Bone implant body and method for the production of same

Abstract

The invention relates to a bone implant body (1) intended to be introduced into a bone defect site to promote bone growth in this bone defect site. The bone implant body comprises: a main body (20) made of a deformable and porous collagen matrix, which contains at least one main-body collagen material from a first amount in the form of a mineralised collagen and a second amount in the form of a native collagen; and a depositing element (3) which is completely embedded in the main body (2) such that it is completely surrounded by the collagen matrix of the main body (2) and is placed centrally within the main body (20), and which, as a first component, contains at least one depositing material in the form of a bioactive substance that promotes bone healing; wherein a transition between the collagen matrix of the main body (2) and the depositing element (2) is formed by a boundary (4) of the depositing element (3).

Description

[0001] Bone implant body and method for its manufacture

[0002] The invention relates to a bone implant body for insertion into a bone defect site to promote bone growth in this bone defect site and to a method for producing such a bone implant body.

[0003] Bone defects can occur due to illness and / or medical treatment. One example is the wound cavity after the removal of a bone cyst. The periodontal pocket (or alveolus) that remains after a tooth extraction can also be considered a special case of such a bone defect.

[0004] If the bone's self-healing capacity does not lead to healing within an acceptable period of time, the use of substitute materials is necessary. The best results in bone regeneration are achieved with autologous (the patient's own) bone tissue. After blood, it is the second most frequently transplanted human tissue. In addition to the bone matrix, it also contains stem cells and growth factors. Disadvantages include its limited availability and the risks and stress for the patient due to the additional surgery required to harvest the patient's own bone tissue. Bone tissue from other donors (allogeneic) and animals (xenogeneic) is also used as bone substitute material (BEM). Here, cells and bioactive substances are deactivated through processing steps such as decellularization, deimmunogenization, and / or sterilization. In addition, biodegradable, artificial bone substitute materials are increasingly being used.Such an artificial bone substitute material should be biocompatible, bioresorbable, sterilizable without loss of function, and capable of being processed into three-dimensional structures of variable size. Furthermore, it should not release cytotoxic substances, allow for adhesion and cell ingrowth, and exhibit sufficient mechanical stability.

[0005] Collagen-based bone substitute materials, e.g., in combination with a calcium phosphate mineral phase, simulate the native bone matrix and are therefore suitable bone substitute materials. Various strategies exist for introducing a mineral phase into the collagen structure, ranging from simply mixing ceramic calcium phosphate granules and powders to the simultaneous deposition of nanocrystalline hydroxyapatite during collagen fibril reassembly, as described, for example, in EP 0 945 146 A2 and EP 0 945 147 A2. However, such mineralized collagen can be highly brittle and disintegrate under mechanical stress. These mechanical properties make it difficult to introduce into a bone defect.

[0006] DE 10 2005 034 421 A1 describes a bioresorbable mineralized material for filling bone defects, which has a collagen matrix made up of aggregated collagen chains, whereby only the surface of the aggregated collagen chains is mineralized.

[0007] DE 199 62 090 A1 describes a hollow shaped body serving as a bone substitute, with the geometry of a bone or a bone fragment. The shaped body is made of optionally mineralized collagen in the form of a dense network of collagen fibrils, optionally with an additional matrix of calcium phosphate cement, with the collagen fibrils embedded in the calcium phosphate cement matrix. One object of the invention is to provide a bone implant body of the type described above with improved properties compared to the prior art.

[0008] To achieve this object, a bone implant body according to the features of patent claim 1 is specified. The bone implant body according to the invention has a base body made of a deformable and porous collagen matrix, which contains at least one base body collagen material consisting of a first portion in the form of a mineralized collagen and a second portion in the form of a native collagen, and a depot element that is completely embedded in the base body so that it is completely surrounded by the collagen matrix of the base body and positioned centrally within the base body, and contains as a first component at least one depot substance in the form of at least one bioactive substance that promotes bone healing, wherein a transition between the collagen matrix of the base body and the depot element is formed by an interface of the depot element.

[0009] Mineralized collagen is understood here to mean collagen that, in addition to the actual collagen preparation process, has undergone a further treatment step, particularly to provide it with a mineral phase that supports bone formation at the bone defect site. Such mineralized collagen and a method for its production are known, for example, from EP 0 945 146 A2.

