EP3068451A1

EP3068451A1 - Implant with improved surface properties

Info

Publication number: EP3068451A1
Application number: EP14796766.5A
Authority: EP
Inventors: Arik Zucker; Stefano BUZZI; Armin W. MÄDER; Vincent MILLERET; Martin Ehrbar; Algirdas ZIOGAS
Original assignee: Qvanteq AG
Current assignee: Qvanteq AG
Priority date: 2013-11-14
Filing date: 2014-11-12
Publication date: 2016-09-21
Also published as: WO2015071324A1; CH708834A1; US20160346437A1

Abstract

An implant for vascular implantation in a body is provided with a surface which, in the implanted state, is provided for contact with the body or with a body fluid and which is at least for the most part hydrated. The surface is advantageously provided as a polished metal surface of a chromium-containing alloy. The vascular implant is used to regulate an adsorption of proteins on the surface of the implant, in respect of the type, quantity and/or shape of defined proteins, by a defined surface which is at least for the most part hydrated.

Description

Implant with improved surface properties

The present invention relates to an implant for vascular implantation in a body, in particular a vascular prosthesis z. In the form of a stent and a use of the implant for regulating a

Adsorption of proteins on a surface of the implant at the

Implantation.

Implants such. B. stents used in blood vessels, pose certain risks for the patient. Among other inflammatory reactions can occur and it can lead to a renewed stenosis in the blood vessels z. By thrombosis formation on the surface of the implant or by neointimal hyperplasia. For example, contaminants on the surface of the implant, such as may result from conventional handling and cleaning of the implant or transfer of the implant, can affect the body's response to the implant. Complications can be caused by the

Adsorption of proteins on the surface of the implant are triggered as soon as they come into contact with the body or with blood. The amount and type of adherent proteins determine the further biological reactions between the body and the implant. The adsorption of certain blood components is promoted or reduced and their effects activated or inhibited. This implant-body interaction determines the success or failure of the implant to grow into the body.

The successful ingrowth of an implant thus depends on the properties and the nature of the surface of the implant. Implants with various surface coatings are known from the prior art, wherein the individual coatings are intended to assist and influence the ingrowth of the implant in one way or another.

Further, from US 2008/0086198 A1 z. For example, a stent with a nanoporous surface layer is known to improve ingrowth of the stent and its reendothelialization and to reduce inflammation and intimal proliferation. In this case, the nanoporous surface layer may be provided with one or more therapeutic agents. Experimental results for stents with a controllable elution system disclosed in US 2008/0086198 A1 show in comparison to bare stents Metal surface (bare metal stents) a lower restenosis. In a stent with a simple metal surface, a chronic irritation of the tissue surrounding the stent is suspected.

EP 1254673 B1 shows a stent whose surface should be such that a recognition of the stent as a foreign body is minimized. For this purpose, the surface structure of the stent is intended to mimic the surface structure of the body's own cells. This is realized by spaced-apart microstructures on the stent surface which have an extension in the

Micrometerbereich have. It has been found that such stents exhibit improved immune tolerance than stents with a smooth or generally rough surface. Ingrowth of the stent can be further improved by using material with a positive surface charge in the range of 0.03 to 0.05 N / m. As a result, the adhesion of fibrinogen on the

Stent surface reduced. This should lead to a reduced inflammatory response and thus reduce the immune response.

Implants with coated surfaces or with surfaces which are provided with structures or a defined roughness are expensive to produce. Furthermore, such surfaces complicate the cleaning and

Keeping the surface clean during handling during manufacturing,

Storage and implantation process. In addition, such implants sometimes cause restenosis or others

Complications.

It is an object of the invention to provide an implant which reduces complications in the application of the implant in the body, in particular improves a desired ingrowth of the implant in the body and prevents restenosis, which allows easy manufacture and handling of the implant, a function of the implant in the Ensures long-term body and allows a high degree of purity of the implant surface. Furthermore, it is an object of the invention to adsorb proteins on the

Surface of the implant with respect to the compatibility of the implant and to improve a successful implantation.

This object is achieved by the invention by an implant according to claim 1 and a use of the implant according to claim 14. Advantageous embodiments and preferred examples are described in the dependent claims.

According to the invention, an implant for vascular implantation in a body is provided. The implant has a surface which is provided in an implanted state for contact with the body or a body fluid and which is hydrated at least for the most part. The surface thus has a hydration which covers at least the majority of the surface. Preferably, the surface is completely covered with the hydration. The invention includes vascular implants of any kind, in particular implants that come into contact with body fluids and are used in the field of fluid dynamics of the body. In particular, an implant with the features according to the present invention may advantageously be designed as a vascular prosthesis, such. Stents, grafts, heart valves, pacemaker elements, etc. The invention particularly relates to cardiovascular implants used in soft tissue of the body, such as stents. In contrast to bone implants such implants should not absorb or absorb the body fluid, such as blood. Stents are usually tubular and constructed from a plurality of webs, which together form a kind of grid. The surface of a stent is formed by the surface of the webs or of the grid.

