WO2012028305A1

WO2012028305A1 - Coating for medicinal implants and coated medicinal implants

Info

Publication number: WO2012028305A1
Application number: PCT/EP2011/004376
Authority: WO
Inventors: Peter Behrens; Hansjörg HAUSER; Henning Windhagen; Peter Müller
Original assignee: Helmholtz-Zentrum für Infektionsforschung GmbH; Medizinische Hochschule Hannover; Gottfried Wilhelm Leibniz Universität Hannover
Priority date: 2010-08-31
Filing date: 2011-08-31
Publication date: 2012-03-08
Also published as: DE102010036039A1

Abstract

The invention relates to coatings for medicinal implants and medicinal auxiliary agents. The invention relates, in particular, to coatings for medicinal implants and medicinal auxiliary agents, said coatings comprising layered double hydroxides (LDH) having a divalent metal cation and a trivalent metal cation and anions and optionally embedded water. The invention also relates to coated medicinal implants or medicinal auxiliary agents comprising the claimed coating on a base body. The invention further relates to a corresponding method for producing said type of coated medicinal implants or medicinal auxiliary agents.

Description

COATING FOR MEDICAL IMPLANTS AND COATED MEDICAL IMPLANTS

The present application relates to coatings for medical implants and medical devices. In particular, the present invention relates to coatings for medical implants and medical aids with layered double hydroxides (LDH) with a divalent metal cation and a trivalent metal cation and anions and possibly embedded water. Furthermore, the present application is directed to coated medical implants or medical aids comprising a coating according to the invention on a base body. Finally, the present application relates to corresponding methods for producing such coated medical implants or medical aids. State of the art

The limited durability and premature relaxation of implants, in particular endoprosthetic joint replacement, represent an unsolved problem, especially with regard to young patients or prosthesis replacement situations. In addition, the risk of infection during implantation and the regeneration of the bone tissue come.

Medical endoprostheses or implants or corresponding medical aids in a wide variety of applications are known in large numbers from the prior art. Thus, the term "implant" for the purposes of the present invention includes both endovascular prostheses, such as stents, but

CONFIRMATION COPY also used in osteosynthesis implants, such as fasteners for bone, such as screws, plates or nails, but also prostheses in the hard and soft tissue, often commonly referred to as endoprostheses, and surgical suture, intestinal staples, vascular clips and anchor elements for electrodes.

The use of magnesium materials including pure magnesium and magnesium alloys for medical implants and medical devices has been widely described in the art, e.g. EP 02 798 275.0. Among other things, these bioresorbable but also resistant materials replace pure metallic implant materials, as they were previously used for biomedical applications. Here are in particular the earlier and still used cobalt-chrome alloys, the stainless steel 316L, pure titanium but also called titanium alloys. For quite some time, there have been many efforts in the area of developing bioactive coating systems for metallic implant materials. These coating systems are intended primarily to prevent a possible corrosive attack on the metallic substrate and / or to improve the bioactivity of the implant surface. Bioactivity includes e.g. stimulation of bone growth, bone ingrowth into the implant and anti-infective activity. At the same time, however, these implants and devices must also demonstrate sufficient biocompatibility with the surrounding tissue. Another problem here is the already mentioned and actually frequently occurring problem of infections after implantation of corresponding medical implants or when using medical aids.

Implants as permanent implants are formed, for example, from titanium, titanium alloys or stainless steel compositions. Bioresorbable or biodegradable implants are nowadays often made of magnesium and magnesium alloys. By biodegradable or bioresorbable is meant that, by appropriate degradation processes in the living organism, the material of the implant is dissolved. The implant loses its mechanical integrity at a given time through this process until it is completely dissolved. The term "bioresorption" or "bioabsorption" encompasses the subsequent absorption or absorption of the degradation products by the living organism.

Recently, it has been described that magnesium as well as magnesium oxide can exhibit an antibacterial effect, e.g. in Koresey S.R., et al, Trans. JWRI, 2002, 31 (1) 55-61.