[0010] Native collagen, in this context, refers to collagen that, unlike mineralized collagen, contains essentially no foreign substances. In this respect, it can also be described as mineral-free. It may contain only a small amount of foreign substances originating from the collagen processing process, which, however, are not considered significant. In this respect, native collagen can also be described as pure or clean, or, since it has not undergone any further treatment steps beyond the actual collagen processing process, as untreated or original.

[0011] The collagen matrix and thus the bone implant body as a whole are deformable, in particular plastically or irreversibly deformable, and preferably also compressible. This means that only a single size of the bone implant body needs to be manufactured and kept in stock, which is very advantageous from an economic point of view. The bone implant body, which is only available in one size, can nevertheless be used in bone defects of very different sizes due to its advantageous mechanical properties. Due to its plastic deformability and, if necessary, also due to its compressibility, it can advantageously be adapted to the respective dimensions of the bone defect in question. This adaptation is carried out by the surgeon or the treating physician. Plastic deformability refers in particular to the ability of the collagen matrix orThis also applies to the bone implant body as a whole, to irreversibly deform or reshape itself under the application of force after exceeding its elastic limit and to retain this shape once the force is removed. Such permanent deformation of the bone implant body is advantageous because a bone implant body that has been deformed by the surgeon according to the shape and size of the bone defect and then inserted into the bone defect should, if possible, not exert any restoring forces on the tissue surrounding the bone defect in order to avoid impairing the healing process. Such undesirable restoring forces could occur, however, if the deformation is not permanently plastic, but only elastic. Furthermore, the bone implant body has good stability against mechanical stress.

[0012] The bone implant body and also the depot element can, in particular, have a cylindrical shape. Other geometries, such as a truncated cone or cuboid shape, are also possible. In the cylindrical configuration, the bone implant body has a diameter in particular in the range between 0.8 cm and 2.0 cm, preferably in the range between 1.2 cm and 1.6 cm, and a length or height in particular in the range between 1.2 cm and 2.0 cm, preferably in the range between 1.4 cm and 1.8 cm, and preferably 1.6 cm. The volume of the depot element is in particular between 10% and 40%, preferably between 15% and 30% of the total volume of the bone implant body.

[0013] Mineralized collagen does not, or at least not readily, exhibit these desirable mechanical properties, such as deformability and / or compressibility. Mineralized collagen actually exhibits the opposite behavior. It can be solid, stiff, and brittle. On the other hand, due to the embedded mineral phase, it promotes bone growth. To ensure that the base body and the bone implant body as a whole exhibit the desired mechanical properties, such as deformability, compressibility, and the like, the base body collagen material contains native collagen in addition to mineralized collagen. The latter produces these desired mechanical properties. Furthermore, native and mineralized collagen, like all collagen, have a good hemostatic (= blood-clotting) effect, which promotes wound healing.

[0014] The additional porosity of the collagen matrix allows the growth of new (bone) cells into the pores of the collagen matrix, thereby promoting the bone healing process.

[0015] The bioactive substance in the depot substance serves to stimulate new bone formation. It is, in particular, a growth factor that promotes bone growth. Like mineralized collagen, it supports bone formation at the bone defect site. The depot element can also contain a combination of at least two bioactive substances that promote bone healing as a depot substance.

[0016] It has been recognized that after introducing collagen material loaded with a bioactive substance into a bone defect, a very rapid release of the bioactive substance often occurs. To enable a longer-lasting, controlled release of the active ingredient, the depot element containing the bioactive substance of the depot substance is completely embedded in the base body. The bone implant body according to the invention therefore has no layered structure. Rather, the depot element is completely surrounded by the collagen matrix of the base body. It is positioned centrally or centrally within the base body. This also ensures that the depot substance is released as evenly as possible outwardly to the bone defect in all directions.The transition formed by the interface of the depot element between the collagen matrix of the main body and the depot element is, in particular, not fluid, but rather preferably sharp or abrupt. The interface is, in particular, the outer boundary wall of the depot element. This abrupt transition results, in particular, from the advantageously separate production of the depot element, independent of the production of the collagen matrix.

[0017] Advantageous embodiments of the bone implant body according to the invention result from the features of the claims dependent on claim 1.