First, the implant is in a first state in which there is little or no hydration of the surface. The surface is then subjected to a treatment for hydration so that the surface is at least largely hydrated in a second state in which the implant is inserted into the body or body lumen. The characteristic of the implant surface in the first state can be the characteristics of a

Starting material from which the implant is made, correspond. The first state may also be referred to as a state of a conventionally manufactured and

Implantation provided implant can be considered. The first state can thus be regarded as the initial state of the implant, in which the implant z. B. after molding or a first cleaning is present. Also, in the initial state, the implant may already be mounted in or on an insertion system.

Preferably, the implant surface is fully hydrated during implantation. This includes the inner and outer surfaces, but also the lateral surfaces, as with a stent through his

Grid shape are given. Hydration can be achieved by hydroxide groups attached to the surface to which

Water molecules are adsorbed. The hydration preferably comprises at least one water monolayer on the surface. Advantageously, more water molecules are bound to the water monolayer, so that a

Hydration layer is present with a greater thickness than in the water monolayer. It can also be several monolayers stacked on each other. The water monolayer is by hydrogen bonds (H-bridges) strongly to the

Hydroxide groups bound to the surface. Other water molecules can be bound by dipole-dipole bonds and / or by Van der Waals forces and / or H-bridges weaker to the water monolayer and thus form further molecule layers.

From the normal ambient atmosphere, surfaces can become contaminated by the substances contained therein, e.g.

Hydrocarbons, etc .. In the implant according to the invention, these contaminants should be kept as low as possible or even completely suppressed, on the hydrated surface itself, on the overlying water monolayer and possibly on the water monolayer located further water layers. Likewise should

Contamination within the aforementioned water layers can be reduced or even completely suppressed. A possible protection against such

Contamination provides e.g. a suitable inert wrapping or packaging. In order to maintain the hydration of the implant surface, handling and storage of the implant can take place, as described in applicant's co-pending patent application (application number CH 00048/12).

In a preferred embodiment, the metal surface for hydration may have a first surface charge in a first state and take a second state with a second surface charge having a lower positive surface charge or a higher negative surface charge compared to the first

Has surface charge. A bare metal surface with such a surface charge favors complete hydration of the surface. A surface with such a surface charge can have a positive effect on the surface even without at least approximate hydration Have ingrowth of the implant. The Applicant therefore reserves the right to make a separate patent application, the content of which

Properties of the implant surface in full to illustrate

Embodiments of the present invention are referred to.

Accordingly, the surface in the second state, in which the

Implant inserted into the body or a body lumen, overall a more negative surface charge than in the first state. Preferably, the second surface charge of the surface is negative. This can be done by the

Surface treatment can be realized even if the surface charge in the first state has a positive value.

The use of an implant according to the present invention is intended to regulate adsorption of proteins on the surface of the implant with respect to the type, amount and / or conformation of particular proteins through a defined surface that is at least largely hydrated. The defined surface may also have a defined surface charge and / or a defined predetermined composition of an oxide layer of the surface. The defined state becomes a desired one

Regulation of protein adsorption set. Accordingly, different defined states can be defined for different requirements of the protein adsorption, which are each achieved by a suitable surface treatment.

With an implant according to the present invention, implantation of the implant can change the amount of surface-adhering proteins and other elements, for example, reducing unwanted proteins and increasing the location of desired proteins. Neutrophils can be increasingly located on the implant surface, which secrete cathelicidin and are therefore responsible for a reduction of restenosis. The adsorption of platelets can be reduced. Thus, the risk of complications in the implantation of an implant is significantly reduced and the ingrowth of the implant is improved. Complication by breaking or chipping off coatings on the implant, as known in the art

locked out. Good results have been obtained with implants according to the invention in which the second surface charge is at least 10%, preferably 20% or more, more negative than the first surface charge. In the second state, a zeta potential value of the surface should be below the zeta potential value in the first state. At a pH of about 7.4, which corresponds to the pH of blood, a zeta potential value of less than -60 mV, in particular less than -70 mV, is advantageous. The zeta potential can z. B. serve to determine a defined state of the implant surface. The mentioned potential values refer to a determination method by means of electrokinetic analysis. When using other methods of determination, the values of potential values may need to be in accordance with the

Procedural standard to be adjusted.

Furthermore, the surface of the implant can be characterized by the isoelectric point on the surface. The isoelectric point is defined as the pH at which the surface charge is zero. According to the invention, the surface in the second state has an isoelectric point which is lower than in the first state of the surface. For example, the isoelectric point is below 5.0 for a hydrated metal surface. Thus, the isoelectric point can serve to determine a defined state of the surface.

The surface treatment for producing the hydrated implant surface may, for. B. be given by a cleaning treatment and subsequent storage in a treatment solution.

In particular, the implant surface can be stored in a neutral or slightly acidic aqueous solution, for example in a NaCl solution or WFI water (water for injection). For cleaning, the implant surface z. B. be subjected to a plasma treatment. For metallic bare

In particular, surfaces is an oxidation treatment with a

subsequent storage suitable in treatment solution. To produce a more negative surface charge, the implant surface of a

Surface charge reduction treatment, such as. B. a plasma treatment.

