Magnesium is an essential element for maintaining human life activities and can be obtained from food or magnesium supplements in daily life. Due to its high safety, light weight, and high production yield, magnesium materials can be used as implants for humans/animals in the medical field, such as bone fixation materials, skin repair materials, dental implant materials, and cardiovascular stent materials.

    Medical Metallic Materials

    The main types of medical materials include metallic materials, ceramic materials, polymer materials, and biological tissues. Biopolymer materials are currently the most mainstream in the biomaterials market, accounting for 49%, followed by metallic materials with a market share of 25%.

    Medical metallic materials are mainly used in implantable medical devices such as orthopedic, dental, and orthopedic implants and prostheses, various types of luminal stents represented by cardiovascular stents, and various surgical instruments and tools. The requirements for medical metallic materials used as implant materials are as follows:

1. Mechanical properties: Should have sufficient strength and      toughness, appropriate elasticity and hardness, good fatigue and creep      resistance, and necessary wear resistance and self-lubrication.
2. Corrosion resistance: Potential for electrolysis, pitting      corrosion, galvanic corrosion, wear corrosion, stress corrosion, etc.,      when exposed to the human physiological environment.
3. Biocompatibility: Must have excellent biocompatibility,      non-toxic, non-irritating, non-carcinogenic, non-mutagenic, and      non-rejection reactions to the human body, preferably with bioactivity.

    Currently, medical metallic materials used in clinical applications still have pain points such as non-degradability, harmful metal ion release, and lack of bioactivity. Traditional human implant materials like stainless steel and titanium alloys have excellent mechanical properties but are not degradable and absorbable, requiring secondary removal or permanent retention in the body after implantation. One of the development directions for new medical metallic materials is magnesium alloys. The complete degradability and outstanding biocompatibility of biodegradable medical magnesium alloy materials make them promising for widespread clinical application in hard tissue repair or replacement.

Characteristics and Advantages of Magnesium Materials

    Magnesium has a density of 1.74 g/cm³, and its alloys are the lightest engineering metal structural materials. Another common lightweight material is titanium alloy, with a density of 4.5 g/cm³. Compared to magnesium alloys, titanium alloys are about 2.5 times heavier, meaning that for the same shape, titanium alloys weigh about 2.5 times more than magnesium alloys.

    Magnesium plays a crucial role in human health. As a biomaterial, magnesium alloys have advantages such as good biocompatibility, degradability, and elastic modulus close to that of the human body, attracting attention and attempts from many scholars and enterprises in the medical field.

    Good biocompatibility: Magnesium is one of the essential trace elements for maintaining life activities in humans, animals, and plants. Magnesium exists in large quantities in bone tissue as Mg2+, and over 600 enzymatic reactions in the human body require magnesium as a cofactor, with more than 200 enzymes needing magnesium for activation. These biochemical reactions include protein synthesis, gene repair, energy metabolism, blood sugar control, blood pressure control, participation in muscle contraction and relaxation, affecting neuromuscular excitability transmission, and immune system regulation. About 53% of magnesium in the human body is stored in bones, 46% in muscles and soft tissues, and less than 1% in serum. The appropriate daily magnesium intake for adults is 300-400 mg. In modern diets dominated by processed foods, magnesium intake often falls below the minimum requirement. Long-term subclinical magnesium deficiency is one of the potential pathogenic mechanisms for many chronic clinical diseases, ranging from constipation, dysmenorrhea, and insomnia to heart disease, diabetes, and cancer.

    Excellent mechanical properties: The elastic modulus of magnesium metal is 41-45 GPa, which, as an orthopedic internal fixation material, can effectively reduce stress shielding effects and provide stable effects for the repair area.

Degradability: Magnesium has relatively high activity and a low standard electrode potential (-2.37 V), making it easy to corrode and degrade in biological environmental media to form magnesium ions, which participate in the organism's metabolism and are naturally excreted from the body. Magnesium ions in plasma are filtered and reabsorbed by glomeruli and renal tubules.

    Antibacterial properties: Pure Mg generates good antibacterial activity in vivo and in vitro mainly due to the increase in pH value during degradation. The antibacterial effect is primarily due to the increased osmotic pressure around bacterial cells caused by magnesium ions. However, due to the presence of biofilms, bacterial cells can withstand changes in external pH and cause tissue infections. Therefore, simply changing the pH value cannot achieve excellent antibacterial performance given the complex physiological environment of implants. Additionally, the degradation behavior of pure Mg in body fluids must be considered. If Mg corrodes too quickly, it not only produces high concentrations of Mg2+ ions, causing hypermagnesemia, but also generates large amounts of hydrogen gas.