[0018] A favorable design is one in which the collagen matrix of the base body consists exclusively of the base body collagen material. Its structure is then particularly simple. It can be produced with relatively little effort, especially on an industrial scale.

[0019] According to a further advantageous embodiment, the base body collagen material is a mixture, in particular a homogeneous mixture, of mineralized collagen and native collagen. Another combination of mineralized collagen and native collagen is also particularly possible. However, with regard to the best possible and uniform deformability and compressibility of the base body and also of the bone implant body as a whole, it is advantageous if the mineralized collagen and native collagen are mixed as thoroughly as possible. According to a further advantageous embodiment, the volume ratio of the mineralized collagen to the native collagen in the base body collagen material is in the range between 20:80 and 80:20, preferably between 25:75 and 75:25, more preferably between 30:70 and 70:30, and particularly preferably 60:40.

[0020] According to a further advantageous embodiment, the depot element is a separately storable component. In particular, the depot element has a maximum moisture content of 20%.

[0021] According to a further advantageous embodiment, the depot element contains a depot collagen material as a further (particularly second) component. The depot collagen material consists, in particular, of only mineralized collagen or of both mineralized collagen and native collagen. In addition to the depot substance as the first component, the depot element contains the depot collagen material as a further or second component. It can thus be easily embedded into the collagen matrix of the base body and also provides a mineral phase contribution for bone growth.

[0022] According to a further advantageous embodiment, the bone implant body contains a delaying agent that delays the release of the depot substance. The delaying agent is in particular heparin. The delaying agent is preferably present in the depot element, in particular as a third component. However, it can also be present additionally or alternatively in the base body. The delaying agent strengthens the binding of the at least one bioactive substance of the depot substance within the bone implant body and thus slows the release of the at least one bioactive substance. By means of the delaying agent, the release of the depot substance can be specifically adjusted, in particular slowed down, in order to thereby maintain the bone healing-promoting effect of the depot substance over a longer period.

[0023] According to a further advantageous embodiment, the mineralized collagen contains a mineral phase in the form of mineral crystallites, wherein the mineral crystallites have a maximum dimension of, in particular, at most 1 pm (micrometer), and preferably of at most 100 nm (nanometer), and the mineral crystallites are preferably calcium phosphate crystallites, most preferably hydroxyapatite crystallites. The mineral crystallites are arranged, in particular, within collagen fibrils. However, they can also surround the collagen fibrils, in particular externally. The mineral crystallites are preferably aligned along the orientation of the collagen fibrils. The mineral crystallites have a minimum dimension of, in particular, at least 0.5 nm.

[0024] According to a further advantageous embodiment, the mineralized collagen is cross-linking-free. By “cross-linking-free” we mean that although a small amount of natural cross-linking (or basic cross-linking) may be present, there is no further externally introduced cross-linking, such as chemical or enzymatic cross-linking. Such further cross-linking, which can also be referred to as synthetic, is formed in particular through the use of an artificial cross-linker. This can be achieved, for example, by means of a subsequent chemical (cross-)linking process. The cross-linking-free mineralized collagen relevant here has been produced without the use of such an artificial cross-linker. It is stronger, more brittle, and stiffer than mineralized collagen specifically cross-linked using an artificial cross-linker. Furthermore, the cross-linking-free mineralized collagen relevant here can be unstable with regard to mechanical deformation.In this respect, it exhibits less favorable mechanical properties than synthetically cross-linked mineralized collagen. However, this is deliberately accepted because an artificial cross-linker could adversely affect the depot substance, impairing its bone-healing-promoting effect and, in the worst case, even completely losing it. To prevent this, the use of an artificial cross-linker is avoided here. To achieve the desired mechanical properties, at least the basic collagen material contains native collagen in addition to the advantageously cross-link-free mineralized collagen.

[0025] According to a further advantageous embodiment, at least one collagen from the group of mineralized collagen and native collagen is an atelocollagen, in particular an atelocollagen of equine origin, and preferably a type 1 atelocollagen of equine origin. It is therefore possible that the mineralized collagen or the native collagen is such an atelocollagen. This can also apply to both. Such an atelocollagen exhibits particularly high biocompatibility. The human body can degrade or reabsorb it very well. Collagen of equine origin is obtained primarily from horse tendons.