The implant is preferably made of metal or a

Metal alloy, in particular of a chromium-containing alloy, such as a cobalt chrome alloy or a platinum chromium alloy, or Nitinol. It can Also stainless steel can be used. Such materials and their

Properties are known for use with implants. Particularly preferably, the implant has a bare metal surface. There are thus no coating operations, as z. B. for medicines or the like is known, necessary. Also, the surface need not be aftertreated to produce a particular surface texture. Furthermore, a bare surface facilitates cleaning and thus enables highly pure

Implant surfaces. Particularly preferably, a hydrophilic surface is provided. The hydrophilicity can z. B. simultaneously with the

Surface charge reduction treatment or the cleaning treatment are generated or increased. Alternatively, a second surface charge and hydration may also be used with an implant

Medication coating be provided.

The metals or metal alloys used according to the invention for the vascular implants have metal surfaces which have an oxide layer in the outermost layer of their metal structure. The oxide layer is 2 - 3 nm thick and has oxides corresponding to the metal used. A

Cobalt chrome surface has e.g. a share of about 2 / 3Cr2O3 oxide. In an implant according to the present invention, the surface in the second state advantageously has an oxide layer which is opposite to the oxide layer in the first state, i. H. relative to the initial state, has altered amounts of oxides. It is also possible that the oxide layer in the second state has a changed thickness, preferably thicker, than in the first state. In the case of a cobalt chrome implant, the oxide layer of the surface in the second state relative to the first state may have an increased amount of chromium oxide and / or a reduced amount of cobalt oxide and nickel oxide. In the case of a nitinol implant, a reduced amount of nickel oxide or an elimination of nickel oxide can be achieved. Thus, a defined

Surface charge on the implant surface with a predetermined

Composition of different oxides are produced in the oxide layer. For a selective change of the oxide layer at a metal surface for

Implants are particularly suitable for chromium alloys. For a surface having hydration, chromium alloys containing at least 5% chromium are preferably used. Empirical studies have shown that, due to the high affinity of chromium for oxygen, such chromium alloys have an increased proportion of chromium oxide on the surface compared to

Chromium content of the alloy itself. The chromium oxide is therefore preferred externally attached to the alloy and in increased concentration. According to the invention, an implant is preferably used, which consists of a

chromium-containing alloy, wherein the surface has an oxide layer in which at least 30% of the oxide consists of chromium oxide, preferably of at least 50%. According to the invention, the chromium oxide reacts with the

Water molecules and results in chromium hydroxide, which is hydrated with at least one bound water monolayer. With such a proportion of hydrated chromium hydroxides can be ensured that the

Implant surface is at least largely hydrated.

The conformation of proteins adsorbed on an implant surface also influences the adhesion of neutrophils and

Platelets and thus on the ingrowth of an implant. Proteins are complex copolymers whose 3-dimensional structure is composed of several levels. The structure structure may include amino acid sequences, various helix and β-sheet structures, the shared structure of several polypeptides, and the like. A natural conformation is understood to be a conformation of the proteins which the proteins occupy, when no external influences affect and influence the 3-dimensional structure of the proteins. As an at least almost natural, or nature-like

Conformation is said to be a conformation where there are small changes in protein structure, but these changes have no or negligible influence on the function and effect of the protein. The proteins are different areas, eg. B. positively or negatively charged areas, hydrophilic and hydrophobic areas, which are exposed depending on the spatial organization of the proteins and can perform specific biological functions. By adsorption on one

Surface changes the protein conformation. Generally, a protein has z. For example, a highly denatured conformation is present on a hydrophobic surface, while a less denatured conformation exists on a hydrophilic surface. The hydrophilic components of the proteins in the natural conformation are usually located outside and the hydrophobic components are usually located inside and are accessible only by a strong conformational change for the hydrophobic surface. By measuring the ratio of α-helix and β-sheets or by measuring specific amino acids on the protein surface, information about protein conformation can be obtained. In the present invention was surprisingly found that z. As fibrinogen on an implant surface according to the invention can be settled at least almost in its natural, or natural-like conformation, as confirmed by the above observations. The effect of fibrinogen on an implant surface according to the invention can be improved, since fibrinogen mainly in a beneficial

Conformation is adsorbed. In contrast, fibrinogen is adsorbed on an implant surface in the initial state of a metal surface in a denatured state, thereby having a negative influence on the

Ingrowth of an implant takes place. In a denatured state, fibrinogen has an altered 3-dimensional structure and an altered spatial distribution of different fibrinogen regions than in a natural state. In other proteins, too, a natural conformation promotes positive implant ingrowth.

When implanted in a body lumen, the body's defense can detect the difference between natural and denatured protein, particularly fibrinogen, so that denatured protein is identified as a foreign body and a counter reaction is triggered. Fibrinogen and other proteins can be found in a natural conformation to a healthy

Einwachsverhalten of an implant to be beneficial while z. B. Fibrinogen in a denatured conformation is detrimental to the ingrowth. The sheer amount of fibrinogen is therefore less critical to ingrowth of the implant.

The Applicant therefore reserves the right to make a separate patent application on an implant for vascular implantation in a body having a surface intended to be in an implanted state for contact with the body or a body fluid, the surface comprising a layer of proteins, in particular of fibrinogen, in an at least almost natural, or

having a nature-like conformation. The location of proteins in an at least nature-like conformation is advantageously provided on a bare metal surface of the implant. Furthermore, the layer is advantageously provided on a hydrophilic surface of the implant. The remarks on the characteristics and the advantages of a position of proteins in an almost at least

natural or nature-like conformation of such

Patent application will be fully within the scope of the present invention Patent application was added to the present to the present

To complement and support the invention.

