RU2738307C1 - Method for producing thromboresistant medical products - Google Patents

Abstract

FIELD: medicine.

SUBSTANCE: invention refers to medicine, namely to developing thromboresistant medical products, and discloses a method for producing thromboresistant medical products made from titanium and based alloys. According to the invention, the articles are treated with a pulsed low-energy high-current wide-aperture electron beam of direct polarity, the article is under potential of the cathode. Thereafter, a-C:H:SiO_x film is applied with preliminary cleaning of article surface by ion flow in argon plasma, which provides removal of oxide compounds from surface and heating of surface to temperature of 170±20°C. Application of a-C:H:SiO_x film is carried out in a mixture of argon and polyphenylmethyl siloxane at pressure 0.1 Pa. Method can be used in medical industry.

EFFECT: method enables reducing the amount of adherent thrombocytes on the surface of medical devices, and also improves the biomedical properties of the articles, manifested in the absence of cytotoxicity to blood cells; applied a-C:H:SiO_x film also ensures imparting high wear resistance to articles due to high hardness and low friction coefficient.

4 cl, 1 dwg

Description

The invention relates to medicine, namely, to the creation of thromboresistant medical products made of titanium and its alloys, which are used in the medical industry and come into contact with blood, for example, mechanical heart valves, pumps for mechanical support of the heart, pacemakers, etc.

It is known that the interaction of implants with the biological environment of the body largely depends on their surface properties, which play a direct role in various post-implantation biological reactions, including the precipitation of various minerals, protein adsorption, adhesion and cell proliferation [1]. When applied to devices (mechanical pumps) and stents for the surgical treatment of coronary artery disease, redundancy of inflammatory cell-molecular reactions at the artificial surface / tissue interface increases the risk of thrombosis.

For the prevention and treatment of various thromboembolic diseases and their complications, for thrombosis and embolism of the great veins and arteries, vessels of the brain, eyes, during operations on the heart and blood vessels [2], heparin-based coatings are used, in particular, the protein-heparin coating "Bioline" [3], bioactive heparin coating “Carmeda” and biopassive heparin coating “Trillium” [4].

However, heparin-based coatings may be contraindicated in a certain group of patients with heparin-induced thrombocytopenia [5]. In addition, a serious disadvantage of using heparin is that it cannot coexist normally with agents that prevent restenosis (re-narrowing of an artery that has arisen in the place where stenosis was previously surgically removed) [6]. For example, if heparin is mixed with a polymer-coated antithrombotic agent, heparin, due to its hydrophilic nature, will interfere with the desired elution profile of the anti-restenotic agent. For example, a therapeutic agent is incorporated into a polymer coating matrix by treatment with a solvent. If the anticoagulant is also included in the polymer matrix, it will attract water in an uncontrolled manner. This can occur during coating formation or when the coated device is implanted and will adversely affect the stability or efficacy of the agent and / or interfere with the desired elution profile [6].

A known method of producing thromboresistant polymer material by radiation grafted copolymerization of a mixture of a hydrophilic monomer and an unsaturated biologically active compound at a weight ratio of a hydrophilic monomer unsaturated biologically active compound 1: 0.2 - 1: 1, where a mixture of acylated acrylic acid chloride is used as an unsaturated biologically active compound hirudin and ovomucoid acylated with acrylic acid chloride from duck egg protein at a mass ratio of 1: 0.8-1: 2 [7].

This method is applicable for products made of polymer. The problem of thromboresistance remains unresolved for metal medical devices.

A known method of reducing platelet adhesion on titanium materials and alloys [8], taken by us as a prototype. The method is carried out in the following sequence: 1. Electron-beam processing of the product using reverse polarity of 28 kV (the product is under the anode potential); 2. Electron-beam processing of direct polarity 17 kV (the product is at the anode potential); 3. Electron beam processing of direct polarity 25 kV (the product is at the anode potential); 4. Application of diamond-like carbon coating (DLC).

The disadvantage of this technical solution - the prototype is that the technological process is complicated by the number of operations performed to achieve the effect of thromboresistance. In addition, diamond-like carbon (DLC) is used to increase wear resistance, which is characterized by high internal stresses, which leads to a low adhesive strength of the coating and, accordingly, reduces the durability and service life of products.

