WO2004091678A1

WO2004091678A1 - Chitosan film used as a periosteum replacement

Info

Publication number: WO2004091678A1
Application number: PCT/EP2004/004073
Authority: WO
Inventors: Andrea Pahmeier; Birger Hahnemann; Thomas LÖTZBEYER; Philipp Sperling
Original assignee: Fti Technologies Gmbh
Priority date: 2003-04-16
Filing date: 2004-04-16
Publication date: 2004-10-28
Also published as: DE10317578A1

Abstract

The invention relates to the use of a biocompatible material, for example as a flexible film and/or porous matrix, said material being based on chitosan and an acid. The material is used as a medium in the orthopaedic field, in particular as a periosteum replacement.

Description

C itosan film as a periosteal replacement

description

The invention relates to the use of a biocompatible material based on chitosan and an acid, e.g. as a flexible film and / or porous matrix, as an agent in the field of orthopedics, in particular as a periosteal replacement.

German patent application 199 48 120.2 discloses a process for producing a biocompatible three-dimensional matrix, in which an aqueous solution of a chitosan and an acid present in excess, in particular a hydroxycarboxylic acid, is frozen and the water is sublimed under reduced pressure, the excess acid before the Freeze or removed after sublimation of the water, in particular neutralized. Furthermore, a matrix obtainable by the method is disclosed which can be used for the production of implants. - - -

German patent application 101 17 234.6 discloses biocompatible non-porous materials based on chitosan and an acid, in particular a hydroxycarboxylic acid. These materials can be in the form of a film, for example.

Based on this finding, it was the object of the present invention to provide new applications for materials based on chitosan and an acid, in particular a hydroxycarboxylic acid.

A first aspect of the present invention therefore relates to the use of a biocompatible material based on chitosan and an acid, in particular a hydroxycarboxylic acid, as an agent in the field of orthopedics, for example as a replacement for the periosteum.

In a first embodiment, the material is in the form of a flexible, in particular non-porous, film. The film has a thickness of less than or equal to approximately 5 mm, for example between 0.1 μm and 1 mm, preferably 1 μm to 200 μm, particularly preferably approximately 50 μm to 100 μm, and is obtainable from:

Provision of an aqueous solution of a chitosan and an excess acid, in particular one

hydroxy,

Drying the solution without freezing and

Remove excess acids before or / and after

Drying, preferably by neutralization.

The film can be produced in prefabricated strips with a width of, for example, 1 mm - 10 mm. Alternatively, the required pieces of foil can also as required, ie in each case by the extent of the damage and the size ^"of the ^'lesion ZTB. During einerOperatiön be made. For this ^purpose,' the film can appropriately or slightly larger than required and tailored by gluing or sewing on the damage site.

The foils can have a smooth surface. Alternatively, a film with a surface structured on both sides can also be used. In a preferred embodiment, the film contains one or more knobs which have a diameter of, for example, 0.1 cm to 2 cm, in particular 0.5 cm to 1.5 cm and particularly preferably approximately 1 cm and a height of, for example, 0.1 mm up to 5 mm, preferably 0.2 mm to 2 mm. A film with a structured surface can be produced by pouring the material into an appropriate shape. One area of application of the film is the use as a periosteal replacement, for example for surgical interventions on joints, in particular for knee operations. It has also been found that the use of the film according to the invention promotes the healing process and the formation of cartilage in cartilage defects. The film can adapt to the given conditions and is also sewable. Under these conditions, chondrocytes, for example human chondrocytes, show a significantly better reproduction than in other matrices.

The film can be used as a support for a porous three-dimensional matrix. Thus, biocompatible composite materials can be provided which comprise at least one biocompatible film, as described above, and at least one biocompatible porous matrix. The biocompatible porous matrix is preferably based on chitosan and an acid, in particular a hydroxycarboxylic acid. However, other porous biocompatible matrices can also be used.

In a ^' further preferred ^' embodiment, the biocompatible material based on chitosan and an acid is a porous matrix.

A biocompatible porous matrix according to German application 199 48 1 20.2 is particularly preferably used, which is obtainable by:

Providing an aqueous solution of a chitosan and an im

Excess acid present, especially a hydroxycarboxylic acid,

Freezing and drying the solution, in particular by sublimation under reduced pressure and

Removal of excess acid before or / and after freezing, in particular by neutralization with a suitable base, for example NaOH. The porous matrix can be used, for example, as a matrix for cells in medical or veterinary applications. It has been found that the porous matrix is particularly well suited for the ingrowth of chondrocytes. The chondrocytes can also be grown on the matrix, for example. Such an increase can take place over a period of a few days to several weeks.

The porous matrix can be produced in prefabricated pieces with a volume of, for example, 1 -1 O mm ³ . Alternatively, the required pieces can be made as needed, for example during an operation. For this purpose, the matrix can be cut to size and attached to the damaged area by gluing or sewing.

In a further embodiment, the material can be a combination of a flexible film and a porous matrix. The film and the matrix can be used as separate components, for example for the reconstruction of cartilage tissue. An example of such a combination of materials, in which the film and matrix are used as separate components, is shown in Figure 1. According to Figure 1, a porous matrix (3) is inserted at the site of the cartilage lesion (1, 2), which may be populated with chondrocytes. A film (4) is used as a cover. The film (4) can be coated with a suitable adhesive, e.g. a fibrin glue or a tissue glue, can be fixed or sewn.