When using the vascular implant, the amount of adsorbed proteins can vary compared to the initial state of the implant surface in the defined second state of the surface. For example, the absolute amount of proteins adsorbed may be reduced and / or certain types of proteins may be increased and other types of proteins may be less adsorbed. Thus, the risk of unwanted

Deposits of proteins diminished. Thus, the nature of the adhered proteins can be regulated by generating a suitably defined second state with the hydration and, for example, different oxides in the oxide layer or different surface charge. By producing an implant with a hydrated surface, the adsorption of the proteins can be influenced. There may be less macroglobulin and / or apolipoprotein A adhered to the surface and more apolipoprotein E, kininogen and / or plasminogen adsorbed. In addition, the conformation of proteins on the surface can be regulated. For example, fibrinogen may correspond to its natural conformation on the

Implant surface are settled, as stated above. This preserves its natural activity and promotes the deposition of neutrophils.

Exemplary embodiments and experimental results for implants according to the invention are explained below with reference to the figures, which are not to be construed restrictively. From the figures manifesting

Features and relationships are to be considered individually and in any combination as belonging to the disclosure of the invention. In the figures show:

1 shows a schematic sequence of the ingrowth of a conventional bare metal stent (above) and of a bare metal stent according to the invention with an increased negative surface charge according to the invention (below),

2 shows a diagram of the chemical process during hydration of a metal surface with chromium oxide,

Fig. 3a Diagram of the amount of adsorbed proteins on an implant metal sample with a cobalt chromium surface with a first Surface charge and a second surface charge from a measurement by μ-BCA method,

Fig. 3b Diagram of the amount of adsorbed proteins on an implant metal sample with a cobalt chrome surface with a first

Surface charge and a second surface charge from a measurement using the qubit method,

4a-4g are diagrams of the protein adsorption of a

Implant metal specimens having a cobalt chrome surface with a first one

Surface charge and a second surface charge for the proteins

Plasminogen, kininogen, apolipoprotein E, apolipoprotein A, a2-macroglobulin, fibrinogen and albumin,

Fig. 5 is a diagram of a number of neutrophils

Sample surfaces having a first surface charge and a second surface charge in different environments,

Fig. 6 diagram of the relationship of a

Fibrinogen concentration on the adsorption of neutrophils,

Fig. 7 diagram of a number of neutrophils on

Sample surfaces with an untreated surface and a hydrated surface for different sample surfaces and

8 shows a diagram of a number of platelets

Sample surfaces with an untreated surface and a hydrated surface for different sample surfaces.

Various experiments have been performed and various methods of measurement used to investigate the significance of the improved ingrowth of a vascular implant according to the present invention. It was clearly established that an implant with an at least for the most part hydrated surface compared to a

Implant surface with little or no hydration, or a

Implant surface without a hydration treatment, favoring ingrowth of the implant without complications. As a vascular implant, a stent was used with a bare metal surface, as z. B. made in the prior art and is used as a vascular prosthesis. The outer surface of the stent is intended to rest against a vessel wall of a body. The surfaces of the stent come into contact with the blood in the vessel. Furthermore, metal samples were z. B. used in the form of discs for performing surface measurements. The metal samples consist of a metal or a metal alloy, as it is also used for a vascular implant, or the stent. Thus, the metal surfaces of the samples are equivalent to surfaces of stents intended for implantation. It is investigated cobalt chromium, platinum chromium and nitinol. Basically, other metals or metal alloys with

comparable properties can be used for an implant according to the invention.

The following metal samples were used in the measurements described below: A cobalt chrome alloy MP35N (ASTM F562) consisting of about 34 wt% cobalt, about 35 wt% nickel, about 20 wt% chromium, about 10 wt% molybdenum, and less than 1 wt% of titanium and iron and one

Cobalt chromium alloy L605 (ASTM F90) consisting of about 51 wt% cobalt, about 20 wt% chromium, about 15 wt% tungsten, about 10 wt% nickel, less than 3 wt% iron, about 1 .5 wt% Manganese and less than 1 wt% silicon.

The following measuring methods and measuring equipment were used: X-ray photoelectron spectroscopy (XPS measurement) with a Kratos Axis Nova instrument on 12 different samples and zeta potential measurement with a Surpass Electrokintetik Analyzer with variable pH on 2

different samples.

The investigated stents and the metal samples are initially in a first state with little or no hydration, the one

Initial state corresponds. The initial state is z. Example, in a stent, as it is used in a conventional manner for implantation. The stent is thus finished in the initial state and ready for implantation in the sense of the prior art. To create the second state with at least a majority of the surface hydrated, the stent and metal samples are surface treated. Such a surface treatment for generating the hydration may, for. B. be a bath in a previously mentioned solution. In addition, a surface treatment to change the surface charge can be done, for. Example, by an oxidation treatment in the form of a plasma treatment and / or a bath in a previously mentioned aqueous solution. The plasma treatment results in oxidation and removal of hydrocarbon. Different gases can be used for the plasma, as known from the prior art. For example, an oxygen plasma is used. The bath may have a predetermined pH, which is tailored to the material of the metal samples. For example, an alkaline solution is used. For example, to reduce surface charge on the surface, an argon plasma that is non-oxidizing may be used in combination with a bath in an aqueous NaCl solution that acts as an oxidizer. The treated surface has uniform surface properties with a second, lower surface charge and hydration in the sense of the invention.