However, negative effects on the surrounding tissue are also known for magnesium or magnesium hydroxide. Thus, the use of metallic magnesium as an undesirable side effect in the degradation of a significant amount of hydrogen and it comes to alkalization. Such and other reactions cause adhesion of cells to be impossible.

The use of magnesium alloys has tried to minimize this unwanted evolution of hydrogen, but this has not been achieved hitherto.

It was found that magnesium allows new options for the production of implants, in particular of endoprostheses. For example, it has been shown that degrading magnesium alloys, eg LAE 422, have a proliferating effect on the bone, and this effect has also been demonstrated for magnesium degradation products such as Mg (OH) ₂ . The degradation product of magnesium, Mg (OH) ₂ , appears to have a positive effect on periimplant bone remodeling in the early phase of bone healing. The exact mechanism for this is not clear.

Various coatings for the protection of permanently resistant implants against corrosive attacks and to improve the bioactivity of the implant surface with respect to the stimulation of bone growth and the ingrowth of the bone substance into the implant have been proposed. These include various technical processes, such as coating with calcium phosphates by means of plasma spraying, the alkali treatment of titanium surfaces or the deposition of apatites from liquid phase. A combination of sputtering and immersion techniques to produce low-temperature, apatite-based bioactive coatings using metallic magnesium has recently been described, eg, Ebasco, S., et al, Acta Biomaterialia, 5, 2338-2347, 2009.

A special type of magnesium-containing oxides is the layered double hydroxides, hereinafter referred to as layered double hydroxides, LDH, referred. In this LDH is by incorporation of cations other than magnesium from simple magnesium hydroxide, a characteristic layer structure. The layers carry a positive charge by replacing the Mg ²⁺ ions with trivalent metal ions. For charge balancing are between the

Layers of anions and additional water molecules incorporated. Such LDHs occur as a mineral in nature, e.g. the hydrotalcite,

[Mg ₆ Al 2 (OH) ₁₆ ] [CO 3 .4H ₂ O], which can be considered a prototype for this class of compounds.

LDHs, such as hydrotalcites, are used in a variety of ways. A known field of use is e.g. the use of hydrotalcite as a drug against an acidified stomach. Other applications of hydrotalcite range from use as a filler, flame retardant, catalyst, storage material for pollutants to thixotropic agents for cosmetic products.

The use of LDHs as carriers for anionic compounds, including pharmaceutical agents, nucleotides and DNA molecules, is also described in the prior art. That is, the anions may also be complex in nature, eg, dyes, drugs, biopolymers such as nucleic acids, etc. and can usually be exchanged in aqueous solutions. Furthermore, the use of LDH as a non-viral vector for transfection is described. EP 1 882 722 discloses coating compositions which have both nanoparticles of metal oxide and nanoparticles and / or microparticles of inorganic layer fillers. Suitable fillers are called sepiolite, phyllosilicates and LDH. Preferably, these are modified so that covalent bonds are obtained, for example, due to a reaction with a modifier. In the example, phyllosilicates or sepiolites are treated with polysiloxanes to form corresponding covalent bonds between these two reactants via the hydroxyl groups of the fillers. On the other hand, no examples of LDH are described. The combination of nanoparticles of metal oxides and the modified inorganic fillers, in particular the modified sepiolite and phyllosilicates carried out in the examples, showed an antifouling activity. The fields of application of this coating composition with antifouling activity are accordingly to be used in antifouling coatings, such as boat paints. Furthermore, the use of such coating compositions in biomedical areas are mentioned. For this, however, no examples are shown.

The "thermodynamic" solubility of LDHs with various cations and anions has been extensively studied, showing that the solubility product depends on the nature of the trivalent cations and, to a greater extent, on the type of anions.

There is a need to improve the osteointegration of implants and increase the biocompatibility of the implants. At the same time, the risk of infection should be kept as low as possible. In addition to an improved bioactivity and high biocompatibility, the implants preferably have also improved antimicrobial, especially antibacterial properties.

