| Biofilm retains the spatial structure of dermal tissue that is conducive to skin regeneration,and is a skin substitute that has been put on the market.In actual use,the mechanical properties of biofilm change with degradation,and it is often torn at the suture.At present,there is no relevant research to analyze the mechanical properties and tearing force of biofilm after degradation,which brings difficulties to clinical application of biofilm.Besides,biofilm has no antibacterial ability,so wound infection cannot be avoided.In order to provide data support for clinical use of biofilms,reduce the probability of breakage and damage of biofilms in use,and increase the anti-infection ability of biofilms,the mechanical properties of degraded biofilms were first studied,and the tearing force of biofilms was tested by classification.Then,gentamicin sulfate was loaded on biofilms by post-drug loading method,so that the biofilms could be antibacterial and functional.Finally,whether the mechanical properties and physical and chemical properties of drug-loaded biofilms could meet the clinical requirements was studied.Through analysis,the following conclusions are finally obtained:(1)The biofilm was degraded for 2-36 days,the tensile strength was always between 8.50-29.62 Mpa,and the elongation obviously increased with the degradation time.The mechanical properties of degraded biofilm are still better than those of human leg skin.The measurement shows that the thickness of biofilm is 0.3-0.9mm.Because the thickness span is too large,biofilms are divided into six groups according to their thickness,namely,0.3-0.4mm group,0.4-0.5mm group,0.5-0.6mm group,0.6-0.7mm group,0.7-0.8mm group and 0.8-0.9mm group.The tearing forces of six groups of dry and wet biofilms were tested with 2-0,3-0 and 4-0 sutures at the margins of 2mm,3mm,4mm and 5mm respectively.It was found that the tearing forces of dry biofilms stitched with 2-0,3-0 and 4-0 sutures were 14.29-42.61 N,11.25-28.54 N and 12.75 respectively.Generally speaking,the tearing force of biofilm increases with the increase of film thickness and suture margin,and the tearing force of the film sewn with thicker suture and dry biofilm may be greater.After comprehensive mechanical analysis,it is found that the stress of the biofilm should be less than 8.50 N in order to avoid the damage of the biofilm after suturing the wound.(2)Macroscopic and SEM analysis proved that the biofilm is stable in deionized water,so the biofilm can be functionalized by post-drug loading.At 37℃,the biofilm was immersed in 50mg/ml gentamicin sulfate solution for 24 hours,and then freeze-dried to obtain the drug-loaded membrane.(3)Through appearance analysis,depth of field and SEM,it was observed that there were drugs on the rough surface,glossy surface and side of the drug-loaded film.The XRD curve of the drug-loaded film lies between the biofilm and the gentamicin sulfate curve.The diffraction peaks of drug-loaded film appear at 8 and 20,and the positions of the peaks are the same as those of biofilm and gentamicin sulfate.After comprehensive analysis,it was found that gentamicin sulfate was successfully loaded on biofilm and had no effect on collagen.The tensile strength of the drug-loaded membrane is 5.53-29.25 Mpa,which is higher than that of human leg skin.The thickness of drug-loaded membrane is thicker than that of biofilm,ranging from 0.4-1.0mm to 1.0 mm.According to the thickness,the drug-loaded membrane was divided into the following six groups: 0.4-0.5mm group,0.5-0.6mm group,0.6-0.7mm group,0.7-0.8mm group,0.8-0.9mm group and0.9-1.0mm group.Six groups of drug-loaded films were stitched with 2-0,3-0 and 4-0stitches at the margins of 2mm,3mm,4mm and 5mm,respectively.The tear forces of drug-loaded films stitched with 2-0,3-0 and 4-0 stitches were measured to be6.99-36.81 N,8.82-28.50 N and 9.09-18.13 N,respectively.Generally speaking,the tearing force of drug-loaded film increases with the increase of thickness and suture margin.Under the same thickness and margin,the tearing force of drug-loaded membrane is smaller than that of biofilm.After comprehensive analysis of the mechanical properties of the drug-loaded membrane,it was found that the force of the drug-loaded membrane should be less than5.53 N after suturing at the wound site.The drug loading rate of drug-loaded membrane is 14.18%,which is hydrophilic and conducive to cell adhesion.The thermal denaturation and thermal decomposition temperature of the drug-loaded membrane are 121 ℃ and 200-500 ℃ respectively,which has sufficient thermal stability and will not be denatured and thermally decomposed when applied clinically.The PH values of leaching solution of drug-loaded film at 12 h and 24 h are 5.41 and 5.55,respectively,which are within the normal skin PH range.Therefore,the drug-loaded film sutured on the skin surface will not cause a significant change in wound PH and affect the wound closing speed.The water absorption rate of the drug-loaded membrane is 371.08%,which meets the clinical requirements,and can absorb exudate while keeping a moist wound environment.After18 hours and 24 hours of degradation,the degradation rates of the drug-loaded membrane were over half and over 90% respectively.Generally speaking,the mechanical properties and physical and chemical properties of drug-loaded membrane can meet the clinical requirements,and it is a potential antibacterial skin substitute. |
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