RO123356B1 - Biocompatible thin-layer materials for coating niti and nitinb shape-memory alloys - Google Patents

Abstract

The invention relates to biocompatible thin-layer materials as single-layer or multi-layer laminate meant to be used for coating NiTi and NiTiNb-type shape-memory alloys employed in making implants or surgical devices. According to the invention, the materials are made of alternating individual thin-layers of either ZrN and TiN, or ZrN and TiAlN, or ZrON and TiON, or ZrON and TiAlON, where the thickness of the pairs of thin layers ranges between 5...400 nm and the total thickness ranges between 0.6...4 μ m, the thickness ratio of the individual layers (ZrN)/(TiN) and (ZrN)/(TiAlN) ranging between 0.25...4 and (ZrON)/(TiON) and (ZrON)/(TiAlON) between 1...4, respectively, at an Al/Ti ratio in the TiAlN and TiAlON layers in the range of 0.4...1 and an O/N ratio in the ZrON, TiON and TiAlON layers in the range of 1...4, the amount of ions released in Ringer corrosive solution being of less than 50 μ g/cmand in Carter-Brugirard solution of less than 40 μ g/cm, the corrosion rate being lower than 0.5x10mm/year and the cellular viability factor upon cytotoxicity assay being higher than 65%.

Description

The invention relates to materials of thin layers, biocompatible, in the form of monolayers or multilayers, corrosion resistant, adherent to the support on which they are deposited and which are used for coating alloys with shape memory, NiTi and NiTiNb type, used for making implants and biomedical devices used in surgery.

A wide variety of shape memory materials are known, but in biomedical applications the alloys from the Ni-Ti group are most frequently used, because they combine good mechanical properties with those of shape memory. The disadvantage of these materials is that they contain a large amount of nickel that induces a toxic and allergic response in contact with the tissue adjacent to the implant. The biggest problems related to the use of shape memory alloys in biomedical applications, such as orthodontic and cardiovascular devices, endodontic piles, spine rods, stitches, stents, are due to products resulting from corrosion that give inflammatory reactions as a result of contact. with the skin, osteoblast cells or vascular muscle cells.

The application of the invention removes the disadvantages mentioned in that the multilayer material consists of alternating thin layers of ZrN and TiN or ZrN and TiAIN or ZrON and TiON or ZrON and TiAION, having the thicknesses of the pairs of thin layers between 5 ... 400 nm and total thicknesses between 0.6 ... 4 pm, a ratio of the thickness of the individual layers ZrN / TiN and ZrN / TiAIN between 0.25 and 4 respectively ZrON / TiON and ZrON / TiAION between 1 and 4, a ratio Al / Ti in the layers of TiAIN and TiAION between 0.4 and 1 and an O / N ratio in the layers ZrO, TiON and TiAION between 1 and 4.

In order to increase the corrosion resistance and decrease the nickel concentration released from shape memory alloys, various technologies have been used to improve the quality of surfaces by heat, thermochemical or thin layer deposition, so that the shape memory properties do not be affected.

As coating materials, chosen for the present invention, titanium nitride and oxynitride, aluminum and titanium nitride and oxynitride, zirconium nitride and oxynitride, and combinations thereof were used. The invention relates to monolayer biocompatible materials of type ZrON, TiON and TiAION and to multilayer biocompatible materials of type (ZrN) / (TiN), (ZrN) Z (TiAIN), (ZrON) / (TiON) and (ZrON) Z ( TiAION).

The technical problem solved by the invention is the realization of thin protective layers, in the form of mono and multilayer materials with biocompatible properties, resistant to corrosion and wear, which determine the increase of the lifetime of TiNi and TiNiNb alloy implants and the decrease of the amount of toxic ions released compared to uncovered implants, without affecting the memory properties of their shape.

The superior properties of biocompatible mono and multilayer materials, which are the subject of the invention, are generated by their resistance to the corrosive action of fluids in the human body, by the use in the composition of the coating material of elements that do not cause adverse reactions.

Compared to the monolayers, in the case of multilayers there is a decrease in the mechanical stresses developed in the coating material due to the alternation of the individual layers in the deposition structure.