Brief description of the invention

The present invention relates to a coating for medical implants and medical aids, this coating Layered Double Hydroxides (LDH) - also called layered double hydroxides - has. These LDHs are in particular those of the general formula (I)

[M ^M _1-x M ^m _x (OH) 2] ^{x +} (A ⁿ -) _{x / n} · mH ₂ 0 (I) wherein M is ^M is a divalent metal cation, M ^m represents a trivalent metal cation, and A is an anion, x is a rational number> 0 and <1, in particular a number between 0.15 and 0.4, such as between 0.2 and 0.33, n is an integer between 1 and 4, in particular 1, 2 or 3, m is a positive integer including 0.

In a preferred embodiment, the LDHs are those in which the divalent metal cation is Mg ²⁺ . Most preferably, the LDH is hydrotalcite.

In a further preferred embodiment, the naturally occurring anions in the LDH are at least partially replaced by foreign ions, such as anionic pharmaceutical agents, biomolecules, nucleic acids for coding genes and as immune effectors, anti-infective agents and osteosynthesis-inducing substances.

In a further aspect, a coated medical implant or coated medical device comprising a coating according to the invention is provided on a base body. The basic body can be a permanent implant, for example of titanium or titanium alloys, or a biodegradable material, such as one of magnesium materials. The Medical implants according to the invention are in particular endoprostheses, such as implants in the bone cartilage area, these typically being permanent implants. Finally, a method is provided for producing such medical implants or medical devices coated according to the invention, comprising the step of coating them with a coating according to the invention containing LDH. The coatings according to the invention, ie the LDH-containing coatings, optionally additionally containing further foreign ions, are distinguished by improved biocompatibility combined with good bioactivity both with regard to anti-infective agents and the stimulation of bone growth and the integration of the implant into the surrounding tissue ,

Brief description of the illustrations

Figure 1 shows the antibacterial properties of various types of magnesium hydroxide. Shown is the inhibition of the growth of bacteria, here pseudomonas, in the presence of various magnesium hydroxides. As a positive control (C) no coating was taken, ie this value corresponds to 100% growth of the bacterium. For the 100% efficacy value, the antibiotic ciprofloxacin (CFX) was used (D). (A) shows the use of a coating with the LDH Mg ₄ Al ₂ (OH) ₂ / (NO ₃ ) ² ·

6H ₂ 0. (B) shows the antibacterial effect of Mg (OH) ₂ . Shown are the values for 0 hours or 3 hours.

FIG. 2 shows the results for investigating the biocompatibility of magnesium hydroxides. In the upper row, the coated titanium plates are shown. In the middle row microscopic images of the cells are shown. The black areas indicate precipitates and clumps by Zelldebris etc. In the lower row the classification with regard to the biocompatibility of the respective coating is shown. (+) means proliferating, spreading cells, (-) means rounded cells with lower cell density.

FIG. 3 shows the degradation of magnesium and magnesium alloys and the resulting development of gas bubbles as well as the influence thereof on mammalian cells on the implant surface. The left figure shows the foaming of metallic magnesium under cell culture conditions on an agar mass. The right panel shows the percentage of live cells, in this case NIH3T3 fibroblasts, in cell culture plates in the presence and absence of magnesium

FIG. 4 shows the release of CFX from LDH. The results are shown using 10 mg / ml, 1 mg / ml and 0.1 mg / ml CFX, respectively.

FIG. 5 shows the biocompatibility and antibacterial action of coating systems according to the invention and implants according to the invention in an animal model. It can clearly be seen that implants, in the present case titanium discs, which were coated with an LDH-containing suspension containing ciprofloxacin and additionally were infected with luminescent pseudomades, implanted in the mouse show a good biocompatibility and an efficient antibacterial effect. Clearly, a disappearance of the bacterial luminescence on the antibiotic-containing LDH coatings can be recognized, while in the control, which consists solely of uncoated titanium discs, the fluorescence of the bacteria can be recognized even after four hours.

