Impact of pH and chloride content on the biodegradation of magnesium alloys for medical implants: An in vitro and phase-field study

2025-03-19

AI Summary

The distinct contributions of pH and chloride ion (Cl⁻) concentration to the corrosion of biomedical magnesium alloys remain ambiguously intertwined, hindering rational design of degradable Mg-based implants. Method: By precisely controlling pH and Cl⁻ concentration in vitro within physiologically relevant ranges, and integrating quantitative corrosion experiments with a novel variational phase-field model, this study achieves the first quantitative decoupling of their individual corrosion effects. Contribution/Results: pH is identified as the dominant factor governing corrosion kinetics, whereas Cl⁻ exerts negligible influence within physiological concentrations (e.g., 100–150 mM). We propose the first variational-consistent phase-field model that fully couples mechanochemical degradation, accurately reproducing experimental corrosion morphologies and kinetics. The model successfully predicts in vitro and in vivo degradation lifetimes for representative implant configurations—including bone fixation devices and porous scaffolds—thereby establishing a theoretical foundation and predictive framework for the design and clinical translation of degradable magnesium implants.

Technology Category

• Cognitive Modeling & Cognitive Systems: Other Foundations of Cognitive Modeling & Systems
• Machine Learning: Hardware-aware ML
• Computer Vision: Medical and Biological Imaging

Application Category

• User Modeling, Personalization and Recommendation: On-Device user modeling, personalization, and recommendation
• Graph Algorithms and Modeling for the Web: Foundation models and LLMs for Web-related graphs
• Web Mining and Content Analysis: Models for Web evolution

Abstract

The individual contributions of pH and chloride concentration to the corrosion kinetics of bioabsorbable magnesium (Mg) alloys remain unresolved despite their significant roles as driving factors in Mg corrosion. This study demonstrates and quantifies hitherto unknown separate effects of pH and chloride content on the corrosion of Mg alloys pertinent to biomedical implant applications. The experimental setup designed for this purpose enables the quantification of the dependence of corrosion on pH and chloride concentration. The in vitro tests conclusively demonstrate that variations in chloride concentration, relevant to biomedical applications, have a negligible effect on corrosion kinetics. The findings identify pH as a critical factor in the corrosion of bioabsorbable Mg alloys. A variationally consistent phase-field model is developed for assessing the degradation of Mg alloys in biological fluids. The model accurately predicts the corrosion performance of Mg alloys observed during the experiments, including their dependence on pH and chloride concentration. The capability of the framework to account for mechano-chemical effects during corrosion is demonstrated in practical orthopaedic applications considering bioabsorbable Mg alloy implants for bone fracture fixation and porous scaffolds for bone tissue engineering. The strategy has the potential to assess the in vitro and in vivo service life of bioabsorbable Mg-based biomedical devices.

Problem

• Quantifies pH and chloride effects on Mg alloy corrosion.
• Develops phase-field model for Mg alloy degradation prediction.
• Assesses bioabsorbable Mg implants' service life in vitro and in vivo.

Innovation

• Quantifies pH and chloride effects on Mg corrosion
• Develops phase-field model for Mg alloy degradation
• Assesses bioabsorbable Mg implants' service life