Study On In Vitro Antibacterial Effect And Safety Of Silver Ion Alginate Dressings

ObjectivesEstablish bacterial biofilm(BF)in vitro static models,determine the biofilm-forming ability of different bacteria,evaluate the in vitro antibacterial effect,subchronic toxicity and local response after implantation of silver ion alginate dressings,and provide a feasibility basis for using silver ion alginate dressings on the clinical treatment of chronically infected wound.Methods1.Construction of in vitro bacterial biofilm modelsmethicillin-susceptible Staphylococcus aureus(MSSA),methicillin-resistant Staphylococcus aureus(MRSA),Pseudomonas aeruginosa and Candida albicans were cultivated to the logarithmic growth phase and diluted to the same Concentration,cultured separately or mixedly in 96-well plates.24 hours later,the OD value of each bacteria culture was measured by crystal violet staining method to determine its biofilm-forming ability.2.In vitro antibacterial effect of silver ion alginate dressingsThe agar diffusion method was used to measure the inhibition zones and compare the antibacterial effects of silver ion alginate dressings and the corresponding antibacterial drugs.3.Subchronic toxicity of silver ion alginate dressingsTwenty-eight SD rats were randomly divided into a silver ion alginate dressings extract treatment group and a control group.The rats in the treatment group were injected with silver ion alginate dressings extracted with normal saline or sesame oil.The normal saline extract was administered by tail vein injection once a day at a dose of 10ml/kg;and the sesame oil extract was intraperitoneally injected on the first day,fourth day,seventh day,tenth day,and thirteenth day at a dose of 5ml/kg.The weight of each rat and the general appearance before and after injection,poisoning reaction and death were recorded every day.After 14 days,the rat was grossly dissected to observe and determine its clinical symptoms,organ coefficients,blood routine,blood biochemical,pathological and histological indicators.4.Local response after silver ion alginate dressings implantationFour SD rats were randomly divided into 2 groups for subcutaneous implantation tests on the back.T1 group:silver ion alginate dressings and reference substance-1(Biatain? Alginate Ag)with animal numbers T1-1 and T1-2.T2 group:silver ion alginate dressings and reference substance-2(Suprasorb A+Ag-LR)with animal numbers T2-1 and T2-2.The rats were sacrificed 4 weeks after implantation,and pathological sections were made on the skin of the implantation site.After staining with hematoxylin and eosin,the implantation site and surrounding tissues of the silver ion alginate dressings were observed and compared with the control.Results1.In vitro biofilm-forming ability of different bacteriaMSSA,MRS A,Pseudomonas aeruginosa,Candida albicans and their various mixtures all had strong biofilm-forming ability.2.Antibacterial effect of silver ion alginate dressingsThe corresponding antibacterial drugs against MRSA,Pseudomonas aeruginosa or Candida albicans all induced larger inhibition zones and hence better antibacterial effects than silver ion alginate dressings.Among the three bacterial strains,silver ion alginate dressings had the largest diameter of inhibition zone and thus the best antibacterial effect against Pseudomonas aeruginosa,followed by antibacterial effect against MRSA,and slightly less effective against Candida albicans.3.Subchronic toxicity of silver ion alginate dressingsNo animal died in the silver ion alginate dressings extract treatment group,and the general condition and main organs were normal;there were no significant difference in organ coefficients compared with the control group;in pathological examination,except for the lung,liver,kidney and ovaries had slight pathological abnormalities,the tissue structure,cell morphology and cell proportions of other organs were all normal;RBC,HGB,HCT,MHC and MCHC blood indicators had significant changes compared with the control group;blood biochemical indicators ALB,A/G,TG,ALT,AST,GLB,and BUN had also changed significantly compared with the control group.4.Local response after silver ion alginate dressings implantationThe 24 implantation sites of 4 rats were observed with naked eyes and found that the skin was slightly raised and there was no hemorrhage and scab on the surface.The skin was cut and there was a rice-sized nodule under the skin.Under the microscope,the skin was composed of stratum corneum,granular cell layer,spinous cell layer,basal cell layer,skin appendages,and subcutaneous tissue.The epidermis had mild keratosis.There was a buried plant in the connective tissue under the dermis,and the fibrous tissue around the plant had mild hyperplasia with mild hyperemia,edema and inflammatory cell infiltration.Among the 6 reference substance-1 implantation sites,there were 2 cases with obvious inflammatory cell infiltration and macrophages,and the number of blood vessels increased slightly.Among the 6 reference substance-2 implantation sites,3 cases had obvious inflammatory cell infiltration accompanied by the appearance of macrophages,vasodilation,congestion,and increase of blood vessels;2 cases had necrosis and cyst formation in the center of the implant;3 cases had mild inflammation,with necrosis and cyst formed in the center of the implant.In the 12 silver ion alginate dressings implantation sites,3 cases had slightly obvious inflammation,and 5 cases showed necrosis and cyst formation in the implanted center.Comprehensive scoring and statistical analysis of the inflammatory response of each sample showed that there was no significant difference in the inflammatory response of the reference substance-1 group,the reference substance-2 group and the silver ion alginate dressings sample group.Conclusions1.MSSA,MRSA,Pseudomonas aeruginosa,Candida albicans and their various mixtures all have strong biofilm-forming ability,which are suitable for constructing in vitro bacterial biofilm models for related research.2.The silver ion alginate dressings have a strong antibacterial effect against MRSA,Pseudomonas aeruginosa and Candida albicans,It is safe in Vivo and can be used as a reference for clinical safety.