MISiS: Biocompatible alloy for bone replacement

Main article: Bone implantation

2023: Obtaining a patent for an alloy based on the iron-manganese-silicon system

Scientists at MISIS University have patented a shape memory alloy for biodegradable bone implants based on the iron-manganese-silicon (Fe-Mn-Si) system. It has high biomechanical compatibility with bone tissue and the required dissolution rate, making it a promising material for use in traumatology, orthopedics and maxillofacial surgery. This was announced on October 18, 2023 by the university.

There are materials based on magnesium or zinc that can dissolve in the body, but they have lower mechanical properties. In addition, the rate of magnesium biodegradation is excessively high, which can lead to a violation of the integrity of the fixing implant until the bone tissue is fully restored. Also, the decay of magnesium is accompanied by the release of hydrogen gas, which can harm humans. Compared to these substances, iron-based alloys have better mechanical properties but low biodegradability. Manganese and silicon are used as alloying elements to eliminate this drawback.

The development of biodegradable implants is an urgent trend in medicine. This is due to the fact that in some cases, after the damaged bone tissue is restored, the implants must be removed from the body and repeated surgery must be performed. This is traumatic for the patient and comes with additional costs. Moreover, the use of stainless steel implants, cobalt-chromium, titanium alloys and other traditional materials in the long term can lead to negative consequences: loosening of the implant, its wear and tear, restriction of bone growth, allergic reactions, and in some cases even to oncological diseases, - said the author of the patent Ph.D. Pulat Kadirov, engineer of the Department of Metal Forming NUST MISIS.

In addition to biocompatibility with bone tissue and certain physical and mechanical properties, the material for implants should contribute to the healing and regeneration of tissues, followed by natural dissolution in the patient's body.

In the development of biodegradable alloys, an important task is to correctly adjust their dissolution rate to ensure a high level of mechanical properties during the required time until the bone tissue has recovered and the implant is heavily stressed. Therefore, in the course of research, we study in detail both the mechanical and corrosion-electrochemical behavior of our materials, - said the co-author of the patent, Ph.D. Yulia Zhukova, leading researcher at the Center for Nanomaterials and Nanotechnology at MISIS University.

It is known that the use of various thermomechanical processing techniques, including hot and cold rolling with post-deformational annealing, significantly improves the functional properties of the alloy. Scientists have found that after hot rolling at 800 ° C with subsequent cooling into water, the best biomechanical compatibility of the material with bone tissue is achieved, such mechanical properties as tensile strength, yield strength, elongation to fracture, as well as the required biodegradation rate - 0.47 mm/year.

NUST MISIS specialists plan to scale the production of blanks of this alloy for industrial production while maintaining all the required qualities. Also, within the framework of the agreement with the Research Institute of Oncology of the Tomsk National Research Medical Center of the Russian Academy of Sciences, medical preclinical tests of biocompatibility in vitro and in vivo will be held by the end of 2023.

2022: Development of a superelastic alloy to replace bone tissue

Russian materials scientists from NUST MISIS have developed a biocompatible alloy based on titanium, zirconium and niobium, which has physical and mechanical properties close to bone tissue. The resulting alloy can become the basis for bone implants. The results of the project are published in the journal Metals. This was announced on March 15, 2022 by NUST MISIS.

Metal biomaterials play a special role in bone tissue reconstruction. One of them is titanium. Showing biochemical inertia due to the surface oxide film, however, it does not correspond to the physicomechanical properties of the bone, which leads to shielding (removal) of stresses and embrittlement of nearby bone tissues.

The solution to this problem is the creation of metal alloys capable of reproducing the behavior of the replaced bone under load. Such alloys should show superelasticity - the ability to reversibly accumulate significant stresses (spring). To obtain superelasticity, it is necessary to accurately select the phase composition of the alloy at room temperature, which is possible by adjusting the chemical composition of the alloy.

"In our work, we studied the structure and functional properties of several alloys of the Ti-Zr-Nb system with increased zirconium content. It was expected that changing the ratio of these elements should help find the optimal phase composition, which will lead to pronounced superelasticity at room temperature, "- Danil Barilyuk, graduate student of the iPhD "Biomaterial Science" NUST "MISIS" told.

According to the developers, during the work, samples of four alloys of the Ti-Zr-Nb system with different percentages of zirconium and niobium were obtained. Their microstructure and mechanical properties were carefully studied and analyzed.

"An alloy with a Ti-41% Zr-12% Nb composition showed high ductility with elongation to fracture of more than 20%, and the total reversible deformation of the alloy was more than 6%. The obtained results indicate that this material is one of the most promising superelastic alloys in the Ti-Zr-Nb system, "- concluded Danil Baryluk.

In mid-March 2022, the scientific team continues a series of tests in order to optimize the technology for obtaining an alloy for industrial import-substituting use.

"A consortium" Health Engineering "has been created at NUST" MISIS, "one of the tasks of which is to train scientists who are developing at the junction of materials science, biology and medicine. We involve students in the implementation of research in the development of new methods for the diagnosis and treatment of severe diseases, the creation of medical devices, "- explained Fyodor Senatov, Ph.D., Director of the REC of Biomedical Engineering, Head of the Educational Program iPhD "Biomaterial Science" NUST "MISIS."