Detailed description of the invention

The present invention relates to a coating for medical implant te and medical aids. This coating has double hydroxides known as Layered Double Hydroxides (LDH). In the following, the usual name LDH is used. These LDH present in the coating are, in particular, those of the general formula (I)

[M _"1-x M ^III _x (OH) _2] ^{x +} (A ^n") _{x / n} · mH ₂ 0 (I) wherein M "is a divalent metal cation, M ^m represents a trivalent metal cation, and A is an anion, x is a rational number> 0 and <1, in particular a number between 0.15 and 0.4, such as between 0.2 and 0.33, n is an integer between 1 and 4, in particular 1, 2 or 3, m is a positive integer including 0.

It was found that coatings containing LDH allow an improvement of the osteointegration of implants. More specifically, the coatings of the invention showed excellent biocompatibility with simultaneously antibacterial properties. Furthermore, those LDHs in which magnesium ions are present allow the integration of the implant into the bone by allowing the magnesium ions present and released from the LDH to exhibit both proliferation-inducing and differentiating effects on the corresponding cells in vivo.

That is, the quality of the implant-bone interface and the longevity of the composite can be improved with the coatings according to the invention. By coating the implant surface with LDH, in particular LDH with magnesium compounds, an improvement of the contact between implant and bone is achieved, and due to the bone profliferative effect of magnesium, a correspondingly improved integration of the implant is achieved. At the same time the mechanical properties are improved due to the improved integration. Problems such as may occur due to loosening of the implant are thus avoided. The coating according to the invention is in particular one which has no further fillers, such as layered silicates or sepiolite, a further silicate form. In particular, it is preferred that the coating itself contains no metal oxides. The coatings according to the invention are distinguished by the fact that, in addition to an antibacterial effect, they also avoid the quality of the implant bone interface and thus the problems of loosening the implant in the body. In particular, it is preferred that they thereby even improve the contact between implant and bone, by demonstrating bone-proliferative action and thus contributing to the improved integration of the implant.

The coating according to the invention allows the coating of smooth and structured surfaces. Depending on the implant, the LDH present in the coating can be selected so that osteoproliferation is promoted or, on the contrary, the osteogenesis is suppressed. This may e.g. be desired if the implants are stents or other implants placed in vessels. Accordingly, the foreign ions contained in the LDH can also be those which promote angiogenesis or counteract restenosis. Furthermore, the LDHs in the coatings of the present invention may be selected to provide the desired anti-infective effect, adhesion and biocompatibility. Finally, the coating according to the invention containing LDH can be chosen such that they allow a delay in the degradation of the main body. Thus, the coating may be one that degrades over an extended period of time while the body, e.g. made of a magnesium material, even then degraded faster.

Depending on the implant and the area of application of the implant, the LDHs used and the foreign ions present in the LDHs may be selected. That is, a known property of the LDH can be advantageously exploited. LDH show a delayed release of stored ions. This makes it possible to generate the stored ions and the associated effect over a long period of time. In contrast to Mg (OH) 2, Mg ²⁺ ions are secreted into the environment so that biocompatibility can be increased while maintaining antimicrobial and bone and tissue growth promoting properties, thus coatings with LDH according to the present invention superior to simple Mg (OH) 2-containing coatings.

Also, the stored foreign ions including the biologically active compounds can be released by the LDH much more controlled and regulated to the environment. In this case, the release can be controlled by appropriate selection of the LDH and the embedded ions, through the use of LDH is thus a simple control and control of the release of stored ions possible.

In a preferred embodiment, the LDHs present in the coating are those where M ^{M is} a divalent alkaline earth or transition metal ion, in particular Mg ²⁺ , Co ²⁺ , Fe ²⁺ , Cr ²⁺ , Mn ²⁺ , Zn ²⁺ . Further preferably, the M ^{m is} a trivalent main group or transition metal ion, in particular Al ³⁺ , Cr ³⁺ , Fe ³⁺ , Gr ³⁺ , Mn ³⁺ .

In preferred embodiments, the aions A ^{n "are} selected from CT, Pr ^" , E ^" , NO ₃ ^' , CO ₃ ^2" , SO ₄ ^{2 "} , HPO ₄ ^2' , OH ^" .