[0026] According to a further advantageous embodiment, the bioactive substance promoting bone healing is at least one active ingredient from the group of VEGF, TGF-ß, BMP-2, BMP-4, BMP-7, another member of the BMP family, PDGF-BB, another member of the PDGF family, SDF-1a, EGF, bFGF1, bFGF2, dexamethasone, hydrocortisone, and cholecalciferol, or contains such an active ingredient. Likewise, the bioactive substance promoting bone healing can be at least one active ingredient mixture from the group of human blood plasma (e.g., FFP), human serum, human platelet concentrate (e.g., PL, PRGF, PRP), and hypoxia-conditioned medium concentrate, or contain such an active ingredient mixture. VEGF, TGF-ß, BMP-2, BMP-4, BMP-7, PDGF-BB, SDF-1a, EGF, bFGF1 and bFGF2 are proteins that can be produced biotechnologically, particularly with the help of genetically modified organisms.The blood plasma, serum, and platelet concentrate also mentioned can be obtained, in particular, from human blood. The hypoxia-conditioned medium concentrate is produced, in particular, from cell cultures. In principle, other active ingredients and / or active ingredient mixtures are also possible. For example, the bioactive substance promoting bone healing can be an active ingredient from the group consisting of members of the TGF-ß superfamily, members of the BMP family, the growth differentiation factors (GDFs), ADMP-1, members of the fibroblast growth factor family, members of the hedgehog protein family, members of the insulin-like growth factor (IGF) family, members of the platelet-derived growth factor (PDGF) family, members of the interleukin (IL) family, and members of the colony-stimulating factor (CSF) family. The bioactive substance promoting bone healing is, in particular, a growth factor.

[0027] According to a further advantageous embodiment, at least one component from the group consisting of the base body and the depot element contains an antimicrobial, antibiotic, wound-healing, or anti-inflammatory substance. It is therefore possible for the base body and / or the depot element to contain at least one of these active ingredients. This antimicrobial substance contributes to preventing and / or combating infections. It is preferably a locally tolerated antiseptic, such as polihexanide, octenidine, silver (particularly silver compounds or silver particles), iodine derivatives, chlorhexidine, triclosan, or the like. Likewise, an antibiotic substance suitable for local application, such as gentamicin, metronidazole, vancomycin, clindamycin, or the like, can be used.

[0028] A further object of the invention is to provide a method for producing a bone implant body of the type described at the outset with improved properties compared to the prior art.

[0029] To achieve the object of the method, a method according to the features of claim 13 is provided. In the method according to the invention, the depot element is first produced separately. The depot element, which is particularly storable, is then incorporated as a finished component into a collagen-containing matrix base substance during the production of the collagen matrix of the base body.

[0030] The collagen-containing matrix ground substance is intended in particular for the formation of the collagen matrix of the basic body.

[0031] The sequential and essentially independent production of the depot element and the collagen matrix of the base body simplifies manufacturing. Furthermore, it is possible to prefabricate and store the depot element until it is needed to manufacture the complete bone implant body. This also simplifies manufacturing and, in particular, the associated logistics.

[0032] The method according to the invention and its embodiments offer essentially the same advantages that have already been described in connection with the bone implant body according to the invention and its embodiments.

[0033] Some advantageous embodiments of the method according to the invention result from the features of the claims dependent on claim 13.

[0034] A favorable embodiment is one in which the depot element is produced by freeze-drying a collagen-containing depot base substance to which the at least one depot substance has been added.

[0035] According to another advantageous embodiment, the collagen matrix of the base body is produced by freeze-drying the collagen-containing matrix substance after the depot element has been introduced into the collagen-containing matrix substance. Both native collagen and mineralized collagen can be advantageously processed into porous structures by freeze-drying.

[0036] Further features, advantages, and details of the invention will become apparent from the following description of exemplary embodiments with reference to the drawing. Fig. 1 shows an exemplary embodiment of a bone implant body intended for insertion into a bone defect site, with a depot element embedded in a collagen matrix, in a perspective schematic representation.

