Technology area

The invention is related to the product intended for facilitation of bone ossification, which is usable for implantation in bone defects, in controlled bone regeneration, filling of bone cysts and smaller missing parts of the bones or as a food supplement that supports ossification.

Present technology status

A common clinical procedure of implantation of the osteoinductive, i.e. bone formation supporting materials, uses so-called autograft where the needed part of bone is removed from another place of the patient's body. However, the amount of bone which can removed from the patient is limited and the own approach is considerably invasive. Less traumatic option is to use allograft when the bone is taken from a deceased donor. This process is somewhat problematic due to the risk of transmission of infectious diseases whereas these implants contain only a small amount of growth factors because they do not contain living cells.

To avoid the risk of infection an array of various artificial products have been developed and marketed which substitute human bone implants. A bulk of procedures for preparing of collagen- hydroxyapatite composites for surgical treatment of bone defects have been described. To obtain hydroxyapatite some procedures use bones of vertebrates and animal collagen, mainly of type I, which is most often obtained from animal fibrous tissues.

The hydroxyapatite osteoinductive compounds are commercially available also as the products isolated from the heat-modified mineral material of sea corals, or they are produced synthetically by precipitation of calcium and phosphate ions in aqueous ammoniacal environment.

The problem of these synthetic hydroxyapatite products can be their cytotoxicity caused by ammonia and ammonium compounds from the reaction environment, which can be very difficult to remove from the product. The ratio of calcium and phosphorus (Ca/P) in the synthetic products may differ from the native bones, and is usually in the range from 1.62 to 1.69.

The mineral apatite component is, with the advantage, created by precipitation of calcium compounds by phosphates in aqueous collagen dispersions. In such created composites the orientation of collagen macromolecules and the longitudinal axis of the hydroxyapatite microcrystals can be to some extent identical which can be controlled by adjusting the acidity and temperature of the precipitation environment. However, the exact replica of the native composite, which is a structurally inclusion compound of clactrate type is unreachable by the synthetic route. Many manufacturers produce mineral sintered compounds, i.e. heat treated; however they differ chemically from the biological carbonate form of apatite which can found in bones. It was found that these adjusted phosphate salts were less degradable compared to the natural carbonate forms.

Another deficiency of the known solutions which are based on the natural composites is the antigenicity of animal collagen though it is only mild in majority of patients. The reasons of the antigenicity are the antigenic determinants, i.e. specific aminoacid sequences in collagen which are different in various animal species. They are located mainly in the telopeptidic terminal areas of the collagen protein. However, this disadvantage can become a serious problem in patients with allergy to foreign proteins. A disposition of the patient to increased or even allergic reaction to a foreign collagen may not be known before the surgery and this risk is, as well as the proportion of people with allergies in the population due to lifestyle factors increasing.

For type I collagen which is used for the preparation of absorbable haemostatics the allergen telopeptides can be eliminated using the specific enzymatic process called atelopeptidation. However, the atelopeptidic modification of collagen in the native bone composites has not been described yet. Only preparation of a synthetic bone composite using a modified atelocollagen instead of collagen is known.

Invention rationale

The product for facilitation of bone ossification according to the invention contributes to elimination of the above stated deficiencies of the known technology status which consists of the native composite of the hydroxyapatite structure with collagen. A principle of the invention lies in the fact that the collagen contained in the native bone composite is modified, at least partially devoid of the terminal antigenic telopeptides, which is a reaction product of enzymatic atelopeptidation.

Besides the basic ingredient - the native bone composite with modified collagen, the product may, as the advantage, further contain at least one excipient from the group comprising growth factors, antibiotics, bacteriostatic or pharmacologically active substances.

The principle of the method of manufacture of the product that facilitates bone ossification according to the invention lies in the fact that proteolytic enzymes are applied on the purified bone mash and these enzymes catalyze hydrolysis of terminal collagen telopeptides and so they modify collagen by means of atelopeptidation.

It is at the same time advantageous if the bone structures and non-collagen organic components are removed from the bone mash before atelopeptidation.

A proteolytic enzyme without any collagenolytic activity, preferably pepsin, should be used with the advantage for atelopeptidation.

The bone composite of the invention combines the properties of the preserved natural bone mineral structure and collagen component with the advantage of the suppressed antigenicity of the used animal collagen. This new effect is, as already mentioned, achieved by atelopeptidation, i.e. by hydrolysis of the collagen telopeptides catalyzed by the appropriate specific proteolytic enzymes, which are chosen so as not to damage the main triple helical areas of collagen. The atelopeptidic reaction is, with the advantage, carried out on the purified bone mash from which other non- collagen organic components had been previously removed. The modified collagen is present in the bone mash in the insoluble form and the process of atelopeptidation has the character of heterogeneous reaction. The area of a phase boundary is important for the kinetics of the heterogeneous reactions. The bone structure is porous, has a relatively large internal surface and its capillary network is permeable for enzymes; despite it, its disintegration into smaller particles is however convenient which increases the interphase surface, decreases the diffusion distances for reactants and accelerate the progress of the enzymatic reactions.

Using of the product that facilitates ossification of bones of the invention may lie in its surgical implantation in the processes of controlled bone regeneration or for filling of bone cysts and smaller missing parts of bones or in the application of this product as a food supplement that supports ossification.

Another potential use of the product of the invention is the administration as a food supplement to support bone ossification in persons at the time of increased demands for growth or in people with osteoporosis, arthritis and other degenerative illnesses.

Examples of invention implementation

Example 1

An example of the product of the invention is a sterile composite of the native hydroxyapatite and atelocollagen - i.e. the collagen from which at least the terminal antigen telopeptides had been removed which is a reaction product of the enzymatic atelopeptidation - in the natural structural complex.

The manufacturing process of the atelocollagen bone composite in the exemplary performance consists in the separation of the central part of the tarsal bovine bones, cleaning of their surface and marrow cavity, crushing into the small grit with an average particle size of 4.0 to 0.1 mm, extraction of fat components using gasoline, drying under reduced pressure, repeated extraction of cellular globular proteins by 10% aqueous sodium chloride solution, followed by extraction with aqueous solutions of diluted acetic acid and then by atelopeptidation which consists in incubation of the grit suspension acidified to pH 2.5 -3.0 with pepsin of pharmaceutical purity pepsin at 38 ⁰ C. It is then followed by flow washing using deionized water to the constant water conductivity value, centrifuging of the suspension followed by freezing the grit and its frost drying under under low pressure. The resulting pulp is filled in the packaging, hermetically sealed and sterilized by gamma radiation at a dose of 25kGy.

Example 2

The composite prepared by the procedure identical to example 1 is after its sterilization under aseptic conditions supplemented by the growth factor IGF-I in a quantity of 2.5 micrograms per one gram of the composite and by the secondary sodium phosphate in a quantity of 25 milligrams per gram of the composite to control pH. The resulting mixture is homogenized by stirring, filled in and hermetically sealed in containers.

Example 3

An example of the composite intended for use as a food supplement is the product prepared according to example 1, which is supplemented with vitamin C in quantity of 50 mg per one gram and by the complex of vitamin Bl in quantity of 7 mg per one gram of the product before filling, homogenized by stirring the mixture, filled in the packaging and hermetically sealed.