In order to maintain the hydration of the implant surface, handling and storage of the implant can take place, as described in applicant's co-pending patent application (application number CH 00048/12). This application is fully incorporated into the disclosure of the invention, as it shows in what way stent surfaces with defined surface properties can be maintained until implantation. With the provision of a stent within a flow of a defined medium in a sheath, the second state of the

Implant surface are maintained.

The stent may be subjected to a surface treatment even if it is already inserted in or on an insertion system for introducing the stent into the body or a body lumen, or after

Treatment can be used in such a system. It is important to ensure that the surface charge of the second state is maintained.

FIGS. 1a to 1c show the process of ingrowth of a conventional bare-surface metal stent V in a first state (above) and a bare-surface metal stent 1 according to the invention in a second state with an increased negative surface charge (below). FIG. 1d shows for the stents 1 and V the ingrowth of the stents in a coronary artery of a pig after 30 days. In Fig. 1 a, the stent is placed at the site of implantation and the

Surfaces are exposed to blood. In the case of the conventional stent 1 '(FIG. 1 a, top), a deposition of proteins takes place first, which involves both the

Adherence, as well as preventing the functionality of neutrophils, called neutrophil inhibitors 2 (a ² -macroglobulin, apolipoprotein A). The stent 1 with increased negative surface charge (Fig. 1 a, bottom) are the

Neutrophil inhibitors are strongly reduced and at the same time deposit both proteins that prevent the adhesion of platelets (Kininogen high molecular weight - HMWK), as well as proteins that promote the adhesion of neutrophils on the stent surface (eg plasminogen, fibrinogen in natural or Accordingly, the stent V in the first state (FIG. 1 b, top) on the neutrophil inhibitors 2 is then mainly colonized by platelets 4, which are generally undesirable. In the case of the stent 1 with increased negative surface charge (FIG. 1 b, bottom), on the other hand, neutrophils 5 from the patient's blood are placed on the neutrophil promoters 3 and activated, while platelets are rejected. The activated neutrophils 5 but the protein cathelicidin (LL37) 6 on the stent surface, cf. Fig. 1 c below.

As a result, the process of ingrowth can be positively supported without the need for a drug coating on the metal surface

must be applied or a drug delivery is required. In stent V in the first state, cathelicidin was found only to a small extent. The studies have shown that the stent 1 in the second state accumulates two to three times more cathelicidin than the conventional stent.

FIG. 1 d shows for the stents 1 and 1 'the ingrowth of the stents in a coronary artery of a pig after 30 days. The stent 1 with a hydrated surface shows a uniform ingrowth behavior with a widely open inner lumen (see Fig. 1 d, bottom). However, the stent V in the initial state shows ingrowth with a re-narrowing of the passageway (see Fig. 1d, top). In summary, the surface of the stent 1 with a surface that is hydrated at least largely in relation to conventional stents supports and promotes those bioactive processes that lead to a healthy and desirable ingrowth of the stent 1.

Undesirable processes, on the other hand, are contained or prevented. FIG. 2 shows the states during hydration of an implant surface with chromium oxide in the outer oxide layer. On the left, the chromium oxide is shown in a state without hydration. The chromium atoms, bound by their high affinity for oxygen, oxygen atoms.

Starting from this state, the chromium oxide is converted into chromium hydroxide by chemisorption of water molecules, in which the hydroxy groups are bound by a strong bond to the surface (Figure 2, center). By water physisorption, another state (Figure 2, right) is obtained with a physisorbed water layer in which the water may be partially dissociated. The water molecules are through a

Hydrogen bond bound to the hydroxy groups. In this state, the implant surface has a water monolayer, as is preferably provided for the hydration according to the invention. On this water Monolage can, for. B. by a water bath, other water molecules

be attached and thus a thicker layer of water can be achieved. These other water molecules are weaker bound, such as van der Waals or dipole-dipole forces. The physisorption of water molecules can be achieved by a suitable pretreatment, for. As a cleaning and in particular by reducing the surface charge, be supported, so that an at least largely hydrated implant surface can be reliably prepared.

Experimental investigations of an oxide layer on a surface of MP35N and L605 samples have shown that in the initial state the oxide layer has a thickness of 2-3 nm. When determining MP35N samples with the Electrokinetic Analyzer (XPS measurement), the following was found. In a first MP35N sample in the initial state, the oxide layer consists essentially of about 66% Cr ₂ Os (Cr (III)) oxide, about 10% Co-oxide, about 10% Mo oxide, about 9% Ni Oxide, about 5% Ti oxide. A second MP35N sample was subjected to an oxidation treatment followed by storage in a neutral solution and thus is in a second state according to the

Invention. In the second sample, the MP35N oxide layer also has a thickness of 2 - 3 nm and is made of 75% Cr ₂ O (Cr (III)) oxide, about 7% Co oxide, about 8% Mo oxide, ca 7% Ni oxide and about 4% Ti oxide. When measuring the L605 samples, comparable results were obtained. Only molybdenum is substituted by tungsten and less nickel is measured, which is compensated by cobalt, as it corresponds to the different ratios of metals in the different alloys. It was a larger amount Chromium oxide and a smaller amount of cobalt and nickel oxide measured.

