A study of the impact of ethylene oxide sterilizing modes on properties of glycolactic sutures

Gas sterilization by ethylene oxide is widely used because of antibacterial, sporicidal, virucidal ethylene oxide properties. Gas sterilization method is an economic and low temperature method. It is used for surgical suture sterilization including surgical suture materials made of glycolic and lactic acid copolymers (polyglycolide lactide). Ethylene oxide sterilization procedure is to be conducted at a certain level of humidity that sometimes can reach 80%. During sterilization water vapor and gas mixture can impact the temperature of vitrifying and the molecular mass of a biopolymer. This can change the physical and mechanical properties of polyglycolactic suture. This impact must be taken into consideration when conducting ethylene oxide sterilization. Researches on the impacts are presented in this article. Laboratory-scale polyglycolide lactid sutures are obtained by one-step polymerization and extrusion process in a specially designed extruding press on the base of HAAKE Process 11 from glycolide and dl-lactide (glycolide/lactide 95/5 mole %) with addition of 500 ppm tin octoate (II). The metric size of the suture was four after orientation stretching. The sterilization procedure is conducted in gas sterilizer/oxygenator Steri-Vac, 5XLPB Model, 3M Company production (USA). Residual strength (by load rate at the basic knot rupture) is determined after storing in model internal environment - phosphate buffered solution, рН 7.4, at the temperature of 37°C - to find out the impact of humidity and sterilization temperature on suture degradation period. A complex of research methods such as DSC-analysis, titrating, knot breakage testing in a tester are used to characterize the parameters. During the research of sterilization modes of polyglycolide-lactide sutures of metric size four it was found that the optimal sterilization mode is conducted at ethylene oxide concentration of 750 mg/l, humidity of 70% and temperature of 37°C. After the sterilization procedure it is required to perform aeration during eight hours at 37°C and sutures are to dry for 70 hours at 60°C. The humidity content of the sutures has to be no higher than 500 ppm, which extends durability and work life of the sutures. Established sterilization and suture drying modes cannot change the structure and physical and mechanical properties of the polymer. Suture parameters meet the standards, which is very important for further suture utilizing as surgical suture materials.

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