[0037] Fig. 2 shows the bone implant body according to Fig. 1 in a schematic cross-sectional view,

[0038] Fig. 3 a diagram with pressure-compression curves of different collagen-containing molded bodies,

[0039] Fig. 4 Examples of molded bodies containing different collagens after carrying out a brittleness test,

[0040] Fig. 5 and 6 SEM images of the pore structure of a molded body made of mineralized collagen,

[0041] Fig. 7 an EDX spectrum of mineralized collagen,

[0042] Fig. 8 a TEM image of mineralized collagen,

[0043] Fig. 9 a diagram showing the time course of the release of the bioactive substance BMP-2 from depot elements with different mineralized collagen materials,

[0044] Fig. 10 is a diagram showing percentage releases of the bioactive substance BMP-2 from depot elements with various mineralized collagen materials over a period of 14 days, and Fig. 11 is a sample of the bone implant body according to Fig. 1 in a photographic cross-sectional view comparable to the schematic cross-sectional view of Fig. 2.

[0045] Corresponding parts in Figs. 1 to 11 are provided with the same reference numerals. Details of the exemplary embodiments explained in more detail below may also constitute an invention in themselves or be part of a subject matter of the invention.

[0046] 1 and 2 each show a schematic line representation of an embodiment of a bone implant body 1 which is intended for insertion into a bone defect. In the embodiment shown, it has a cylindrical shape. Other shapes not shown, such as a truncated cone, are also possible. The bone implant body 1 has a base body 2 made of a collagen matrix and a depot element 3 completely embedded in the collagen matrix of the base body 2. The transition between the depot element 3 and the collagen matrix of the base body 2 is not smooth, but abrupt. It is formed by an outer boundary surface 4 of the depot element 3. Fig. 11 shows a photograph of a realized sample of the bone implant body 1. The photograph shows approximately the same cross-sectional view as the schematic line drawing in Fig. 2. In the embodiment shown in Fig.In the pattern shown in Figure 11, depot element 3 is colored to make it easier to recognize.

[0047] The collagen matrix material of the particularly plastically deformable and preferably also compressible base body 2 consists of a homogeneous mixture of mineralized collagen as the first component and native collagen as the second component. In the illustrated embodiment, the volume ratio of mineralized collagen to native collagen is 60 to 40. Other volume ratios not shown, such as 80 to 20, are also possible.

[0048] Depot element 3 contains, as one component, a depot collagen material composed of 100% mineralized collagen. Another component of depot element 2 is a depot substance that promotes bone healing, which in the illustrated embodiment is the bioactive substance BMP-2, a growth factor. Furthermore, depot element 3 contains, as a further component, a delaying substance that delays the release of the growth factor BMP-2; in the illustrated embodiment, this is heparin.

[0049] Both the base body 2 and the depot element 3 consist either entirely or at least substantially of collagen-containing material. In the base body 2, the collagen matrix consists of a mixture of mineralized collagen and native collagen. The collagen-containing material of the depot element 3, in contrast, consists only of mineralized collagen, to which the growth factor BMP-2 and the retarding agent heparin are also added. The production of these different collagen-containing materials is described below.

[0050] Production of a mineral collagen suspension. The production and use of mineralized collagen is described, for example, in DE 10 2004 044 102 B4 and EP 0 945 146 A2. The process used here is based on these already known methods.

[0051] In a 2-liter Erlenmeyer flask, dissolve 1 g of acid-soluble collagen (type 1 atelocollagen of equine origin from Resorba Medical GmbH in Nuremberg, Germany) in 1 l of 10 mmol / l HCl (prepared from 100 ml of 0.1 mol / l HCl and 900 ml of deionized water) while stirring vigorously (using a large stir bar / magnetic stirrer). While continuing to stir vigorously, the following are added in sequence:

[0052] 1) 180 ml 0.1 mol / l CaC12 solution

[0053] 2) 120 ml 2 mol / 1 NaCl solution

[0054] 3) 168 ml 0.5 mol / l TRI S buffer solution (pH = 7.5)

[0055] 4) 500 ml deionized water

[0056] 5) 22.6 ml of Sörensen phosphate buffer (0.5 mol / l; pH = 7.4)

[0057] When the phosphate buffer is added, the solution becomes cloudy due to precipitating calcium phosphates. Finally, the solution is filled to 2.0 l with deionized water. Stir vigorously for about 1 minute, then cap the flask and place it in a heat bath at 37 °C for 12-24 hours.

