Bacteria-killing implant material
Most modern implants are made of titanium – it is durable, bio-inert and not subject to corrosion. However, titanium does not have bioactive and antibacterial properties, and that is why scientists are actively working to create coatings that eliminate these shortcomings. A film of titanium oxide (TiO2) shows good results – because of the porous structure, it is most suitable for bone cell division, and the inclusion of calcium Ca and phosphorus P in its composition provides bioactivity. However, it is still an important task to give the implant antibacterial properties.
The team of the scientific and educational center for self-propagating high-temperature synthesis NITU “MISiS” (NUTS SVS NITU “MISiS”) has developed coatings for titanium implants based on titanium oxide with silver and platinum nanoparticles. The material developed by scientists allows accelerating proliferation, that is, active cell division by an average of 12-20%, as well as ensuring the destruction of up to 100% of bacteria after 72 hours and protection against the formation of a bacterial film.
“To create a titanium oxide film, we used various electrolytic solutions with varying contents of calcium and phosphorus – the“ native ”components of natural human bone. As a result of an experiment with three different electrolytes, samples were selected with the optimal composition (Ca = 6.3 and P = 4.8 atomic%), on the surface of which it was possible to obtain a structure with a relatively uniform pore diameter – from 0.7 to 2.3 micrometers . In itself, such a structure is already favorable for the propagation of osteoblast cells – this was verified after the samples were exposed in a solution that was similar in composition to blood plasma. We formed metal nanosized particles on the surface by implanting platinum ions of Pt and silver Ag in a vacuum chamber, ”says Viktor Ponomarev, postgraduate student at the Department of Powder Metallurgy and Functional Coatings of NUST“ MISiS ”.
Penetrating to a depth of approximately 30 nanometers in the sample, individual ions formed atoms. As a result of the high concentration of atoms in this layer, some of them came to the surface of the implant and formed silver and platinum nanoparticles. Silver on the surface is already independently capable of providing an antibacterial effect due to its ions. But there is their maximum concentration above which toxic properties may appear.
Platinum as an element does not have any bactericidal properties. The presence of Ag and Pt in the form of nanoparticles on the surface of titanium oxide gives the material catalytic properties. As a result, under ordinary light and ultraviolet radiation, coatings are able to generate a large number of reactive oxygen species that destroy various bacterial strains.
To check the antibacterial properties of the material, the samples were placed in media with various strains of E. coli and Staphylococcus aureus. The results obtained allowed us to conclude that the synergistic effect of silver ions and reactive oxygen species allows you to quickly and effectively eliminate any bacterial infection without threatening the patient. Samples with platinum nanoparticles destroy bacteria only thanks to reactive oxygen species.
In the future plans of scientists – to continue experiments to increase the bioactivity and bactericidal properties of implants. In particular, it is planned to saturate the open pores of titanium oxide with antibiotics, artificial blood and peptides.