The anions in the LDHs may be replaced by other more complex anionic foreign ions. Such include, in particular, pharmaceutical active substances, biomolecules, nucleic acids for encoding genes as immunofector, anti-infective agents and osteosynthesis-inducing substances. These anions, which at least partially replace the naturally occurring anions in the LDHs, are preferably selected from: antibiotics, pharmaceutical active substances, in particular those with antimicrobial properties and growth-promoting properties for bones and tissue, biomolecules with growth-promoting Properties for the bone or tissue, etc.

Thus, with the help of LDH, foreign molecules that are present as anions or cations in the LDH can be introduced into the tissue via the coating in order to achieve the desired effects there. Such desired effects may be pharmaceutical effects, but also protective effects, such as antimicrobial, e.g. antibacterial effect. In particular, the inserted ions are organic ions which promote bone formation, such as growth factors, etc., or antibiotics for the prophylaxis of infections. Usually this introduction of these anions or the exchange of the anions during the synthesis or by a subsequent ion exchange takes place.

The literature describes various methods for introducing such materials into LDH, e.g. in Xu Z. P. and Lu G. Q., Pure Appl. Chem.

78 (9), 1771-1779, 2006.

Preferably, the ratio of M ^{n to} M ^is between 4: 1 to 2: 1, such as 4: 1, 3: 1 or 2: 1.

The coating is preferably one in which the LDHs are those of the general formula (II), (II) or (IV)

[Mg6M ^III ₂ (OH) _16] ²⁺ [A ⁿ -o, ₂ 5 / n · 4H ₂ O] ^{2 "(II)} or

[Mg ₄ M " ¹ ₂ (OH) ₁ 2] ²⁺ [A ⁿ -o, 33 / n * 4H ₂ O] ^2" (III) or [Mg ₈ M ^IM 2 (OH) 2 O] ²⁺ [A ⁿ -o, 2 / n ^* 4H ₂ O] ^{2 "} (IV) In a particularly preferred embodiment, the LDH are hydrotalcites, in particular hydrotalcites of the formula Mg ₆ Al ₂ (OH) ₁₆ A · 4 H ₂ O, where A is selected from C0 ₃ ^{2 "} , S0 ₄ ^2" , or 2N0 ₃ ^" .

These hydrotalcites have the additional advantage that the Mg ²⁺ cations present in these hydrotalcites have a promoting effect on bone formation and bone growth and thus promote osteointegration of implants with a corresponding coating according to the invention while at the same time reducing the risk of infections.

In another aspect, the present invention is directed to coated medical implants or medical devices comprising a coating of the invention and a body.

The main body can be designed as a permanent implant. Alternatively, the base body may also be one which consists of or comprises biodegradable material. The permanent implant is especially one selected from titanium or titanium alloys or from steel, in particular stainless steel. The person skilled in the corresponding materials are known.

Alternatively, the main body of the implant may also comprise biodegradable material. Such biodegradable materials are especially those of magnesium materials, as known in the art. Such magnesium materials may consist of magnesium or magnesium alloys. The skilled worker is familiar with suitable materials, in particular magnesium materials, which are biodegradable and bioabsorbable in the body. Furthermore, a plastic can be used as the main body. By coating corresponding plastic base body, which are suitable as an implant, in particular permanent implant, the biocompatibility of these plastics and the integration of these implants can be significantly improved. Alternatively, the coating composition itself may contain plastics. The person skilled in suitable plastic coatings are known. By adding the LDH according to the invention, it is possible to improve the integration and biocompatibility of plastic coating implants or other medical aids.

The coating according to the invention allows improved anchoring of the implants in the tissue or bone. By the osteo-activating function of the coating and an associated antibacterial effect, a possible inflammatory reaction can be suppressed. At the same time, the coating of the coated implant allows improved integration of the permanent implant into the tissue or into the bone. The medical implants coated according to the invention thus exhibit improved bioactivity of the implant surface, improved biocompatibility with the surrounding tissue and improved protection against infections.