As a result, in the second state with an increased negative surface charge, the amount of chromium oxide is higher and the amount of cobalt oxide and nickel oxide is lower than in the first state. In addition, a hydration forms on the surface, the water molecules z. B. to the

Chromium ions bind, as previously explained.

As previously mentioned, by the type of surface treatment, ie z. B. cleaning by plasma treatment and wet storage in

Solutions, on the one hand the surface charge can be changed to a more negative value and on the other hand, the composition of the oxide layer can be influenced and thus regulated.

For the two metal samples of different cobalt chrome alloys used in the investigations, the zeta potential and the surface charge were determined. The zeta potential was measured at pH 7.4 in dilute KCl solution as it corresponds to the pH conditions in blood. In the second state after the surface treatment, the MP35N sample has a zeta potential of about -95 mV. For the L605 sample a zeta potential of -80mV is measured. This corresponds to a more negative surface charge for both samples after surface treatment. Both treated samples have an isoelectric point below 5.0. The zeta potential was determined by means of an electrokinetic analysis.

FIGS. 3a and 3b show results from the determination of the total amount of proteins adsorbed on the surfaces. FIG. 3 a shows the result of a μ-BCA measurement in which the effect of protein-copper chelate formation and the reduction of the copper with bicinchoninic acid (BCA) to a colored solution product for a fluorescence measurement is utilized. FIG. 3b shows the result of a qubit measurement in which the proteins adhering to the surface are desorbed and labeled with a marker

Fluorescence analysis be provided. Both methods show a significant reduction in protein adsorption.

Figure 3a shows the total adsorption of proteins for a metal sample with no or low hydration (first state, left bar) and for the metal sample with a hydrated surface (second state, right bar). In the first state, between 1 .2 and 1 .7 μg / cm ² Proteins adsorbed on the metal surface. In contrast, between 0.7 and 0.9 μg / cm ² proteins are adsorbed in the second state. In FIG. 3b, the

Total adsorption of proteins for a metal sample with little or no hydration (first state, left bar) and shown for the metal sample with a hydrated surface (second state, right bar). In the first state, between 36 and 40 arbitrary units of proteins are measured on the surface. In the second state, however, between 30 to 34 arbitrary units of proteins are measured.

FIGS. 4a to 4g are graphs of measurements of the protein adsorption of an implant having a cobalt chrome surface with little or no hydration (first state) and an at least predominantly hydrated (second state) surface for the proteins plasminogen (FIG. 4a), kininogen (FIG. 4b) , Apolipoprotein E (Figure 4c), apolipoprotein A (Figure 4d), a2-macroglobulin (Figure 4e), fibrinogen (Figure 4f), and albumin (Figure 4g). The metal samples correspond to the material of an implant according to the invention and have a bare cobalt chrome surface. In the first state, the surface is measured without further treatment steps, ie in the initial state. In the second state, the surface has been subjected to a hydration treatment as previously described and thus has an at least for the most part hydrated surface according to the invention. The zeta potential in the first state is approximately -55 mV and in the second state approximately -95 mV. The metal samples were incubated to measure protein adsorption in blood. For this purpose, the samples were placed in dishes with fresh blood and incubated for two hours at 37 ° C and static conditions. Subsequently, the samples were measured by the aforementioned method. The

Results in FIGS. 4a to 4g are shown such that the

Adsorption on the untreated surface is normalized to 100. Thus, the deviation therefrom present in a treated surface becomes clear.

In Figure 4a, the amount of plasminogen on the sample surface in the first state (left bar) and in the second state (right bar) is shown. The adsorption in the first state is normalized to 100 +/- 10. In the second state, however, a value of 400 +/- 150 is reached. In the second state, there is thus a significantly larger amount of plasminogen, which is responsible, inter alia, for the attachment of neutrophils. In Figure 4b, the amount of kininogen on the stent surface in the first state (left bar) and in the second state (right bar) is shown. The adsorption in the first state is normalized to 100 +/- 5. In the second state, however, a value of 300 +/- 80 is reached. FIG. 4c shows the amount of apolipoprotein E on the stent surface in the first state (left bar) and in the second state (right bar). The adsorption in the first state is normalized to 100 +/- 3. In the second state a value of 150 +/- 30 is reached. Kininogen and Apolipoprotein E are known to aggregate

Prevents platelets. Thus, the amount of platelets on an implanted stent surface can be regulated by increasing the proteins kininogen and apolipoprotein E on the surface.

In Figure 4d, the amount of apolipoprotein A is shown on the stent surface in the first state (left bar) and in the second state (right bar). The adsorption in the first state is normalized to 100 +/- 10. In the second state, however, only a value of 50 +/- 12 is reached. In FIG. 4e, the amount of α2-macroglobulin on the stent surface is shown in the first state (left bar) and in the second state (right bar). The adsorption in the first state is normalized to 100 +/- 2. In the second state, however, only a value of 80 +/- 3 is reached. In the second state, therefore, there is in each case a significantly smaller amount of apolipoprotein A and a2-macroglobulin.

