Preparation And Biological Activity Of Bismuth Sulfide (Tellurium Dioxide)/Antibiotic/Chitosan Dressings

Skin is the outermost barrier of the human body.Once damage,skin is easy to be infected by the invasion of external bacteria.However,the vast and nonstandard use of antibiotics in clinical practice has greatly increased the number of drug-resistant bacteria,and many traditional antibiotics have lost their efficacy against drug-resistant bacteria.Traditional dressings are not effective in promoting wound healing and fighting against drug-resistant bacteria,as a result the development of new wound dressings becomes a hot research topic.Chitosan has good biological compatibility,antigen-free,non-toxic,hemostatic,water absorption and moisture retention,but its antibacterial properties do not meet the requirements of fighting wound infection.In previous work,our team found that Bi2S3 nanomaterials have synergistic effects with GEN against MRSA.So does on TeO2 and CTX.And Bi2S3 has a good photothermal response,which can effectively enhance the antibacterial activities of the materials.Based on this,Bi2S3/GEN/CS dressings and TeO2/CTX/CS dressings were prepared in this study.The dressings were characterized,the physical properties and the antibacterial properties against MRSA were determined.And the toxicity to normal mouse cells,the healing effect on the mice wound infected by the resistant bacteria of the dressings were further studied.The main research contents and results are as follows:(1)Bi2S3/GEN/CS composite dressing was prepared by in-situ synthesis and immersion method.The successful synthesis and microstructure of Bi2S3 in dressing were determined by X-ray diffraction(XRD)and scanning electron microscopy(SEM).The porosity,absorbent and water retention properties of the dressing were tested.And we verified the antibacterial activity,mechanism and toxicity of the dressing to normal mouse cells(L929)under NIR.The experimental results showed that the composite dressing was a porous sponge structure with porosity of over 47%.And the water absorption rate is more than 900%and it can retain water over 20 h.Under 10 min of NIR illumination,the inhibition rate of the dressing(1 cm on each side)containing 0.2 g GEN against MRSA was 99.4%.The heat generated by NIR composite dressing,the release of Bi2S3 and GEN from the dressing,and the destruction of cell structure were all the causes of bacterial death.The compound dressing had no obvious toxicity to the cells.And the dressing can promote blood coagulation in vitro.(2)The healing effect of Bi2S3/GEN/CS dressing under NIR on MRSA infected wounds in mice was tested.The experimental results showed that Under NIR,the composite dressing had a good photothermal effect,and the surface temperature of the dressing was increased to 16.8?.Combined with the synergistic effect of Bi2S3 and GEN,it can effectively reduce the number of bacteria in the wound bed.By promoting the proliferation of wound granulation tissue,the formation of scar tissue was reduced,and the wound healing time was shortened.On the third day,the wound area could be decreased 47.01%.(3)TeO2/CTX/CS dressing was synthesized by in-situ synthesis and immersion method.We can observed porous sponge structure by SEM,and the pore size is 50-100?m.The porosity of the dressing is 63%and it can retain water over 20 h.Different from Bi2S3/GEN/CS dressing,the TeO2/CTX/CS dressing has no photothermal effect,but the survival rate of MRS A after processing by a dressing(1 cm on each side)containing 0.2 g CTX is 3.66%.At the same time,the cell survival rate was still over 90%.The dressing can also promote blood coagulation in vitro.