In a preferred embodiment, the medical implants or medical aids are those implants used in medicine, in particular in osteosynthesis, in particular fastening elements for bones, such as screws, plates or nails, surgical sutures, intestinal staples, vascular clips, but also Prostheses, in particular endoprostheses in the field of hard and soft tissues. The coated medical implants according to the invention are preferably endoprostheses, such as implants in the bone-cartilage area, in particular artificial joints or parts of artificial joints. In a preferred embodiment, an intermediate layer is arranged between the coating and the main body. This mediator layer is intended to improve the wetting behavior and the adhesion of the coating on the base body. Typical mediator layers are in particular biocompatible metallic or metalloid systems based on titanium as well as magnesium-containing alloys. Examples include Ti, T1O2, TiN and TiC but also magnesium-containing alloys such as AZ31, AZ91, AM60 and AM50. The

Layer thickness of such mediator layers is e.g. in the range of 0.5 pm to 3 pm. The mediator layers may be graded, i. With permanent implants made of titanium or titanium alloys, these layers have a higher titanium content in the direction of the base body, while this proportion decreases in the direction of the coating. The amount of magnesium added may increase in the direction of coating with magnesium-containing LDH. The coating itself may be applied to the base body with a coating thickness of 1 μm to 100 μm or more. The LDHs are usually present in the form of layers and cavities. They are e.g. as nanoparticles, e.g. with particle sizes between 40 to 150 nm. The application of the coating and optionally the mediator layer can be carried out according to known methods. Common methods include spraying, dipping, drying.

In a further aspect, the present invention is thus directed to a method for producing the coated medical implant or medical aids according to the invention, comprising the step of coating, the medical implant or the medical aid with a coating according to the invention. The person skilled in the art knows the corresponding methods for applying the coating to the base body of the medical implant or medical aid. Possibly. becomes before applying the coating according to the invention, an intermediate layer is applied to the base body.

The advantageous properties of the coating according to the invention are explained below with the aid of examples.

Examples

example 1

Antibacterial properties of LDH

This example serves to illustrate the antibacterial properties of LDH as a component of the coatings according to the invention. To this end, 96-well cell culture plates (Nunc) were filled with 300 μl of appropriate solutions and coated by drying at room temperature. The holes were coated with aqueous solutions of 3.5 g / l magnesium hydroxide. Ciprofloxacin was used as a control with 1 mg / ml dissolved in H2O.

As magnesium hydroxide compounds, the following were used: a) Mg ₄ Al ₂ (OH) ₁₂ / (NO ₃ ) ² .6H ₂ O and b) Mg (OH) ₂ . The controls used were c) no coating, d) use of ciprofloxacin. As can be seen from the results for the coatings with the LDH used (a),

Mg (OH) ₂ (b) and the antibiotic (d) can recognize all have an antibacterial effect, (e) is without coating. The results show the results after 0 and 3 hours, respectively. For this purpose, 50 μl of luminescence-labeled pseudomonas were inoculated per hole at time 0 (5 μl of a fresh Pseudomonas aeruginosa, PA01 CTX: lux culture in LB medium adjusted to an OD 600 of 0.2 and 45 μl LB medium.) The bacteria were analyzed by luminescence in an imager (IVIS-200, Xenogen, Alameda, USA) after inoculation (0 hourly value) and after 3 hours of incubation at 37 ° C (3 hourly value). Example 2

Compatibility of LDH with cultured mammalian cells

Murine NIH3T3 fibroblasts were seeded in DMEM medium (Invitrogen) with 10% fetal calf serum (FCS) on appropriately coated titanium slides in 24-well cell culture plates and cultured under standard conditions at 37 ° C under humid atmosphere and 5% CO2 for two days. Biocompatibility was qualitatively assessed by microscopic observation from the attachment, propagation and proliferation of the cells. Here, (+) proliferating spreading cells and (-) rounded cells with low cell density.

