Study of biocompatibility <i>in vitro</i> of ultrafine-grained Zn-based bioresorbable alloys

Abstract

Background. Zinc alloys have advantages for use as biodegradable implantable orthopedic metal structures due to the absence of gas formation in comparison with magnesium alloys. But their mechanical properties are often has lower values.Aim. Investigation of effect of high-pressure torsion (HPT) on strength, ductility, corrosion resistance, antimicrobial properties, surface cell colonization and biocompatibility of Zn-based alloys.Materials and methods. The alloys of the Zn-x%Mg system (where x = 0; 1 and 1.7 %) in the initial undeformed state and after HPT were investigated in this work. Mechanical properties were studied on an Instron 3382 testing machine at room temperature. The biocompatibility of the alloys was evaluated by hemolytic activity and cytotoxicity assesment. We also studied the stimulation of colonization of the surface of the samples by mesenchymal multipotent stromal cells, as well as the presence of antimicrobial properties relative to the Escherichia coli culture. To study the degradation rate, the alloy samples were incubated in a standard nutrient medium for 8 days, assessing the change in their mass relative to the initial value.Results. It has been established that HPT leads to an increase in the strength of pure Zn 2 times, and of Zn-1%Mg and Zn-1.7%Mg alloys by 3 and 5.5 times, respectively, with an increase in their ductility. At the same time, deformation treatment has practically no effect on the corrosion resistance of the initial materials. No significant increase in the hemolytic activity and bactericidal activity of the alloys was revealed during studies. However, a significant decrease in the ability of cells to colonize the surface of pure zinc was observed after HPT.Conclusion. HPT leads to a significant increase in the strength and ductility of studied materials. At the same time, a decrease in the biocompatibility of zinc-based alloys after HPT did not observed. It was found that the discovered cytotoxic effect was obviously caused not so much by the alloy processing method as by its chemical composition. This makes it possible to evaluate the studied alloys of the Zn-x%Mg system treated by HPT (and, in particular, the Zn-1.7%Mg alloy) as a promising structure for the development of biodegradable orthopedic products.