[0058] The mineralized collagen is separated by centrifugation. The gelatinous precipitate is vigorously stirred and then transferred to centrifuge tubes (e.g., 30 ml plastic tubes). It is centrifuged for 23 minutes at 5200 rpm in a refrigerated centrifuge at 4°C to prevent warming of the product, and then the supernatant is poured off. The suspension is then added, and the centrifugation is repeated until the entire batch has been appropriately treated. After the final pouring of the supernatant, the pellets are removed from the tubes with a spoon spatula and collected in a 125 ml beaker. While stirring with a heavy-duty stir bar, just enough deionized water is added dropwise until a pourable mineral-collagen suspension is formed.

[0059] Preparation of a mineral-collagen suspension with heparin

[0060] The preparation is essentially analogous to the preparation of the mineral collagen suspension described above. The only difference is that after the addition of the phosphate buffer, a defined amount of heparin (5 mg / g collagen to 150 mg / g collagen), pre-dissolved in deionized water, is added. All other steps remain the same. The final result is a mineral collagen suspension with heparin.

[0061] Preparation of a native collagen suspension

[0062] Acid-soluble collagen (type 1 atelocollagen of equine origin from Resorba Medical GmbH in Nuremberg, Germany) is dissolved in a concentration between 1 mg / ml and 35 mg / ml in 0.1 M HCl or 6-13 mM acetic acid.

[0063] The different collagen suspension variants (mineral collagen suspension without and with heparin, native collagen suspension) are filled into blister packs and freeze-dried as individual components or as a mixture in different ratios, for example with a volume ratio of mineralized collagen to native collagen of 60 to 40 or 80 to 20.

[0064] The production of the bone implant body 1 with the depot element 3 takes place in two steps:

[0065] First, the depot element 3 is produced from the collagen suspension variants described above—in this example, only from a mineral collagen suspension with heparin—and loaded with a depot substance in the form of a bioactive substance—in this example, the growth factor BMP-2. The resulting depot element, still liquid and containing collagen, is filled into a blister pack. The depot element 3 is then freeze-dried, producing the depot element 3 as an intermediate product that is particularly storable in this state. The depot element 3 has a (residual) moisture content of only approximately 10% to 15% and is therefore very easy to store.

[0066] The collagen-containing matrix base substance of the collagen matrix of the base body 2 is also produced from the collagen suspension variants described above, in the exemplary embodiment as a mixture of the mineral collagen suspension and the native collagen suspension in the desired volume ratio, e.g., 60 to 40 or 80 to 20. In another exemplary embodiment, however, the matrix base substance can also be produced solely from native collagen suspension. This collagen-containing matrix base substance is then filled in liquid form into a blister mold that has a larger diameter than the mold of the depot element 3. The previously produced depot element 3 is either pressed into the liquid matrix base substance, with the matrix base substance flowing around the depot element 3, or the depot element 3 is placed on a blister mold half-filled with matrix base substance, which is then filled with matrix base substance.After subsequent freeze-drying, both variants lead to the complete inclusion of the depot element 3 within the collagen matrix of the base body 2 and the final product is present in the form of the bone implant body 1.

[0067] In the following, properties of this bone implant body 1 or of the collagen-containing materials used for its production are described with reference to Figures 3 to 10.

[0068] Fig. 3 shows a diagram with the results of compression tests on various truncated cone-shaped collagen-containing molded bodies. The tests were carried out on molded bodies in an essentially dry state using a Zwick materials testing machine equipped with a 1 kN load cell. All molded bodies were tested at room temperature. They were compressed to up to 40% of their original length (e.g., 1.6 cm). The diagram in Fig. 3 plots the applied pressure ("stress"), which corresponds to the compression force, against the resulting mechanical strain or compression of the molded bodies.Curve 5 shows the curve for a molded article made solely of native collagen, curve 6 the curve for a molded article made solely of a mixture of mineralized collagen and native collagen with a volume ratio of 60:40, curve 7 the curve for a molded article made solely of a mixture of mineralized collagen and native collagen with a volume ratio of 80:20, and curve 8 the curve for a molded article made solely of uncrosslinked mineralized collagen. The highest compressibility is achieved by molded articles made solely of native collagen (curve 5). However, molded articles made solely of mixtures of mineralized and native collagen (curves 6 and 7) also have almost as good compressibility as molded articles made solely of native collagen, and in any case significantly better compressibility than molded articles made solely of uncrosslinked mineralized collagen (curve 8).Molded bodies made from blends of mineralized and native collagen exhibit lower resistance to compression. A proportion of just 20% native collagen significantly reduces the pressure required for a 25% compression compared to a molded body consisting solely of uncrosslinked mineralized collagen. The addition of native collagen therefore increases the compressibility and deformability of the molded body.

