Table 1 Comparison of key properties between Zn-based and Mg-based biodegradable metals.
From: Alloying design of biodegradable zinc as promising bone implants for load-bearing applications
Key properties | Zn and Zn alloys | Mg and Mg alloys | |
|---|---|---|---|
Mechanical properties | Yield strength (YS), as extruded (MPa) | 126–389 | |
Ultimate tensile strength (UTS), as extruded (MPa) | 167–520 | ||
Compressive yield strength (CYS), as extruded (MPa) | 99–457 | ||
Elongation to failure, as extruded (%) | 6–84 | ||
Microhardness, as extruded | 44–217 (HV) | 35–90 (HB)62 | |
Elastic modulus (GPa) | 94–11063 | 41–4533 | |
Degradability | In vitro degradation rates (SBF, electrochemical test, mm year−1) | 0.16–1.66 | 0.45–12.5620 |
In vitro degradation rates (SBF, static immersion, 30–60 days, mm year−1) | 0.014–0.03 | 0.07–1.8820 | |
In vivo degradation rates (Rat femur model, 8–12 weeks, volume reduction, mm year−1) | 0.13–0.26 | 0.36–1.5820 | |
Degradation type | General corrosion, localized corrosion, pitting corrosion | Localized corrosion, pitting corrosion63 | |
Major cathodic reaction in neutral physiological environments | Oxygen reduction reaction35 | Hydrogen evolution reaction4 | |
Major gaseous degradation products | None | Hydrogen4 | |
Major soluble degradation products | Zn2+, OH− | Mg2+, OH− | |
Major solid degradation products and their solubility64 | Zn(OH)2 (Ksp = 5 × 10−17) ZnO (Ksp = 2.5 × 10−17) Calcium phosphates | Mg(OH)2 (Ksp = 8.9 × 10−12) MgO (Ksp = 2.37 × 10−8) Calcium phosphates | |
Biocompatibility | Essential elements on bone metabolism | Yes | Yes |
Human amount (g)6 | 2 | 25 | |
Serum concentration (mmol L−1)6 | 0.012–0.017 | 0.73–1.06 | |
Dietary average daily intake (mg)53 | 8.6 | 329 | |
Recommended daily intake (mg)53 | 12–15 | 280–350 | |
Beneficial effects on bone54 | Necessary for bone growth; Prevention of osteopenia and various skeletal abnormalities; Modulate bone turnover by stimulating osteoblast bone formation while inhibiting osteoclast differentiation; Increase bone strength | Necessary for bone growth; Prevention of skeletal fragility, osteoporosis, chronic chondrocalcinosis and myositis ossificans | |
Deleterious effects on bone6 | Hinder bone development at high concentration | None | |
IC50, osteoblast cells (mmol L−1) | 0.0955 | >4.02 (Mg2+ concentration in α-MEM)65 | |
IC50, endothelial cells (mmol L−1)66 | 0.13 | 66.7 | |
LD50 (mg kg−1)53 | 350 | 5000 | |
Osteogenesis | Yes | Yes | |
Osseointegration | Yes | Yes |