The multilayer nitride materials according to the invention are made of alternating individual thin layers, either ZrN and TiN, or ZrN and TiAIN, with total thicknesses between 0.6 and 4 μm. The thicknesses of the thin layer pairs are between 5 and 400 nm, with the ratio of the thicknesses of the individual layers (ZrN) / (TiN) and (ZrN) / (TiAIN) between 0.25 and 4. The alternating thin layers of ZrN and TiN and TiAIN are quasi-stoichiometric (0.9 <N / Zr <1.1; 0.9 <N / Ti <1.1; 0.9 <N / (Ti + AI) <1.1) and with an Al / Ti ratio in TiAIN layers between 0.4

EN 123356 Β1 and 1. Multilayer materials have a high adhesion to the substrate, the critical normal forces at 1 scratch test being 45 ... 52 N. Multilayer materials have microdurities between 30 .. .35 GPa, the amount of ions released in Ringer 3 corrosive solution at 37 ° C is <50 pg / cm ² , and in Carter-Brugirard corrosive solution at 37 ° C is <40 pg / cm ² , falling (according to ISO 8044) in the class perfectly stable resistance. The 5 multilayer materials have a corrosion rate <0.5x10 ^-3 mm / year. Nitride multilayer materials have a cell viability factor> 65% in the cytotoxicity assay. 7

The monolayer oxynitride materials, according to the invention, are made of thin layers of ZrON, TiON and TiAION, with total thicknesses between 0.6 and 4 pm. Stoichiometry 9 the thin layers of ZrON, TiON and TiAION approach that of the ZrO2 layer (1.8 <(O + N) / Zr <2.2; 1.8 <(O + N) / Ti <2.2; 1.8 <(O + N) / (Ti + AI) <2.2) and with an O / N ratio in the ZrON, 11 TiON and TiAION layers between 1 and 4 and with an Al / Ti ratio in the layers of TiAION between

0.4 and 1. The monolayer materials are adherent to the substrate, the critical normal forces at the 13 scratch test being 16 ... 32 N. The monolayer materials have microdurities between 16 ... 20 GPa. The amount of ions released in corrosive solution 15 Ringer at 37 ° C is <45 pg / cm, and in corrosive Carter-Brugirard solution at 37 ° C is <80 pg / cm ² , falling (according to ISO 8044) in the class of perfectly stable resistance. The 17-layer materials have a corrosion rate <1x10 ^-3 mm / year. The monolayer oxynitrous materials show a cell viability factor> 75% in the cytotoxicity assay. 19

The multilayer materials of oxynitrides, according to the invention, are made of individual thin alternating layers, either of ZrON and TiON, or of ZrON and TiAION, with total thicknesses between 21 and 0.6 and 4 μm. The thicknesses of the thin layer pairs are between 5 and 400 pm, with the ratio of the thicknesses of the individual layers (ZrON) / (TiON) and (ZrON) / (TiAION) between 23 and 4. Stoichiometry of the alternating thin layers of ZrON, TiON and TiAION is the same as that of the corresponding monolayers of ZrON, TiON and TiAION, respectively. The multilayer materials 25 have high adhesion to the substrate, the normal forces critical to the scratch test being 30 .. .35 N. The multilayer materials have microdurities 27 between 22 ... 26 GPa. The amount of ions released in Ringer's corrosive solution at 37 ° C is <30 pg / cm ² , and in Carter-Brugirard's corrosive solution at 37 ° C it is <15 pg / cm ² , falling to 29 (according to ISO 8044) in the class perfectly stable resistance. Multilayer materials have a corrosion rate <1x10 ^-3 mm / year. Multilayer oxynitrous materials have a cell viability factor> 80% in the cytotoxicity assay.

The biocompatible biocompatible materials for covering 33 biomedical implants from shape memory alloys according to the invention have the following advantages:

- high adhesion to the substrate; 35

- high microhardness;

- mechanical and tribological properties stable over time; 37

- low roughness;

- low corrosion rate under the action of corrosive agents found in the human body;

- low amount of ions released in Ringer artificial saline and Carter-Brugirard artificial saliva 41;

- low wear coefficient. 43

The mono- and multilayer materials of nitrides and oxynitrides, according to the invention, are obtained by a method of physical vapor deposition (magnetron spraying, cathode arc, ion plating, activated evaporation) in a reactive plasma.

The following are 3 embodiments of the multilayer material according to the invention.

RO 123356 Β1

Example 1. The material consists of alternating layers of ZrN, with the ratio N / Zr = 0.82, and TiN with the ratio N / Ti = 1.08. The multilayer material has a total thickness of 0.6 μm, having a ZrN / TiN pair thickness of 20 nm, with an individual layer thickness (ZrN) / (TiN) thickness ratio of 1.1. The multilayer material has high adhesion to the substrate, the critical normal force at the scratch adhesion test being 52 N. The multilayer material has a microhardness of 32 GPa. The multilayer material has corrosion rates of approximately 0.5 x 10 ^-3 mm / year in Ringer's corrosive solution at 37 ° C, falling (according to ISO 8044) in the perfectly stable strength class. The amount of ions released in Ringer's corrosive solution is approximately 46 pg / cm ² .

The multilayer nitride material has a cell viability factor> 68% in the cytotoxicity test.

