Zn-Li alloy after extrusion and drawing: Structural, mechanical characterization, and biodegradation in abdominal aorta of rat

- Tensile strength of pure zinc is increased 2-2.5 times by addition of ~ 0.1 wt% Li.
- Zn-Li alloy degrades at a rate of 0.01-0.05 mm/yr in 12 months in abdominal aorta of rat.
- In vivo biocompatibility study over 11 months indicate moderate inflammation with non-obstructive neointima formation.

Zinc shows great promise as a bio-degradable metal. Our early in vivo investigations implanting pure zinc wires into the abdominal aorta of Sprague-Dawley rats revealed that metallic zinc does not promote restenotic responses and may suppress the activities of inflammatory and smooth muscle cells. However, the low tensile strength of zinc remains a major concern.A cast billet of the Zn-Li alloy was produced in a vacuum induction caster under argon atmosphere, followed by a wire drawing process. Two phases of the binary alloy identified by x-ray diffraction include the zinc phase and intermetallic LiZn4 phase. Mechanical testing proved that incorporating 0.1 wt% of Li into Zn increased its ultimate tensile strength from 116 ± 13 MPa (pure Zn) to 274 ± 61 MPa while the ductility was held at 17 ± 7%. Implantation of 10 mm Zn-Li wire segments into abdominal aorta of rats revealed an excellent biocompatibility of this material in the arterial environment. The biodegradation rate for Zn-Li was found to be about 0.008 mm/yr and 0.045 mm/yr at 2 and 12 months, respectively.

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