Chemists from the Moscow state University together with colleagues from the SMRC AOA im. Bakuleva has developed and received a patent on a biological prosthesis of a heart valve, the surface of which is coated with nanodiamonds. Prosthesis made of synthetic material can work in the body for up to 20 years without replacement.
Today in the world of cardiac surgery are most commonly used prosthetic heart valves on the basis of bovine pericardium. To reduce the force of graft rejection and to increase the mechanical strength of the tissue, scientists stabilize dentures with glutaraldehyde. However, this technique has the side-effect free aldehyde groups, which are not contacted with the protein structure of the matrix, are development centres of calcification — deposits of calcium salts in tissues. The result of such a prosthesis fails after a while and required a new transplant.
Scientists have long been working on the creation of dentures, the lifespan of which would be of the order of several decades. To prevent calcification of the tissue surface the matrix of the graft need to modify. One of the ways that enables us to do is in the treatment of bovine pericardium with chitosan from water saturated with carbon dioxide at high pressure. Chitosan improves the efficiency, terms functioning in the body and the elasticity of the biological prosthesis, however, this material has a low strength.
To solve this problem, by combining the strength and durability of the prosthesis, managed by the Russian researchers. They have patented a biological prosthesis on the basis of bovine pericardium coated surface with a slurry of nanodiamonds. “First, the biological tissue has been produced by the experts SMRC AOA im. Bakuleva, — said one of the researchers, head of Department of radiochemistry and the Dean of chemical faculty, Moscow state University, corresponding member of RAS Stepan Kalmykov. — Then we applied on its surface "diamond coated" and measured material parameters — film thickness, uniformity of application of the slurry and so on. Followed by the test of strength”.
Nanodiamonds are nanoparticles, identical to the normal diamond. They have the same crystal lattice, but their sizes are in the several tens of nanometers. This material was created in Russia in the 1960-ies, but the practical application of him for a long time did not find. Only later, beginning in the 1990s, scientists in many countries began to investigate the biological properties of nanodiamonds. They found that the small carbon particle can be a means of targeted drug delivery.
Chemists from the Moscow state University also used these nanoparticles for their own purposes. They are created with nano-diamond powder aqueous suspension, which was immersed bovine pericardium. On the surface of the biological tissue graft nanodiamonds formed film, whichI gave the material extra strength while preserving its elasticity and S-shaped curve stress–strain. This shows that the material has sufficiently good strength characteristics. Nanodiamonds coated with the biomaterial does not lose its mechanical properties, its young’s modulus was about 30 MPa, as for the source material, while the tensile strength increases up to 9-10 MPa, compared to 6 MPa for the original material.