Table 7.
In vivo corrosion and biocompatibility of biodegradable Zn and Zn alloys.
| Materials | Animal model (implanted site) | Duration (months) | Corrosion rate (mm/y) | Residual area (vol%) | Biocompatibility | Key findings | Refs. | |||
|---|---|---|---|---|---|---|---|---|---|---|
| Pure Zn | ||||||||||
| Zn (wire) | SD rat (aorta) | 1.5 | 0.012 | 97 | ♦♦♦ | Zn wire remained intact up to 4 months and then corrosion accelerated. The corrosion products on Zn after 4.5 and 6 months were mainly made of ZnO and ZnCO3. | [78] | |||
| 3.0 | 0.02 | 93 | ||||||||
| 4.5 | 0.042 | 76 | ||||||||
| 6.0 | 0.048 | 63 | ||||||||
| SD rat (aorta) | 2.5 | – | – | ♦♦♦ | Low cell densities and neointimal tissue thickness, along with tissue regeneration within the corroding implant, point to optimal biocompatibility of corroding zinc | [282] | ||||
| 6.5 | – | – | ||||||||
| ZnExt&Dwg (wire) | SD rat (aorta) | 2 | 0.020 | 95 | ♦♦♦ | Extruded Zn wire exhibited nearly linear relationship between the % of area reduction (AR) and time, and uniform gradual acceleration of biodegradation and moderate inflammation with nonobstructive neointima. | [101] | |||
| 4 | 0.030 | 85 | ||||||||
| 6 | 0.019 | 85 | ||||||||
| 8 | 0.035 | – | ||||||||
| 10 | 0.016 | – | ||||||||
| 12 | 0.023 | 69 | ||||||||
| Zn (wire) | SD rat (aorta) | 3 | 0.020 | 92 | ♦♦♦ | Zn wires exhibited steady corrosion without local toxicity for up to at least 20 months post implantation, despite a steady build-up of passivating corrosion products and intense fibrous encapsulation of the wire. | [283] | |||
| 6 | 0.019 | 85 | ||||||||
| 9 | 0.019 | 79 | ||||||||
| 12 | 0.023 | 70 | ||||||||
| 14 | 0.019 | 70 | ||||||||
| 20 | 0.026 | 47 | ||||||||
| ZnExt (rod) | SD rat (femur) | 2 | 0.137 | 95 | ♦♦♦ | Dark brown degradation products spread into the surrounding tissue with newly formed woven bone dispersed in it. | [213] | |||
| Zn Alloyed with nutrient elements (Ca, Mg and Sr) | ||||||||||
| Zn-1CaHR (pin) | Mice (femur) | 2 | 0.190 | – | ♦♦ | Promoted bone growth. | [147] | |||
| Zn-0.8CaHE (rod) | SD rat (femur) | 2 | 0.130 | 95 | ♦♦ | A greater amount of new bone tissues (NBTs) were observed surrounding the implants and the osteocytes in the new bone tissue arranged in an organized way. | [213] | |||
| Zn-0.002MgHE + DW (wire) | SD rat (aorta) | 1.5 | 0.029 | 95 | ♦♦♦ | Zn–Mg alloys displayed uniform degradation and the increase of degradation rates in later stages of implantation was detected. Slightly decrease in biocompatibility with increasing Mg content was observed. | [151] | |||
| 3 | 0.020 | 92 | ||||||||
| 4.5 | 0.027 | 85 | ||||||||
| 6 | 0.033 | 77 | ||||||||
| 11 | 0.051 | 43 | ||||||||
| Zn-0.005MgHE + DW (wire) | SD rat (aorta) | 1.5 | 0.021 | 96 | ♦♦ | |||||
| 3 | 0.020 | 93 | ||||||||
| 4.5 | 0.023 | 87 | ||||||||
| 6 | 0.030 | 78 | ||||||||
| 11 | 0.039 | 54 | ||||||||
| Zn-0.08MgHE + DW (wire) | SD rat (aorta) | 1.5 | 0.012 | 98 | ♦♦ | |||||
| 3 | 0.013 | 95 | ||||||||
| 4.5 | 0.015 | 91 | ||||||||
| 6 | 0.027 | 80 | ||||||||
| 11 | 0.023 | 71 | ||||||||
| Zn-0.8MgHE (rod) | SD rat (femur) | 2 | 0.146 | 95 | A lot of NBTs were observed surrounding the implants with no signs of osteolysis, deformity or dislocation. | [213] | ||||
| Zn-1MgHR (pin) | Mice (femur) | 2 | 0.170 | – | ♦♦♦ | Promoted bone growth. | [147] | |||
| Zn–1Mg-0.1CaHE (rod) | SD rat (subcutaneous) | 3 | 0.050 | – | ♦♦ | Zn–Mg–Ca alloys could be safely used by adding Mg to adjust the degradation property. | [180] | |||
| Zn-0.02 Mg-0.02CuHE + DW (stent) | New Zealand rabbits (artery) | 1 | 0.078 | 83 | ♦♦♦ | The stent corroded slowly, and no obvious intimal hyperplasia was observed till 6 months. After that corrosion accelerated. In addition, no obvious thrombosis and systemic toxicity during implantation period were observed. | [165] | |||