[0069] Fig. 4 shows the results of brittleness tests conducted on molded bodies made of various collagen materials. In this test, the cylindrical molded bodies, each 8 mm long and 6 mm in diameter, were subjected to shear forces. For this purpose, they were rolled back and forth 2 cm each on a flat surface under compressive load. This process was repeated three times. A metal plate with a grooved surface (8 grooves per cm, depression 0.3 mm) was used to apply the shear pressure load. The compressive load was approximately 1.2 N. The molded body 9 shown on the left in Fig. 4 consisted of uncrosslinked mineralized collagen, the molded body 10 shown in the middle of crosslinked mineralized collagen, and the molded body 11 shown on the right of a mixture of mineralized collagen and native collagen with a volume ratio of 60:40.Forms 9 and 10 have disintegrated into individual pieces, whereas form 11 remains intact. The addition of native collagen therefore reduces the brittleness of the form.

[0070] Overall, the addition of native collagen has a positive effect on the mechanical properties of the examined molded bodies and thus also of the bone implant body 1.

[0071] Figs. 5 and 6 show images of the structure of molded bodies made of mineralized equine collagen, taken using scanning electron microscopy (SEM). These molded bodies exhibit a uniform, interconnecting pore structure with pore diameters of up to 100 μm. This pore structure is not affected by the insertion of the depot element 3 into the collagen matrix of the base body 2. Nothing can be seen that could impair the stability of the molded body. The pores in the collagen material of the bone implant body 1 are beneficial because they allow the ingrowth of new bone cells.

[0072] Figure 7 shows a spectrum from an energy-dispersive X-ray spectroscopy (EDX) analysis of a portion of a mineralized collagen sample. Peaks 12a and 12b demonstrate that the sample has a higher content of phosphorus (peak 12a) and calcium (peak 12b) than would be the case for a native collagen sample. The sample contains hydroxyapatite.

[0073] Figure 8 shows an image of mineralized collagen taken using transmission electron microscopy (TEM). The morphology of the hydroxyapatite crystallites 13 is evident. The dimensions of the hydroxyapatite crystallites 13 are in the nm range. The longitudinal extension of the hydroxyapatite crystallites 13 is approximately 100 nm.

[0074] The diagrams in Fig. 9 and 10 relate to the release of the depot substance stored in depot element 3 in the form of the growth factor BMP-2. Fig. 9 shows the time courses of the cumulative amounts of released BMP-2 for depot elements 3 with various mineralized collagen materials. The cumulative amounts of released BMP-2 (y-axis) are plotted against time (x-axis). Curve 14 shows the release course for a depot element 3 made of mineralized collagen of bovine origin, curve 15 the release course for a depot element 3 made of mineralized collagen of equine origin, and curve 16 the release course for a depot element 3 made of mineralized collagen of equine origin with heparin as a delay agent.

[0075] Figure 10 shows the cumulative percentage release of the growth factor BMP-2 from depot elements containing various mineralized collagen materials over a period of 14 days. The right bar 17 shows the cumulative percentage release rate for a depot element 3 made of mineralized collagen of bovine origin, the left bar 18 shows the cumulative percentage release rate for a depot element 3 made of mineralized collagen of equine origin, and the middle bar 19 shows the cumulative percentage release rate for a depot element 3 made of mineralized collagen of equine origin with heparin as a delaying agent.

[0076] Figures 9 and 10 show that mineralized collagen of equine origin binds BMP-2 significantly better than native collagen (not shown in Figures 9 and 10) and mineralized collagen of bovine origin. The addition of the retarding agent heparin further increases the binding capacity. The higher the binding capacity, the lower the release rate. A bone implant body 1 with the lowest possible BMP-2 release rate is advantageous, as the growth factor BMP-2 can then support bone healing over a longer period.

