| Skin,as the most important barrier of human beings and animals,is often damaged.When animal skin is injured,the body needs to mobilize precise and complicated repair procedures to make the wound heal again.In veterinary clinic,animal trauma is often accompanied by infection,which will aggravate inflammatory reaction and seriously affect wound healing.Treatment drugs for infected wounds need to be able to accelerate the healing process while solving the problem of anti-bacteria and anti-inflammation.The research on antibacterial and healing promoting drugs has always been a hot topic.At present,antibiotics are mainly used for the treatment of infectious wounds,but with the long-term use of antibiotics,the problem of bacterial drug resistance is becoming more and more serious.Silver,especially nano silver,can interact with bacteria,destroy its stability and affect the synthesis of genetic materials,thus having strong antibacterial effect.However,due to the instability of nano silver,the preparation and storage of nano silver often require the introduction of stabilizers and carriers,which leads to a very complex preparation method of nano silver.Chitosan,as a drug carrier,has the advantages of histocompatibility,non-toxicity and degradability,hemostasis,analgesia,wound healing promotion,antibacterial,etc.Current research shows that the combined application of chitosan and nano silver can enhance the antibacterial effect and effectively promote wound healing.However,chitosan itself has the defects of poor water solubility and low mechanical strength.This will make the compound have tissue irritation when acting on the wound on the animal’s body surface,or cannot effectively play its function.Therefore,we have deeply studied a new type of chitosan nano silver complex which can effectively treat animal infection.The composite has the remarkable advantages of not stimulating the animal body surface,simple preparation method,high efficiency of antibiosis and antiphlogosis,rapid promotion of wound healing and the like,and solves the defects of the traditional nano silver composite material.Catechol chitosan（CCTS）with different grafting ratios were synthesized by chemical modification.Various catechol-chitosan nano silver（CCTS/Ag）sols were obtained by direct reaction of CCTS with AgNO3 solution and changing reaction conditions.The appearance of CCTS/Ag sol was observed and the physical and chemical properties of nano silver and sol were qualitatively characterized.It was found that the best preparation method of CCTS/Ag sol was to use CCTS with graft ratio of 9.93%and 2 mg/mL AgNO3 solution to react under certain conditions for 30 min and then to stand.TEM showed that the particle size of nano silver in CCTS/Ag sol was about 20 nm,and the concentration of stock solution was 60.56 μg/mL by ICP-OES analysis.To test the actual bacteriostatic and healing properties of the CCTS/Ag sol,an in vitro bacteriostatic test and an animal model treatment test of infection wound were carried out in this test.The minimum inhibitory（bactericidal）concentration,inhibition（killing）rate and bacteriostatic time were recorded in vitro bacteriostatic test.In animal experiments,the average granulation tissue formation time,average wound complete healing time,wound area healing rate and wound volume healing rate of infected wounds were calculated,and HE staining and Masson staining tissue sections of rabbit skin wounds were made.The bacteriostatic test results showed that the MIC of CCTS/Ag sol on Pseudomonas aeruginosa was 30.28 μg/mL,the bacteriostatic rate was 91.9%,the MBC was 48.44μg/mL,the bactericidal rate was 100.0%,and the bacteriostatic time was greater than 96 h under the drug MIC.The MIC of Staphylococcus aureus was 12.11 μg/mL,the bacteriostatic rate was 99.6%,the MBC was 24.22 μg/mL,the bactericidal rate was 100.0%,and the bacteriostatic time was up to 24 h under the drug MIC.CCTS/Ag sol had long-term bacteriostatic ability to Pseudomonas aeruginosa and Staphylococcus aureus.The results of animal tests showed that CCTS/Ag sol had no skin redness around the wound,pain stimulus,allergy and other reactions during medication.The healing rate of wound area（89.37%）and wound volume（97.50%）in CCTS/Ag sol group were always higher than those in negative control group.In CCTS/Ag sol group,granulation formation was first found on 4.17 d and healed completely at the earliest on 11.33 d.Observation of tissue sections showed that inflammatory cell infiltration in CCTS/Ag sol group was the least,capillary proliferation was obvious,and collagen fiber centripetal growth,epithelial tissue proliferation and wound remodeling were observed first.The above test results show that CCTS/Ag sol has no obvious irritation and can effectively inhibit bacteria and inflammation,and can promote granulation formation and wound contraction efficiently,and thus accelerate the healing process. |
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