| 3 | 0.027 | 83 | ||||||||
| 6 | 0.023 | 71 | ||||||||
| 12 | 0.040 | 42 | ||||||||
| Zn-2.5Mg-2.5FeHE + DW (rod) | Beagle dogs (dorsal) | 1 | 0.033 | – | ♦♦ | Zinc-based alloy osteosynthesis system possessed uniform and slow corrosion leading to adequate degradation behavior in 6 months. | [87] | |||
| 3 | 0.078 | – | ||||||||
| 6 | 0.094 | – | ||||||||
| Zn-0.1SrHE (rod) | SD rat (femur) | 2 | 0.127 | 95.5 | ♦♦ | A great proportion of NBTs were observed surrounding the implants. | [213] | |||
| Zn-1SrHR (pin) | Mice (femur) | 2 | 0.220 | – | ♦♦ | Promoted bone growth. | [147] | |||
| Zn-1.1SrHR (wire) | SD rat (aorta) | 1 | – | – | ♦♦ | New bone formation was observed around the implant. Also, some fibrotic and collagenous tissues between the implants and newly formed bones were also observed. | [216] | |||
| Zn Alloyed with crucial elements (Cu, Fe and Mn) | ||||||||||
| Zn-0.4CuHE (rod) | SD rat (femur) | 2 | 0.250 | 92 | ♦♦ | Dark brown degradation products spread into the surrounding tissue with newly formed woven bone dispersed in it. | [213] | |||
| Zn-0.8CuCast (stent) | White pigs (artery) | 3 | – | 92 | ♦♦ | Stent provided sufficient structural support and exhibited an appropriate degradation rate during 24 months of implantation without degradation product accumulation, thrombosis, or inflammation response. | [285] | |||
| 6 | – | 79 | ||||||||
| 9 | – | 77 | ||||||||
| 12 | – | 74 | ||||||||
| 18 | – | 56 | ||||||||
| 24 | – | 28 | ||||||||
| Zn-0.4FeHE (rod) | SD rat (femur) | 2 | 0.150 | 94.5 | ♦♦ | Dark brown degradation products spread into the surrounding tissue with newly formed woven bone dispersed in it. | [213] | |||
| Zn-1.3FeCast (disk) | Wistar rat (subcutaneous) | 3.5 | 0.115 | – | ♦♦ | The implantation of alloy did not increase the amount of zinc in blood beyond the acceptable level and there were no signs of infection. | [230] | |||
| Zn-2FeCast (disk) | Wistar rat (subcutaneous) | 3.5 | 0.115 | – | ♦♦ | No signs of anemia, inflammation or necrosis. | [284] | |||
| 6.0 | 0.055 | – | ||||||||
| Zn-0.1MnHE (rod) | SD rat (femur) | 2 | 0.127 | 96 | ♦♦ | New bone tissues were observed surrounding the implants. Osteocytes in the new bone tissue arranged in organized way. | [213] | |||
| Zn Alloyed with other elements | ||||||||||
| Zn-1AlHR (strips) | SD rat (aorta) | 1.5 | – | 83 | ♦♦ | The alloys showed acceptable biocompatibility with surrounding arterial tissue. No necrotic tissue was detected, while some inflammation was observed. Biocorrosion rates were higher at initial stages than that of pure Zn. | [288] | |||
| 3 | – | 81 | ||||||||
| 4.5 | – | 66 | ||||||||
| 6 | – | 50 | ||||||||
| Zn-3AlHR (strips) | 1.5 | – | 67 | ♦♦ | ||||||
| 3 | – | 66 | ||||||||
| 4.5 | – | 62 | ||||||||
| 6 | – | 52 | ||||||||
| Zn-5AlHR (strips) | 1.5 | – | 89 | ♦♦ | ||||||
| 3 | – | 75 | ||||||||
| 4.5 | – | 67 | ||||||||
| 6 | – | 57 | ||||||||
| Zn-2AgHE (rod) | SD rat (femur) | 2 | 0.187 | 93.5 | ♦♦ | A localized degradation mode was observed with new bone formation and direct contact between new bone and implants at 8 weeks. | [213] | |||
| Zn-0.1LiHE + DW (wire) | SD rat (aorta) | 2 | 0.008 | 98 | ♦♦ | The alloy degraded ~ 30% of its original volume after 12 months and revealed almost linear relationship with the % of AR and time, indicating uniform gradual acceleration of biodegradation. Medium inflammation with non-obstructive neointima was observed. | [101] | |||
| 4 | 0.016 | 92 | ||||||||
| 6.5 | 0.019 | 86 | ||||||||
| 9 | 0.038 | 79 | ||||||||
| 12 | 0.045 | 70 | ||||||||
| Zn-0.4LiHE (rod) | SD rat (femur) | 2 | 0.156 | 93.5 | ♦♦ | Implant maintained its integrity at 8 weeks and degraded uniformly. Larger amounts of NBTs were observed surrounding the implants. | [213] | |||
SD rat: Sprague–Dawley rat; biocompatibility rating: ♦♦♦- excellent, ♦♦- good, ♦- poor.