydrogel was used as a wound dressing to test its effect on wound healing.The results of HE and Masson staining showed that the double network hydrogel can promote wound repair.The promotion effect of repair was more obvious after RvE1 loaded.The preparation of the double network hydrogel in this study can be used to personlly treat and regulate the inflammatory microenvironment of difficult-to-heal wounds.It also provides new ideas for solving the lack of mechanical properties of natural macromolecular hydrogels and the design of hydrogel drug-carrying systems.