Kazan University continues working on improving properties of implants
A joint Russian-Italian-Romanian research was published in Nanomaterials.
The team comprises scientists from the Institute of Metallurgy and Materials Science (Russian Academy of Sciences, Moscow), Moscow State University, First Moscow State Medical University, Institute of Theoretical and Experimental Biophysics of the Russian Academy of Sciences (Pushchino), Kazan Federal University with colleagues from the Experimental Institute of Zoological Prevention for the Regions of Lazio and Tuscany (Italy), the National Research Council (Italy) and the Polytechnic University of Bucharest (Romania).
As Assistant Lecturer, co-author Fadis Murzakhanov explains, calcium phosphate compounds are usually taken as the basis for synthetic bone implants, since they are similar to those found in the human body. Cations of the rare earth element gadolinium (Gd3+) are often used in ceramic-based synthetic materials, especially as coatings, because they are characterized by high chemical stability, increase the biocompatibility of nanoparticles in the coating composition, and reduce the possible toxicity of drugs.
The gist of this project is to modernize ceramic materials which are the basis for bone implants. The improvement of medicine makes it necessary to constantly improve the various properties of the materials from which implants are made, in particular, antibacterial properties, thermal stability (ceramics should not be destroyed during annealing), etc.
The advantage of the obtained material with gadolinium ions can be considered the ability to better track the survival rate of the implant, Murzakhanov says.
“Gadolinium plays the role of an internal contrast agent. It is needed so that implant survival can be more effectively monitored using MRI and CT. Ions of manganese, aluminum, iron improve the properties of the implant, but we cannot understand exactly how it takes root. It is through gadolinium that we can track the stages of healing, find out if there is rejection, etc. Thus, gadolinium improves the way imaging is obtained – greatly improves the image quality on MRI images. At the same time, the introduction of gadolinium did not lead to the formation of toxicity and did not violate the biocompatibility of the material – all biological properties were preserved,” he describes.
The main contribution of Kazan University in this project is the analysis of the structure of the obtained sample.
“Scientists from the Institute of Physics studied the structure of tricalcium phosphate. We introduced a gadolinium ion into the sample and studied whether it was embedded in the structure and how it affects other ions, in particular, and the crystal structure of the material as a whole,” Murzakhanov continues. “After our fellow chemists synthesized the material, we confirmed that the ion occupied one of the calcium positions in the sample structure, as well as the absence of other side phases, which indicates the purity of the material.”
According to the interviewee, gadolinium ions were successfully incorporated into tricalcium phosphate.
“It was quite a complex procedure, given that the gadolinium ion is trivalent and at the same time occupies the position of divalent calcium. There was a possibility that he would not enter the structure. But we showed that it was introduced into the structure and no side phases were formed,” he adds.
In their work, scientists used electron paramagnetic resonance in a pulsed mode. A two-dimensional experiment was also carried out to study weak electron-nuclear interactions.
The relevance of the topic is confirmed by current data from the World Health Organization. Approximately 1.71 billion people in the world suffer from disorders and diseases of the musculoskeletal system. They are also a leading reason of disability in the world. Murzakhanov says that his work on improving the properties of implants continues: experiments are being carried out with the introduction of several ions, including manganese, iron, and strontium. In addition, there are prospects for the creation of a biphasic material to improve the control over the rate of resorption of implants.
“We already have previous experience with the study of materials with a single impurity. Now, based on our results, we are investigating new samples with several impurities. This leads to new interesting properties of materials – some impurity ions enhance the antibacterial effect, other ions increase thermal stability, etc. Much also depends on the concentration of these impurities. In addition, there is the prospect of not only introducing different ions into one material, but also combining several materials into a biphasic material. Among the possible options is a combination of tricalcium phosphate and hydroxyapatite, which will allow controlling the rate of implant resorption. Materials based on calcium phosphates dissolve in the body and are replaced by human bone tissue,” the co-author concludes. “Gradually, human bone tissue comes to replace implants. But it is important to control the speed so that the implant material does not dissolve faster than the bone grows together, and the bone union should not outstrip the resorption. Ideally, the material for the implant should be such that it does not reject and that it has a porous structure, which activates healing. It is important that the implant stimulates bone growth, healing, and a smooth replacement of the implant with bone tissue occurs.”
Influence of Synthesis Conditions on Gadolinium-Substituted Tricalcium Phosphate Ceramics and Its Physicochemical, Biological, and Antibacterial Properties