[0077] The release rate can be adjusted to a desired value by adjusting the amount of delay agent added.

Claims

Patent claims 1. A bone implant body for insertion into a bone defect site to promote bone growth in this bone defect site, comprising a) a base body (2) made of a deformable and porous collagen matrix which contains at least one base body collagen material consisting of a first portion in the form of a mineralized collagen and a second portion in the form of a native collagen, and b) a depot element (3) which is completely embedded in the base body (2) so that it is completely surrounded by the collagen matrix of the base body (2) and is placed centrally within the base body (2), and contains, as a first component, at least one depot substance in the form of at least one bioactive substance which promotes bone healing, wherein a transition between the collagen matrix of the base body (2) and the depot element (3) is formed by an interface (4) of the depot element (3).

2. Bone implant body according to claim 1, characterized in that the collagen matrix of the base body (2) consists exclusively of the base body collagen material.

3. Bone implant body according to claim 1 or 2, characterized in that the basic body collagen material is a mixture, in particular a homogeneous mixture, of the mineralized collagen and the native collagen.

4. Bone implant body according to one of the preceding claims, characterized in that in the basic body collagen material a volume ratio between the mineralized collagen and the native collagen is in the range between 20 to 80 and 80 to 20, preferably between 25 to 75 and 75 to 25 and preferably between 30 to 70 and 70 to 30 and particularly preferably 60 to 40.

5. Bone implant body according to one of the preceding claims, characterized in that the depot element (3) is a separately storable component and in particular has a moisture content of at most 20%.

6. Bone implant body according to one of the preceding claims, characterized in that the depot element (3) contains a depot collagen material as a further component, and the depot collagen material consists in particular only of mineralized collagen or of both mineralized collagen and native collagen.

7. Bone implant body according to one of the preceding claims, characterized in that it contains a delaying agent which delays the release of the depot substance, and the delaying agent is in particular heparin.

8. Bone implant body according to one of the preceding claims, characterized in that the mineralized collagen contains a mineral phase in the form of mineral crystallites, wherein the mineral crystallites have a maximum extension of in particular at most 1 pm, and preferably of at most 100 nm, and the mineral crystallites are preferably calcium phosphate crystallites, most preferably hydroxyapatite crystallites.

9. Bone implant body according to one of the preceding claims, characterized in that the mineralized collagen is produced without the use of an artificial crosslinker and is thus free from synthetic crosslinking.

10. Bone implant body according to one of the preceding claims, characterized in that at least one collagen from the group of mineralized collagen and native collagen is an atelocollagen, in particular an atelocollagen of equine origin, and preferably a type 1 atelocollagen of equine origin.

11. Bone implant body according to one of the preceding claims, characterized in that the bioactive substance promoting bone healing is or contains at least one active ingredient from the group of VEGF, TGF-ß, BMP-2, BMP-4, BMP-7, another member of the BMP family, PDGF-BB, another member of the PDGF family, SDF-1a, EGF, bFGF1, bFGF2, dexamethasone, hydrocortisone and cholecalciferol, or the bioactive substance promoting bone healing is or contains at least one active ingredient mixture from the group of human blood plasma, human serum, human platelet concentrate and hypoxia-conditioned medium concentrate.

12. Bone implant body according to one of the preceding claims, characterized in that at least one component from the Group of basic body (2) and depot element (3) contains an antimicrobial, antibiotic, wound-healing or anti-inflammatory substance.

13. A method for producing a bone implant body (1) for insertion into a bone defect site to promote bone growth in this bone defect site according to one of the preceding claims, wherein a) the depot element (3) is first produced separately, and b) the depot element (3) is then introduced as a finished partial component into a collagen-containing matrix base substance during the production of the collagen matrix of the base body.

14. The method according to claim 13, characterized in that the depot element (3) is produced by freeze-drying a collagen-containing depot base substance to which the at least one depot substance has been added.

15. The method according to claim 13 or 14, characterized in that the collagen matrix of the base body (2) is produced after introduction of the depot element (3) into the collagen-containing matrix base substance by freeze-drying the collagen-containing matrix base substance.

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