The titanium flakes were previously coated with an aqueous solution of 1 ml each containing 3.5 g / l of magnesium hydroxide by drying at room temperature. The following approaches were carried out: Control:

Titanium without coating

LDH1) Mg ₄ Al ₂ (OH) ₁₂ / (NO ₃₎ ₂

LDH2) Mg ₄ Al ₂ (OH) ₁₂ / S0 ₄

LDH3) Mg ₄ Al ₂ (OH) ₁₂ / C0 ₃

and Mg (OH) ₂ .

As can be clearly seen from FIG. 2, the control without coating but also the LDH coated titanium platelets show good biocompatibility. there are proliferating, spreading cells to observe. Cell debris and death cells are hardly recognizable. The cell density is high. In contrast, the sample with MgOH ₂ coated titanium flakes. Here are the only rounded cells with low cell density can be seen. Furthermore, deposits (black spots) can be seen, the z. B. clumps and precipitates from Zelldebris etc. represent. From this experiment it is clear that, in contrast to the use of magnesium hydroxide as such, the LDH according to the invention show good compatibility with cells. Example 3

Degradation of magnesium and magnesium alloys and their influence on mammalian cells

In the following, it is shown that metallic magnesium does not meet the requirements for biocompatibility. For this purpose, a metallic magnesium cylinder (5 mm high and 5 mm diameter, 99.9% magnesium) was incubated in an agar layer under cell culture conditions (37 ° C., humid atmosphere, 5% CO ₂ ) for 24 hours on an agar layer. The cylinder was expelled from the agar matrix by gas formation, see Figure 3 left. Similar extrusion effects were observed with magnesium hydrate implants in animal experiments. The right panel shows the result of culturing murine NIH3T3 fibroblasts in 12-well cell culture plates. In the control, the percentage of living cells was almost 100%. In contrast, in the presence of a magnesium cylinder under the same conditions, no live cells were left after 1 day of incubation.

This experiment shows that metallic magnesium is not suitable as a coating material or as an implant because its biocompatibility with respect to the surrounding tissue is not given. Example 4

Release of ciproflxacin

An LDH suspension with the composition Mg ₄ Al 2 (OH) 2 / SO ₄ * 6H 2 O (3.5 g / l) as 1 ml aqueous solution was treated with the antibiotic ciprofloxacin (1 mg / ml) and placed in a 24-well Place the cell culture plate on a 9 mm diameter round glass slide and dry at room temperature for 2 days. The coated glass slides were placed in a new 24-hole plate PBS (137 mM NaCl, 2.7 mM KCl and 12 mM phosphate (HPO ₄ ^{2 "} and H ₂ PO ₄ ^~ ), pH 7.4) was overlaid with a phosphate-buffered solution, the solution being dissolved after 1, 2, 4 The ciprofloxacin concentration in the supernatant was determined with a nanodrop spectrometer at a wavelength of 272 nm The graph shows the concentration of ciprofloxacin in the supernatants as a function of time For comparison, ciprofloxacin alone in water (1 g / l) used ₂ 0 as shown in Fig. 4 as a control H, showed the LDH corresponding to the LDH2 of example 2, a delayed release of ciprofloxacin without an initial strong release (burst). This release was over a period In contrast, ciprofloxacin (CFX) alone, where the release rapidly decreased after an initial burst, was evident after only 4 hours outside of DHL containing CFX. After 2 days, detectable amounts of CFX are released by the CFH-added LDH, whereas for the CFX alone the release was no longer possible. Example 5

Biocompatibility and other antibacterial effects of LDHs in animal model Titanium discs 4 to 6 mm in diameter were suspended in deionized water using a suspension of 3.5 g / l LDH (Mg ₄ Al ₂ (OH) i ₂ / (S0 ₄ ) ₂ and ciprofloxacin) coated and subcutaneously implanted in a mouse (implants 1 and 3 as marked in Figure 5). As a comparison served an untreated titanium disc (marked with 2). The implants were additionally infected with luminescent pseudomadena (P. aeroginosa). The luminescence was recorded in an IVIS lean immediately after implantation (0 hours) and 4 hours later (4 hours). Shown are the results in false colors. The result shows a good compatibility and an efficient antibacterial effect, due to the disappearance of the bacterial luminescence on the antibiotics loaded LDH coating is occupied. In contrast, the comparison disc 2 shows luminescence.

