Why doesn’t the human body reject titanium alloys? Why does it repel other metals?
2025,07,28
The metals put into the human body in medicine are all titanium alloys. Titanium is the only metal that the human body does not reject. Why doesn't it reject it? Is there any connection between titanium metal and human body composition?
First of all, the so-called rejection means that the immune system recognizes foreign proteins and is labeled by antibodies, which then triggers an inflammatory response. Immune cells will gather, phagocytose and degrade foreign cells and viruses.
In addition, the main danger of metals in the body is the corrosion of metals by body fluids. Some metal ions+ may be cytotoxic.
The biggest advantage of titanium is that it can form a high-quality oxide film at room temperature, in the air and in water, completely preventing titanium ions+ from entering the body. The titanium oxide film is almost completely non-corroded in the body. This is the so-called tissue compatibility.
Not only in the human body, but also in the strong acid and alkali environment of the chemical industry, and in the strong salt corrosion environment of the deep sea industry, only titanium alloys can play the important role of structural metals and resist corrosion in various harsh environments.
In fact, the metals tantalum+ and niobium are similar to titanium in the body, but they are more expensive than titanium and their machining performance is not necessarily better, so they are not used much.
Titanium alloys are widely used in the human body because
1. Biocompatibility:
The biocompatibility of titanium alloys mainly comes from the naturally formed titanium oxide layer on its surface. This oxide film is very stable and can effectively prevent metal ions from being released into the body, thereby reducing immune responses. The inertness of the titanium oxide layer means it barely reacts with biological tissue or fluids in the body, further reducing the potential for rejection and inflammation.
2. Density/mechanical properties:
The strength and toughness of Titanium Alloy make it an ideal orthopedic implant material, with a density similar to human bone. These physical properties are similar to human bone and help reduce stress mismatch between implant and bone.
3. Corrosion resistance:
Titanium alloy has extremely high corrosion resistance in the human body. This is because the titanium oxide layer prevents body fluids from coming into direct contact with the metal, reducing corrosion and preventing the release of metal ions.
4. Non-magnetic:
The non-magnetic nature of titanium means the implant will not interfere with diagnostic procedures such as magnetic resonance imaging (MRI).
Due to these properties of titanium alloy, human cells will grow along the titanium alloy and eventually "grow" together with the titanium alloy.