Example 2. The multilayer nitride material consists of alternating layers of ZrN, with the ratio N / Zr = 1.27, and TiAIN, with the ratio N / (Ti + AI) = 0.7 and with the ratio Al / Ti in the layer of 1.5 TiAIN. The multilayer material has a total thickness of 3.9 μm, having a thickness of a ZrN / TiAIN pair of 5.5 nm, with a thickness ratio of individual layers (ZrN) / (TiAIN) of 2.7. The multilayer material has high adhesion to the substrate, the critical normal force at the scratch adhesion test being 48 N. The multilayer material has a microhardness of 28.3 GPa. The nitride multilayer material has corrosion rates of approximately 0.4 x 10 ^-3 mm / year in Ringer's corrosive solution at 37 ° C, falling (according to ISO 8044) in the perfectly stable strength class. The amount of ions released in Ringer's corrosive solution is approximately 41 pg / cm ² . The monolayer oxynitrous material has a cell viability factor> 78% in the cytotoxicity assay.

Example 3. The multilayer material of oxynitrites consists of alternating layers of ZrON, with the ratio (O + N) / Zr = 1.61, and TiON, with the ratio (O + N) / Ti = 1.91 and with the ratio O / N in the 1.9 ZrON layer and in the 2.5 TiON layer. The multilayer material has a total thickness of 1.2 pm, having a thickness of a ZrON / TiON pair of 400 nm, with the thickness ratio of the individual layers (ZrON) / (TiON) of 3. The multilayer material (ZrON) / (TiON) is adherent to substrate, the critical normal force at the scratch test is 30 N and has a microhardness of 22 GPa. The multilayer material has a corrosion rate of approximately 0.2 x 10 ^-3 mm / year in Ringer's corrosive solution at 37 ° C, falling (according to ISO 8044) in the perfectly stable strength class. The amount of ions released in Ringer's corrosive solution is about 22 pg / cm ² . The multilayer oxynitrous material has a cell viability factor> 81% in the cytotoxicity assay.

The material of the TiNiNb alloy substrate has a microhardness of about 5.6 GPa and has a corrosion rate of about 7x10 ^-3 mm / year in Ringer's corrosive solution at 37 ° C, falling (according to ISO 8044) in the very strength class stable, and the amount of ions released in Ringer's solution is about 730 pg / cm ² .

Mono and multilayer materials are obtained in a reactive plasma containing atoms and ions of titanium, aluminum, zirconium and nitrogen, at pressures between 1x10 ^-3 and 5x10 ^-3 Pa, at the temperatures of the alloy on which the deposition is made between 3O ... 5O ° C, which does not cause structural changes, the deposition time being between 60 and 90 min.

Claims (4)

Revendicări1 1. Thin layer material, biocompatible, for coating alloys with NiTi and NiTiNb type 3 memory, in the form of a monolayer based on Zr and Ti oxynitrides or a multilayer based on nitride or oxynitride of Zr, Ti and Al, characterized in that it consists5 of alternating thin layers of ZrN and TiN or ZrN and TiAIN or ZrON and TiON or ZrON and TiAION, having the thicknesses of the pairs of thin layers between 5 and 400 nm and 7 the total thicknesses between 0.6 and 4 pm , a ratio of the thickness of the individual layers ZrN / TiN and ZrN / TiAIN between 0.25 and 4, respectively ZrON / TiON and ZrON / TiAION between 1 and 9 4, an Al / Ti ratio in the TiAIN and TiAION layers between 0.4 and 1 and an O / N ratio in the ZrO, TiON and TiAION layers between 1 and 4.11 Biocompatible thin layer material according to Claim 1, characterized in that it consists in the form of a multilayer of alternating thin layers of ZrN and TiN or 13 ZrN and TiAIN, has an amount of ions released in Ringer's corrosive solution <50 pg / cm ² , and in Carter-Brugirard corrosive solution <40 pg / cm ² , they have corrosion rates <0.5x10 ^-3 mm / year and15 have a cell viability factor> 65% in the cytotoxicity test. Biocompatible thin-film material according to Claim 1, characterized in that it consists in the form of a monolayer of ZrON, TiON and TiAION thin-film, has an amount of ions released in Ringer's corrosive solution <45 pg / cm ² , and in Carter-Brugirard corrosive solution <80 pg / cm ² , they have corrosion rates <1x10 ^-3 mm / year and have a cell viability factor> 75% in the cytotoxicity test. 21 Biocompatible thin layer material according to Claim 1, characterized in that it consists in the form of a multilayer of alternating thin layers of ZrON and TiON 23 or ZrON and TiAION, has an amount of ions released in Ringer's corrosive solution <25 pg / cm ² , and in Carter-Brugirard corrosive solution <15 pg / cm, they have corrosion rates 25 <1x10 ^-3 mm / year and have a cell viability factor> 80% in the cytotoxicity test.