Claims

claims

1. Coating for medical implants and medical aids comprising layered double hydroxides (LDH), in particular the general formula (I)

[M ⁿ _1-x M ^m _x (OH) 2] ^{x +} (A ⁿ -) _{x / n} · ^m H ₂ O (I) where M "represents a divalent metal cation, M ^{m represents} a trivalent metal cation and A represents an anion x is a rational number> 0 and <1, in particular a number between 0.15 and 0.4, such as between 0.2 and 0.33, n is an integer between 1 and 4, in particular 1, 2 or 3, m is a positive integer including 0.

2. Coating according to claim 1, wherein M "is a divalent alkaline earth or transition metal ion, in particular Mg ²⁺ , Co ²⁺ , Fe ²⁺ , Ca ²⁺ , Mn ²⁺ or Zn ²⁺ .

3. Coating composition according to claim 1, wherein M ^{m is} a trivalent main group or transition metal ion, in particular Al ³⁺ , Cr ³⁺ , Fe ³⁺ ,

Ga ³⁺ , Mn ³⁺ .

4. Coating according to one of claims 1 to 3, wherein A ^{n "is} selected from Cl ^" , Bf, Γ, N0 ₃ ^" , C0 ₃ ^2" , S0 ₄ ^{2 "} , HPO4 ^2" , OH ^" .

5. Coating according to one of the preceding claims, wherein the Me "in the LDH is Mg ²⁺ , in particular one of the general formula (II), (II) or (IV):

[Mg ₆ M ^m ₂ (OH) ₁₆ ] ⁺ [A ⁿ -o, ₂₅ / n · 4H ₂ O] ^{2 "} (II)

or

[Mg 4 M ^m ₂ (OH) ₁₂ ] ²⁺ [A ⁿ -o, 33 / n * 4H ₂ O] ^{2 "} (III) or

[Mg ₈ M ^lll ₂ (OH) ₂ o] ²⁺ [A ⁿ -o, _{2 / n} x 4H ₂ O] ^{2 "} (IV)

6. Coating according to one of the preceding claims, wherein this has a hydrotalcite of the formula Mg ₆ Al ₂ (OH) i ₆ A · 4H ₂ O, wherein A is selected from CO ₃ ^{2 "} , SO ₄ ^2" , 2NO ₃ ^" .

7. Coating according to one of the preceding claims, characterized in that the anions A or M ^{m are} at least partially replaced, in particular that the anions are at least partially replaced by pharmaceutical agents, biomolecules, nucleic acids for the coding of genes and as immune effectors, anti-infective agents or osteosynthesis inducing substances.

8. A coated medical implant or medical device comprising a coating according to any one of claims 1 to 7 and a base body.

9. A medical implant according to claim 8, wherein it is a permanent implant.

10. A medical implant or medical device according to claim 8 or 9, wherein the main body of the implant comprises durable materials, in particular titanium or titanium alloys, steels, ceramics, glasses and polymeric implant materials.

11. A medical implant or medical device according to claim 8, wherein the base body of the implant comprises biodegradable material, in particular consists of a magnesium material of magnesium or magnesium alloy. Medical implant or medical device according to one of claims 8 to 11, which are implants used in medicine, in particular in osteosynthesis, in particular bone fasteners such as screws, plates or nails, surgical sutures, intestinal staples, vascular clips, or Prostheses in the field of hard and soft tissues.

A medical implant according to claim 12, which is endoprostheses, such as implants in the bone cartilage region, in particular artificial joints or parts of artificial joints.

A medical implant according to any one of claims 8 to 13, wherein an intermediate layer is disposed between the coating and the base body.

A method of manufacturing a coated medical implant or medical device comprising the step of coating the medical implant or medical device with a coating comprising LDH defined in any of claims 1 to