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22. Tailored Coatings for Enhanced Performance of Zinc–Magnesium Alloys in Absorbable Implants

Author

Hernández-Escobar, David, Pajares-Chamorro, Natalia, Chatzistavrou, Xanthippi, Hankenson, Kurt D., Hammer, Neal D., and Boehlert, Carl J.

Abstract

Absorbable metals exhibit potential for next-generation temporary medical implants, dissolving safely in the body during tissue healing and regeneration. Their commercial incorporation could substantially diminish the need for additional surgeries and complications that are tied to permanent devices. Despite extensive research on magnesium (Mg) and iron (Fe), achieving the optimal combination of mechanical properties, biocompatibility, and controlled degradation rate for absorbable implants remains a challenge. Zinc (Zn) and Zn-based alloys emerged as an attractive alternative for absorbable implants, due to favorable combination of in vivobiocompatibility and degradation behavior. Moreover, the development of suitable coatings can enhance their biological characteristics and tailor their degradation process. In this work, four different biodegradable coatings (based on zinc phosphate (ZnP), collagen (Col), and Ag-doped bioactive glass nanoparticles (AgBGNs)) were synthesized by chemical conversion, spin-coating, or a combination of both on Zn-3Mg substrates. This study assessed the impact of the coatings on in vitrodegradation behavior, cytocompatibility, and antibacterial activity. The ZnP-coated samples demonstrated controlled weight loss and a decreased corrosion rate over time, maintaining a physiological pH. Extracts from the uncoated, ZnP-coated, and Col-AgBGN-coated samples showed higher cell viability with increasing concentration. Bacterial viability was significantly impaired in all coated samples, particularly in the Col-AgBGN coating. This study showcases the potential of a strategic material-coating combination to effectively tackle multiple challenges encountered in current medical implant technologies by modifying the properties of absorbable metals to tailor patient treatments.

Published
2024
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38. Current status and perspectives of zinc-based absorbable alloys for biomedical applications

Author

Hernández-Escobar, David, Hermawan, Hendra, Champagne, Sébastien, Yilmazer, Hakan, Dikici, Burak, Boehlert, Carl J., Hernández-Escobar, David, Hermawan, Hendra, Champagne, Sébastien, Yilmazer, Hakan, Dikici, Burak, and Boehlert, Carl J.

Abstract

Absorbable metals have the potential to serve as the next generation of temporary medical implant devices by safely dissolving in the human body upon vascular tissue healing and bone regeneration. Their implementation in the market could greatly reduce the need of costly and risky additional surgeries for either implant replacement or removal, often required in current permanent implants. Despite the extensive research done over the last two decades on magnesium (Mg) and iron (Fe) based alloys, they have not generally shown a satisfactory combination of mechanical properties, biocompatibility and controlled degradation rate in the physiological environment. Consequently, zinc (Zn) based alloys were introduced in the last few years as alternative materials to overcome the limitations of Fe and Mg-based alloys. The blend of different alloying elements and processing conditions have led to a wide variety of Zn-based alloys having tunable mechanical properties and corrosion rates. This review provides the most recent progress in the development of absorbable Zn-based alloys for biomedical implant applications, primarily for cardiovascular and orthopedic devices. Their biocompatibility, processability and metallurgical aspects, as well as their mechanical behavior and corrosion properties are presented and discussed, including their opportunities, limitations and future research directions.

Published
2020

43. Current status and perspectives of zinc-based absorbable alloys for biomedical applications

Author

Hernández-Escobar, David, Champagne, Sébastien, Yilmazer, Hakan, Dikici, Burak, Boehlert, Carl J., Hermawan, Hendra, Hernández-Escobar, David, Champagne, Sébastien, Yilmazer, Hakan, Dikici, Burak, Boehlert, Carl J., and Hermawan, Hendra

Abstract

Absorbable metals have the potential to serve as the next generation of temporary medical implant devices by safely dissolving in the human body upon vascular tissue healing and bone regeneration. Their implementation in the market could greatly reduce the need of costly and risky additional surgeries for either implant replacement or removal, often required in current permanent implants. Despite the extensive research done over the last two decades on magnesium (Mg) and iron (Fe) based alloys, they have not generally shown a satisfactory combination of mechanical properties, biocompatibility and controlled degradation rate in the physiological environment. Consequently, zinc (Zn) based alloys were introduced in the last few years as alternative materials to overcome the limitations of Fe and Mg-based alloys. The blend of different alloying elements and processing conditions have led to a wide variety of Zn-based alloys having tunable mechanical properties and corrosion rates. This review provides the most recent progress in the development of absorbable Zn-based alloys for biomedical implant applications, primarily for cardiovascular and orthopedic devices. Their biocompatibility, processability and metallurgical aspects, as well as their mechanical behavior and corrosion properties are presented and discussed, including their opportunities, limitations and future research directions.

Published
2019

48. Microstructural evolution and intermetallic formation in Zn-Mg hybrids processed by High-Pressure Torsion.

Author

Hernández-Escobar, David, Rahman, Zia Ur, Yilmazer, Hakan, Kawasaki, Megumi, and Boehlert, Carl J.

Subjects
MICROSTRUCTURE, TORSION, HIGH pressure (Technology), INTERMETALLIC compounds synthesis, GRAIN size, METAL hardness
Abstract

High-pressure torsion (HPT) was used to investigate the synthesis of Zn-Mg hybrids by direct bonding of separate disks of Zn and Mg at room temperature under an applied pressure of 6.0 GPa after 1, 5, 15 and 30 turns. Microstructural characterisation of the HPT-processed disks showed the formation of a sub-micron multilayered structure embedded in a Zn-rich matrix with an average grain size of ∼ 600 nm at the disk periphery after 30 turns. XRD and TEM analysis revealed the presence of MgZn2 and Mg2Zn11 intermetallic compounds, which increased in volume fractions with increasing number of turns. The formation of these intermetallics, together with Hall-Petch strengthening, led to an exceptional increase of the hardness values after 15 turns. Electrochemical testing in simulated body fluid showed that the degree of plastic deformation had an impact on the corrosion resistance of the Zn-Mg hybrids, which would affect their implementation in the biomedical field for absorbable applications. This study confirmed that there is significant potential for using HPT in the joining of dissimilar metals at room temperature to form Zn-Mg hybrids containing ultrafine-grained metal-matrix heterostructures with enhanced hardness. [ABSTRACT FROM AUTHOR]

Published
2019
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