The objective of the present invention is to create thromboresistant medical products made of titanium and its alloys.

The technical result is:

- a decrease in the number of adhered platelets on the surface of medical devices;

- improvement of medico-biological properties of products, manifested in the absence of cytotoxicity in relation to blood cells.

Another technical result is also giving the surface of products increased wear resistance due to high hardness and low coefficient of friction.

The specified technical result in the implementation of the invention - a method of obtaining thromboresistant medical products made of titanium and alloys based on it, is achieved by the fact that in the known method, including electron-beam treatment of the product under cathodic potential followed by the application of a biocompatible coating based on carbon, according to According to the invention, an aC: H: SiO _x film applied to the surface of the product is used as a coating.

, а длина связей С-С - 1,54

).Deposition of aC: H: SiO _x films are produced from organosilicon liquid polyphenylmethylsiloxane PFMS-2 / 5L. The obtained aC: H: SiO _x films on titanium articles have high compatibility with the human biological environment, have thrombotic resistance, and also have low internal stresses, compared to diamond-like carbon films (DLC), due to the presence of Si-C bonds, which are longer than bonds C-C (the length of the Si - C bonds is 1.89

, and the length of the C-C bonds is 1.54

).

It is advisable to apply the aC: H: SiO _x film to the surface of the article, preheated by an ion flow from an argon plasma to a temperature of 170 ± 20 ° C to ensure high mobility of adsorbed atoms and obtain a structure with desired properties.

In addition, the electron-beam processing of the surface of products is carried out using a pulsed wide-aperture low-energy high-current electron beam under the cathode potential with an energy density of 3-10 J / cm and the number of pulses 5-10 times.

For the convenience of biomedical research, we have selected a sample in the form of a plate with a size of 40 × 40 × 1 mm ³ made of VT6 titanium, which is widely used in medical practice. The technology of obtaining thromboresistant products was also carried out on other grades of titanium VT1-0, VT1-00, VT6S.

The method is implemented in several stages.

1. The sample is cleaned in an ultrasonic bath filled first with isopropyl alcohol, then with acetone and distilled water for 10 minutes in each liquid. After that, the samples are dried.

2. The samples are loaded into a vacuum chamber, where the surface of the sample is processed using a low-energy high-current electron beam with an energy density of 3-10 J / cm ² and a number of pulses 5-10 times in a low vacuum, a residual pressure of 10 ^-4 Pa.

3. The aC: H: SiO _x film is applied. Polyphenylmethylsiloxane was used as a plasma-forming precursor for the formation of aC: H: SiO _x films. Provided a residual pressure in the chamber of the order of 10 ^-2 Pa. Before film deposition, the surface of the substrates was cleaned with an ion flow in an argon plasma, which removed oxide compounds from the surface and heated the surface in order to ensure high mobility of adsorbed atoms. In this case, the argon pressure was 0.3 Pa, and a pulsed bipolar bias voltage was applied to the substrate holder with a negative pulse amplitude of 1000 ± 50 V, a pulse repetition rate of 100 kHz, and a duty cycle of 60%. The heating current was 45 ± 5 A, and the discharge current was 7 ± 0.5 A at a combustion voltage of 100 ± 10 V. The temperature of the products was controlled by a K-type thermocouple and was 170 ± 20 ° C. After that, the aC: H: SiO _x film was deposited in a mixture of argon and polyphenylmethylsiloxane at a pressure of 0.1 Pa. In this case, the discharge current was 5 ± 1 A at a combustion voltage of 140 ± 10 V, and a pulsed bipolar bias voltage was applied to the substrate holder with a negative pulse amplitude of 500 ± 50 V, a pulse repetition rate of 100 kHz, and a duty cycle of 60%. The amplitude of the bias applied to the substrate holder affects the change in mechanical and tribological properties. The optimal amplitude of the negative displacement pulse from the point of view of maximum wear resistance is 500 ± 50 V [9]. Study of platelet adhesion.