Apolipoprotein A and a2-macroglobulin reduce the adsorption of neutrophils and inhibit the function of neutrophils. Apolipoprotein A also inhibits cathelicidin (LL-37), which promotes positive implant ingrowth.

FIG. 4f shows the amount of fibrinogen on the stent surface in the first state (left bar) and in the second state (right bar). The adsorption in the first state is normalized to 100 +/- 10. In the second state, however, only a value of 70 +/- 5 is reached. Fibrinogen can promote the adsorption of platelets and inhibit neutrophils. It is therefore advantageous to reduce the amount of fibrinogen on the implant surface.

In Figure 4g, the amount of albumin on the stent surface in the first state (left bar) and in the second state (right bar) is shown. The adsorption in the first state is normalized to 100 +/- 10. In the second state, however, a value of 1 15 +/- 15 is reached. In summary, it can be concluded that the stent surface in the second state has a hydrated surface in comparison to

Surface charge in the first state has fewer proteins that reduce the amount and function of neutrophils on the surface, and has more proteins that reduce aggregation of platelets. The results show that the metal surface in the second state is occupied by a smaller amount of proteins than in the first state. It is preferred

Platelet inhibitors, such as kininogen, and neutrophil promoters, such as

Plasminogen, adsorbed. Furthermore, fewer neutrophil inhibitors, such as. Apolipoprotein A and a2-macroglobulin settled on the surface. Therefore, neutrophils can rapidly attach to an implanted surface and promote successful ingrowth of the stent.

In a preferred procedure, a defined second surface charge and / or a defined predetermined composition of the oxide layer is formed on the implant surface by a surface charge reduction treatment and / or by an oxidation treatment, as above

described, which is tailored to a defined adsorption of predetermined amounts of various proteins on the surface and supports the hydration of the surface. The production of a defined surface can influence the adsorption of proteins, promote the adsorption of desired proteins and inhibit the adsorption of unwanted proteins. It is thus a selective

Protein adhesion on the metal surface. A stent with a hydrated surface according to the invention can reduce the amount of the implant

depositing proteins reduce fibrinogen, a2-macroglobulin and / or apolipoprotein A and increase the amount of proteins apolipoprotein E, kininogen and / or plasminogen.

These relationships are confirmed by measurements of the amount of neutrophils on a hydrated surface of a metal sample corresponding to a stent surface and such surface with little or no hydration. In Figure 5, cobalt chromium samples are incubated in fluids having different levels of proteins. In principle, proteins act as mediators for the colonization of neutrophils, whereby first proteins adhere to the surface and subsequently neutrophils. The left pair of bars shows a measurement in which the metal sample is exposed to regular human blood. It turns out that the sample without hydration (left bar), only about 8% the amount of neutrophils compared to a hydrated surface (right bar). The middle pair of bars in Figure 5 shows a measurement in which a metal sample was exposed to neutrophil fluid but does not contain proteins, as would normally be the case with a blood fluid. In the hydrated state (right bar), approximately 15% fewer neutrophils are deposited than in the first, untreated state (left bar). The right bar pair shows a measurement in which a metal sample is first placed in

Blood plasma was incubated. That is, it was first a deposition of proteins from blood and then an adsorption of neutrophils. In the hydrated state (right bar) approximately 20 times more neutrophils are deposited than in the state with no or low hydration (left bar). The measurements confirm that with a hydrated metal surface, compared to an untreated metal surface in the initial state, neutrophils are significantly more adsorbed if proteins are available that can react with the surface.

In FIG. 6, the example of the protein fibrinogen shows the influence of the presence of this protein on a metal surface state with and without

Hydration illustrated. Comparable measurements are also possible for other proteins. In the measurement series are each an untreated

Metal surface without hydration and a treated, hydrated

Surface exposed to a fluid with a constant proportion of albumin of 50 mg / ml and different proportions of fibrinogen and the amount of

adsorbed neutrophils measured. For the bar pairs for untreated (left) and treated (right) metal samples, the following proportions of fibrinogen were used from left to right: 3 mg / ml, 0.3 mg / ml and 0.03 mg / ml. In all three measurements 15 to 20 times more neutrophils are adsorbed on the hydrated metal surface than in the untreated ones

Metal surface. The measurements confirm that a hydrated surface, compared to the untreated surface, reduces the adsorption of fibrinogen and thus increases the number of adsorbed neutrophils that promote a positive ingrowth of an implant. Moreover, not only is the amount of fibrinogen available crucial, but also its conformation, as previously explained.

The measurements carried out prove the positive effect of an implant surface with a hydrated surface on the ingrowth of an implant after the implantation, as is shown in FIGS. vivo experiments is shown. Targeted adjustment of surface properties on the implant surface can be used to regulate the adsorption of proteins on the surface. An implant with at least a largely hydrated surface compared to conventionally used implants thus reduces the risk of restenosis or otherwise

Complications during implantation.

Figures 7 and 8 show the adsorption of neutrophils (Figure 7) and platelets (Figure 8) on several different metal surfaces. Measurements were made on the surface of an MP35N metal sample as described above and on pure metal surfaces. The

Pure metal surfaces include chromium, cobalt, nickel, titanium and molybdenum. These samples were prepared by placing glass slides with each

Pure metal (chromium, cobalt, nickel, titanium, molybdenum) by PVD (Physical Vapor Deposition) were coated, for example by

Vapor deposition. In each case a sample with no or only a slight hydration (left bar) and an at least largely hydrated sample (right bar) were incubated in regular human blood. Subsequently, the number of neutrophils on the surfaces (Figure 7) and the

Surface coverings by platelets (Figure 8) by means of

Measured by fluorescence microscopy.

