Electron-beam treatment of bioresorbable Mg-Zn-Ga alloy devices for maxillofacial surgery: microbiological efficacy and SEM surface analysis

Relevance. Treatment of bioresorbable magnesium alloy devices before implantation must reduce microbial contamination without damaging the chemically reactive metal surface. Comparative data on gas-dynamic treatment, saturated steam treatment, and electron-beam irradiation of Mg-Zn-Ga alloy are limited. Objective. To compare residual microbial contamination after gas-dynamic treatment, saturated steam exposure, and electron-beam irradiation of Mg-Zn-Ga specimens artificially contaminated with Staphylococcus aureus, and to evaluate specimen surfaces before treatment, after irradiation, and after saturated steam treatment using scanning electron microscopy (SEM). Materials and methods. The study included 3 groups of 50 disk-shaped specimens (5 mm in diameter and 2 mm thick). A 0.1 mL aliquot of a suspension containing approximately 10 6 microbial cells/mL was applied to the surface of each disk. After drying, the specimens underwent gas-dynamic treatment (90 atm, 50–60°C, 45 min), saturated steam treatment (132–134 °C, 2 atm, 20 min), or electron-beam irradiation at 40 kGy. Rinsates were plated on egg-yolk salt agar and incubated at 37°C for 18–48 h, after which colony-forming units (CFU) were counted. Results. No growth was detected in 40/50 (80.0%), 43/50 (86.0%), and 41/50 (82.0%) samples, respectively (χ 2 =0.65; p =0.722). Across all 50 specimens in each group, mean CFU counts were 1.06, 0.58, and 0.52 per sample; among positive samples, the corresponding means were 5.3, 4.1, and 2.9. CFU count distributions were comparable across groups (Kruskal–Wallis test, H=0.65; p =0.724). SEM images showed that the irradiated specimen retained its original surface microtopography. After saturated steam treatment, SEM showed that the specimen surfaces were largely covered with corrosion products. Conclusion. All 3 treatment protocols resulted in low residual microbial contamination (mean, 0.52–1.06 CFU per sample). Electron-beam irradiation at 40 kGy preserved the original surface microtopography of the alloy, whereas saturated steam treatment left the surface covered with corrosion products. Electron-beam treatment in the final packaging is recommended for Mg-Zn-Ga devices because it preserves their surface.