To study platelet adhesion of samples from the blood of a healthy adult donor, 50 ml of platelet-rich plasma was obtained by centrifugation and separation of blood cells. The resulting plasma was diluted with 0.9% sodium chloride solution in a 1: 1 ratio. Samples of the material were immersed in the obtained platelet solution and incubated at 37 ° C for 30 minutes. Then the samples were washed with distilled water to remove poorly adhered platelets. The platelets remaining on the surface were fixed in a 2% glutaraldehyde solution at room temperature for 1 hour and dried in a thermostat at 37 ° C. After that, the samples were covered with a 5 nm layer of chromium and the surface was examined by scanning electron microscopy. The area occupied by platelets was calculated using the ImageJ software. In addition, the morphology of adhered platelets was assessed, namely the severity of the formed pseudopodia and the adhesion area as a marker of the degree of thrombogenicity of the coatings.

FIG. Figure 1 shows images of adhered platelets on the surface of a VT6 titanium sample before (a) and after (b) deposition of aC: H: SiO _x films obtained by scanning electron microscopy (SEM). It is shown that after the implementation of the proposed method, the number of adhered platelets is significantly reduced. So, on samples (a) without the implementation of the proposed method in an area of 300 × 300 μm ^{2, the} area occupied by platelets is 80-85%.

After the implementation of the method in a similar area, the area occupied by platelets is reduced to 5-10%.

Cytotoxicity

An in vitro study of cytotoxicity upon direct 24-h contact with samples (titanium and titanium with a coated aC: H: SiO _x film) showed that the proportion of viable cells in the studied groups of samples is about 80%. According to the international standard ISO 10993-5-2009, this testifies in favor of the absence of cytotoxicity of the samples against human mononuclear leukocytes.

Thus, it has been shown that when implementing this method, it is possible to drastically reduce the adhesion of platelets to the surface of products compatible with the human biological environment, made of titanium and alloys based on titanium, which is very important for use in medicine. In addition, the deposited aC: H: SiO _x film provides the surface of products with increased wear resistance due to high hardness and low coefficient of friction [9].

Sources of information accepted for consideration

1. Ali N., Kousar Y., Okpalugo T. I., Singh V., Pease M., Ogwu A.A., Jackson M.J. / Human micro-vascular endothelial cell seeding on Cr-DLC thin films for mechanical heart valve applications // Thin solid films. - 2006. - V. 515. - No. 1. - P. 59-65.

2. Mashkovsky A.D. Medicines. M. Medicine. 1993. T. 2.S. 79-81.

3. Ponomarenko IV, Shipulin VM, Ogurkova ON, Suslova TE / Effects of application of the biocompatible coating of the extracorporeal contour "Bioline" in cardiac surgery patients // Circulatory pathology and cardiac surgery. - 2013. - No. 17 (2). - S. 51-56.

4. Sevastianov V.I., Bondarenko P.V., Nemets E.A. / Hemocompatible heparin-containing coating for treatment of auxiliary circulatory systems and blood oxygenation // Perspective materials. - 2009. - No. 4. - S. 58-64.

5. Dudarenko S.V., Yezhova O.A. / Heparin-induced thrombocytopenia // Emergency cardiology and cardiovascular risks. - 2018. - T. 2. - No. 1. - S. 252-257.

6. RU 2472529, 20.01.2013

7.RU 2556996 C1, 06.03.2014

8.US 2013/0230422 A1, 05.09.2013

9.RU 2718028 C1, March 30, 2020

Claims (4)

1. A method for producing thromboresistant medical devices made of titanium and alloys based on titanium, including electron-beam treatment of the article under cathodic potential, followed by the application of a biocompatible coating based on carbon, characterized in that aC: H: SiO _x is used as a coating film. 2. The method according to claim 1, characterized in that the aC: H: SiO _x film is deposited in a mixture of argon and polyphenylmethylsiloxane at a pressure of 0.1 Pa. 3. The method according to claim 1, characterized in that the application of the aC: H: SiO _x film is carried out on the surface of the article heated by the ion flow from the argon plasma to a temperature of 170 ± 20 ° C. 4. The method according to claim 1, characterized in that the electron-beam processing of the article is carried out using a pulsed low-energy high-current wide-aperture electron beam.

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