As shown in Figure 7, in the low hydration MP35N sample, only about 22% of the amount of neutrophils is absorbed on the hydrated MP35N sample. A comparable result will be for a pure one

Received chromium metal sample. The bar pair for the pure cobalt metal sample shows that on a hydrated surface significantly more neutrophils are settled than on a hydrated chromium metal surface or MP35N surface. For the unhydrated cobalt metal sample (left), only about 23% of the amount of neutrophils is adsorbed onto the hydrated cobalt metal sample. The nickel, titanium and molybdenum samples show only a slight adsorption of neutrons. At the nickel metal sample are not at the

hydrated samples slightly more neutrophils than the hydrated sample. The titanium metal sample shows the lowest value of

Neutrophiladsorption. However, neutrophil adsorption is not

hydrated sample almost negligible. In the case of the molybdenum metal sample, about 100% more neutrophils are deposited in the non-hydrated samples than in the hydrated sample, but significantly less than in one at least for the most part hydrated surface of a chrome or

Cobalt metal sample. The measurements show that the hydration of an MP35N alloy, a chromium metal sample and a cobalt metal sample can significantly increase the adsorption of neutrophils and thus support a desired ingrowth behavior of the implant.

As shown in Figure 8, approximately four times more platelets are deposited on the MP35N sample with low hydration than on the

hydrated MP35N sample. A similar result is obtained for a pure chromium metal sample, with both chromium metal samples adsorbing slightly more platelets than the MP35N sample. In the

Cobalt metal sample is generally adsorbed to only a few platelets. In the non-hydrated cobalt metal sample (left) only about 100% more

Platelets as absorbed on the hydrated cobalt metal sample. In the samples of nickel, titanium and molybdenum, the hydrated samples show a negligible number of platelets, while in the non-hydrated samples the deposition of platelets is clearly detectable and in the

Range as with the MP35N and chrome sample. The measurements show for all samples a significantly reduced adsorption on a hydrated surface compared to a non-hydrated surface. The hydration of the

Surface therefore reduces the attachment of platelets regardless of the type of metal and can the ingrowth further positive

support.

In summary, it can be seen from FIG. 7 and from FIG. 8 that comparable values can be measured for the MP35N sample and the pure chromium sample, both with little or no hydration (left bar), and with at least a largely hydrated surface (right bar). It can be concluded that in the MP35N sample, chromium oxide in the oxide layer is primarily responsible for the adsorption of both the neutrophils and the platelets. Therefore, according to the invention, the use of chromium-containing alloys for the preparation of the implants with a hydrated surface is preferred. LIST OF REFERENCE NUMBERS

Implant, stent

Neutrophilinhibitoren

Neutrophilpromotoren

platelets

neutrophils

cathelicidin

Claims

claims

1 . An implant for vascular implantation in a body having a surface provided in an implanted state for contact with the body or a body fluid, characterized in that the

Surface at least for the most part has a hydration.

2. Implant according to claim 1, characterized in that the surface has a complete hydration.

3. Implant according to one of the preceding claims, characterized in that for hydration hydroxide groups are bonded to the surface to which water molecules are adsorbed.

4. Implant according to one of the preceding claims, characterized in that the hydration comprises at least one water monolayer on the surface.

5. Implant according to one of the preceding claims, characterized in that the hydration comprises a layer with physisorbed water.

6. Implant according to one of the preceding claims, characterized in that the surface is a bare metal surface.

7. Implant according to one of the preceding claims, characterized in that the implant consists of metal or a metal alloy, in particular of a chromium-containing alloy or nitinol.

8. Implant according to the preceding claim, characterized in that the alloy has at least 5% chromium.

9. Implant according to one of the preceding claims, characterized in that an oxide layer of the surface at least 30%

Has chromium oxide.

10. Implant according to one of the preceding claims, characterized in that at the surface a defined surface charge and / or a defined predetermined composition of the oxide layer is provided.

1 1. Implant according to the preceding claim, characterized in that the implant consists of a chromium-containing alloy and the surface has an oxide layer with at least 30% chromium oxide, preferably at least 50% and the chromium oxide is hydrated.

12. Implant according to one of the preceding claims, characterized in that the surface has a first surface charge in a first state and occupies a second state with a second surface charge by a surface treatment, wherein the second surface charge a lower positive surface charge or a higher negative surface charge in Compared to the first surface charge.

13. Implant according to one of the preceding claims, characterized in that the surface at a pH of about 7.4 has a zeta potential value of less than - 60 mV, in particular less than - 70 mV.

14. Implant according to the preceding claim, characterized in that the defined second surface charge and / or the defined predetermined composition of the oxide layer on a defined adsorption of predetermined amounts of various proteins on the

Hydration is tuned.

Use of an implant for vascular implantation according to any one of the preceding claims for regulating adsorption of proteins on the surface of the implant with respect to the type, amount and / or conformation of certain proteins through a defined surface which is at least largely hydrated.