The influence of buffer system and biological fluids on the degradation of magnesium

Corrosion Behavior in Magnesium-Based Alloys for Biomedical Applications

Magnesium alloys exhibit superior biocompatibility and biodegradability, which makes them an excellent candidate for artificial implants. However, these materials also suffer from lower corrosion resistance, which limits their clinical applicability. The corrosion mechanism of Mg alloys is complicated since the spontaneous occurrence is determined by means of loss of aspects, e.g., the basic feature of materials and various corrosive environments. As such, this study provides a review of the general degradation/precipitation process multifactorial corrosion behavior and proposes a reasonable method for modeling and preventing corrosion in metals. In addition, the composition design, the structural treatment, and the surface processing technique are involved as potential methods to control the degradation rate and improve the biological properties of Mg alloys. This systematic representation of corrosive mechanisms and the comprehensive discussion of various technologies for applications could lead to improved designs for Mg-based biomedical devices in the future.

Biodegradable Magnesium Biomaterials—Road to the Clinic

In recent decades, we have witnessed radical changes in the use of permanent biomaterials. The intrinsic ability of magnesium (Mg) and its alloys to degrade without releasing toxic degradation products has led to a vast range of applications in the biomedical field, including cardiovascular stents, musculoskeletal, and orthopedic applications. With the use of biodegradable Mg biomaterials, patients would not suffer second surgery and surgical pain anymore. Be that as it may, the main drawbacks of these biomaterials are the high corrosion rate and unexpected degradation in physiological environments. Since biodegradable Mg-based implants are expected to show controllable degradation and match the requirements of specific applications, various techniques, such as designing a magnesium alloy and modifying the surface characteristics, are employed to tailor the degradation rate. In this paper, some fundamentals and particular aspects of magnesium degradation in physiological environments are summarized, and approaches to control the degradation behavior of Mg-based biomaterials are presented.

Characterization and Biocompatibility of Insoluble Corrosion Products of AZ91 Mg Alloys

Biodegradable Mg alloys have good bioactivity and suitable mechanical properties, which is desirable for application in the clinical fields. However, the biocompatibility of Mg alloys during the degradation process has always been a concern. In this paper, the corrosion behavior of AZ91 alloys in a simulated cell culture environment was studied, especially the insoluble corrosion product during the degradation was characterized, and the biocompatibility of the insoluble corrosion products was evaluated. The results of immersion test showed that the corrosion rate of the AZ91 alloy was low under the condition of high CO₂ and humidity, especially in phosphate-buffered saline. Moreover, the insoluble corrosion product was MgCO₃·3H₂O, which showed a needle-like, circular aggregated, and square-radial feature. Meanwhile, MgCO₃·3H₂O showed poor cell biocompatibility by increasing the pH and Mg²⁺ content of the culture solution, which may affect the biocompatibility of Mg alloys.

Magnesium degradation under physiological conditions - Best practice

This review focusses on the application of physiological conditions for the mechanistic understanding of magnesium degradation. Despite the undisputed relevance of simplified laboratory setups for alloy screening purposes, realistic and predictive in vitro setups are needed. Due to the complexity of these systems, the review gives an overview about technical measures, defines some caveats and can be used as a guideline for the establishment of harmonized laboratory approaches.

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Physiological conditions are mandatory for mechanistic understanding of magnesium degradation.

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Guidelines and caveats for experimental setups are reviewed.

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Media composition is essential for reliable experiments.