| OBJECTIVE:Chronic wounds caused by bacterial infections have become a major medical threat and challenge,and there is an urgent need to develop wound dressings with good antibacterial properties.The key to further improvement and optimization of antibacterial dressings is to select antibacterial agents with better antibacterial effects and to improve the antibacterial adhesion ability of the dressing.Cellulose used in wound dressings shows good cell compatibility and tissue compatibility,and provides a continuous humid environment,which is conducive to skin regeneration.However,it does not have antibacterial activity and cannot prevent wound infections.It has high permeability and poor hydrophobicity.Bacteria tend to adhere to its surface to form a biofilm that is difficult to remove,and it tends to stick to the sore especially upon drying.The design and improvement of cellulosic materials from the aspects of improving antibacterial activity and hydrophobicity are necessary conditions for obtaining ideal wound dressings.Under this premise,this subject designs the modification of cellulose by perfluoride and guanidine salt,and mixes the modified product to prepare a film,and explores its role as a wound dressing to promote the healing of infected wounds.Method:This research is divided into three parts.Part Ⅰ:Modification of cellulose and preparation of cellulose film.(1)Modification of cellulose.The cellulose raw material(C)was grafted with trifluoroacetone,heptafluorobutyraldehyde and aminoguanidine hydrochloride to obtain trifluoroacetone modified cellulose(F3C),sevofluorobutyraldehyde modified cellulose(F7C)and aminoguanidine hydrochloride modified cellulose(GC).(2)Characterization of modified cellulose.The modification effect was verified by FTIR and XPS,the effect of modification on the thermal stability of cellulose was characterized by TG/DTG detection,and the effect of modification on the bulk structure of cellulose was analyzed by XRD.(3)Preparation of cellulose film.C,F3C,F7C and GC are mixed in pairs,and cellulose membranes is made with a vacuum filtration device.(4)Characterization of cellulose film.The mechanical properties,microscopic morphology and hydrophobicity of the membrane were characterized by tensile performance test,SEM and hydrophobicity experiment.This part lays the foundation for subsequent in vivo and in vitro experiments.Part Ⅱ:In vitro experiment of cellulose membrane.(1)Biocompatibility test of cellulose membrane.CCK-8 and Calcein-AM/PI staining were used to detect the biocompatibility of cellulose membranes.(2)Characterization of antibacterial properties of cellulose membranes.The antibacterial activity of each group of membranes was verified by in vitro antibacterial experiments.Part Ⅲ:In vivo experiment of cellulose membrane.(1)Construction of animal models.Create a skin defect on the back of SD rats and apply bacterial liquid to make animal models of infected wounds.(2)Evaluation of wound healing.Evaluation of skin wound healing by gross observation.(3)Observation of tissue sections.Samples were taken 14 days after modeling,and H&E and Masson staining were performed to verify the role of each group of membranes in promoting healing of infected wounds.Results:FTIR and XPS results showed that fluorine from perfluoride and nitrogen from aminoguanidine hydrochloride were grafted onto cellulose,respectively.Compared with the raw material,the TG/DTG data of perfluoride modified cellulose has an increase in the weight loss rate,and the TG/DTG data of the guanidine modified cellulose has a lower initial thermal decomposition temperature than the raw material.There is no significant difference in the XRD patterns of cellulose before and after modification.Tensile performance test showed that the Young’s modulus of each group of modified cellulose films has a certain increase compared with pure cellulose film.The SEM of each group of cellulose membrane has no obvious difference,the fiber shape is uniform,the surface is smooth and there are high-density pores,showing a typical three-dimensional network structure.In the general observation of the hydrophobicity experiment,the perfluoride-containing cellulose membrane has a certain degree of hydrophobicity,and the hydrophobicity of the membrane containing F7C is better than that of the membrane containing F3C.The results of CCK-8 and Calcein-AM/PI staining showed that the cellulose membrane of each group had no effect on the proliferation of fibroblasts.The cellulose membrane containing GC formed an obvious inhibition zone in the in vitro antibacterial experiment.In animal experiments,the infected wounds covered with the cellulose membrane mixed with F7C+GC healed almost completely.In contrast,the wounds treated with normal saline and pure cellulose membranes healed poorly.The HE staining of the tissue sections showed that the skin wound tissue treated with the modified cellulose membrane regenerated better,with skin appendages such as hair follicles,which was close to normal skin tissue.In contrast,the control group and the pure cellulose group did not show complete regeneration of the epidermis and dermal tissue,and the epidermis became thicker.Masson staining observed increased collagen deposition in the wound area of each group,but the collagen deposition in the skin wound treated with the modified cellulose membrane was denser and more organized.Conclusion:In this experiment,the cellulose was successfully modified.The modification caused a certain degree of change in the thermal stability and mechanical properties of the cellulose raw material,but did not affect the bulk structure of the cellulose and the microscopic morphology of the cellulose membrane.Cellulose has been modified to have a certain degree of hydrophobicity and antibacterial activity.Each group of cellulose membranes have good biocompatibility,and the modified cellulose membranes can obviously promote the healing of infected wounds,and have good application potential as antibacterial wound dressings. |
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