Effect Of Preparation Processes On The Structure And Properties Of Antibacterial Braided Silk Suture

Braided silk surgical suture has been widely used in various surgeries for its goodpliability and handling properties. However, the braided structure of silk suture canallow the easy adhesion of bacteria to the materials, thus resulting in high rates ofsurgical site infections. The development of suture with long-lasting antibacterialproperties can prevent SSIs effectively. Nevertheless, the current researches onantibacterial silk suture mainly focus on antibacterial finishing of suture, and seldomsystematically analyze the effect of coating, braiding and finishing processes on itsstructure and performance. Coating of silk multifilament yarns was applied. There’ssome guiding significance for the industrial production of antibacterial silk suture byresearch and optimization of its preparation process.Silk multifilament yarns were coated by a combination of polycaprolactone (PCL),levofloxacin hydrochloride and acetic acid. PCL is a biodegradable polymer used asbiomedical materials approved by the Food and Drug Administration. Levofloxacinhydrochloride is an antibacterial drug with broad-spectrum antibacterial property.Antibacterial braided silk sutures were prepared by braiding process. The coatingprocess, braiding process and heat setting process were discussed in this paper.Optical microscope and scanning electron microscopy were used to observe andanalyze the suture morphology and structure. The zone of inhibition againstEscherichia Coli (E. coli) and Staphylococcus Aureus (S. aureus) was evaluated bythe agar diffusion method. Mechanical properties, such as knot mechanicalproperties, bending stiffness and friction were tested to analyze the influence ofdifferent parameters on antibacterial silk sutures.The coating parameters included coating repetitions, molecular weight of PCL,concentration of PCL and concentration of antimicrobial drug. The results showedthat suture of2coating repetitions exhibited better antibacterial effect, knotting strength and friction performance. The antibacterial efficacy against E. coli and S.aureus improved with the increase of molecular weight or concentration of PCL, andalso the concentration of antimicrobial drug.Different antimicrobial silk sutures were prepared by adjusting the braiding gearratio. The diameter, braiding density and braiding angle were measured respectivelyby electronic thickness gauge and optical microscope. The results showed that, withthe increase of gear ratio, the suture became more compact and the braiding densityincreased. The braiding density had significant effect on the structure andmechanical properties of suture (P<0.05). Braiding density had no significant effecton the zone of inhibition (P>0.05).In addition, orthogonal experiment method was applied to investigate the influenceof heat-setting temperature, heat-setting time, and their interaction on theperformance of suture. The results showed that the antimicrobial braided silk suturewas cleaner after heat setting. The process had some positive effect on theantibacterial properties (P<0.05). It showed the greatest impact on the bendingstiffness. After heat setting, the knot strength and bending stiffness of suture wereincreased. In conclusion, the optimal heat setting parameters were heat-settingtemperature of120℃and heat-setting time of3min.In summary, the coating process of antibacterial silk suture had great influence onthe antibacterial property, and the braiding and heat setting process had some effecton the structure and mechanical properties. By optimization of process parameters,sutures with good antibacterial property, mechanical properties up to the usingstandard and potentiality to industrial production were prepared.