In an analogous manner as shown in Figure 1, arthrotonic or arthroscopic surgery on the knee for the treatment of cartilage defects, for example an autologous chondrocyte implantation, can be carried out. For this purpose, the defect is curetted and, if necessary, a porous matrix populated with chondrocytes is precisely fitted. Instead of a matrix, sponges populated with chondrocytes can also be used one. other suitable material can be used. It is also possible to implant cells sewn into a sachet, the sachet preferably consisting of the matrix or film according to the invention. Alternatively, spheroids can also be injected under the matrix. The graft is fixed either by gluing or by suturing. Then the film according to the invention is covered.

The use of the films according to the invention instead of periosteal tissue offers many advantages. First, there is no need for a second incision on the patient, which is necessary to remove the periosteal tissue, as well as the time-consuming and time-consuming preparation of the periosteum. In addition, the film according to the invention can be easily provided in constant quality and in the required size. The covering with the film ensures a stable anchoring of the transplanted cells at the site of the lesion and also promotes the healing process.

^"" Another preferred application of the film ^" relates to use as a biohybrid implant, for example as a capsule or tube structure, optionally in combination with the porous matrix for encapsulating cells, in particular chondrocytes. In one embodiment, a shell consisting of the film, for example in the form of a sack or a tubular structure into which chondrocytes are filled in. The sheath is implanted at the site of the joint lesion and can, for example, promote cartilage formation.

Furthermore, the chitosan-based material, in particular the film, can serve as a covering of tissue, for example cartilage tissue or periosteal tissue, after injuries and / or during surgical interventions. The non-porous film according to the invention, the porous matrix or a composite system based thereon can also be used for the in vitro cultivation of chondrocytes. The materials can contain additional factors for cell growth, such as cytokines.

The porous matrix can optionally have anisotropic structures, for example fibers or / and chambers aligned in parallel. The anisotropic matrix is available through:

Providing an aqueous solution of a chitosan and an excess acid, especially one

Hydroxycarboxylic acid, anisotropic freezing and drying of the solution, in particular by

Sublimation at reduced pressure and

Remove excess acid before or / and after freezing.

The anisotropic freezing preferably comprises freezing using structured cooling elements, e.g. Tubes in direct or indirect contact with the matrix during the freezing process. The cooling elements can be elongated, for example in order to obtain fibers or chambers in the matrix which are aligned in parallel. However, curved structures, e.g. Replicas of the organ to be molded can be used as cooling elements.

The anisotropic porous matrix can be used in a biocompatible composite material system together with another material, for example with a biocompatible non-porous film. The anisotropic matrix or the composite material system based thereon can be used for the in vitro cultivation of cells, for example chondrocytes, or as an implant without prior cell colonization, in accordance with the aforementioned applications. The matrices and films according to the invention based on chitosan and acids are essentially produced by the process specified in German applications 1 99 48 1 20.2 and 101 1 7 234.6, unless stated otherwise. An aqueous solution of a partially deacetylated chitosan and an acid present in excess is preferably prepared first. Excess is understood to mean that the pH of the aqueous solution is acidic, preferably below pH <4. As a result, the free amino groups of the chitosan are at least partially protonated, which increases the solubility in water. The amount of acid is not critical. It only has to be chosen so that the chitosan goes into solution. Excessive acid addition is avoided if possible, since excess acid has to be removed again, and this makes processing with large amounts of acid more difficult. Amounts of acid which give a 0.05 to 1 N, preferably 0.1 to 0.5 N, in particular 0.1 to 0.3 N solution are favorable. The amount of chitosan is preferably chosen so that a 0.01 to 0.5 M, preferably 0.1 to 0.3 M solution results. The concentration of the chitosan solution can influence the structure of the matrix, in particular its pore size. In this way, the pore size of the matrix can be matched to the particular cell type with which the matrix is to be populated.

Chitosan does not have a uniform molecular weight due to its production from natural sources. Depending on the source and processing method, the molecular weight can be between 20 kDa and over 1000 kDa.

The chitosan is not subject to any restrictions in terms of its molecular weight for the production of the three-dimensional matrix. An acid, which is an inorganic acid or preferably an organic acid, particularly preferably an alkyl or aryl, is used for the preparation of the aqueous chitosan solution. Hyd roxycarboxylic acid. Hydroxycarboxylic acids with 2 to 12 carbon atoms are particularly suitable, it being possible for one or more hydroxyl groups and one or more carboxyl groups to be present in the molecule. Specific examples are glycolic acid, lactic acid, malic acid, tartaric acid, citric acid and mandelic acid. Lactic acid is particularly preferred.

When producing a porous matrix, the solution of chitosan and acid is first at least partially neutralized by adding base and then frozen or directly frozen without prior neutralization. Neutralization before freezing is preferred. The pH after neutralization is generally 5.0 to 7.5, preferably 5.5 to 7.0 and in particular 6.0 to 7.0.

After freezing, the water is sublimed under reduced pressure, for example in the pressure range from 0.001 to 3 hPa.

To produce a non-porous film, the solution is not frozen and sublimed, but rather is dried without freezing at an optionally elevated temperature and / or reduced pressure and preferably neutralized after drying. The resulting non-porous matrix is strong and stretchy when wet.

Due to the large number of amino and hydroxy groups, the material can be modified as required. In a preferred embodiment, ligands are covalently or non-covalently bound to the chitosan, preferably to the free amino groups of the chitosan. As ligands z. B. growth substances, proteins, hormones, heparin, heparan sulfates, chondroite sulfates, dextran sulfates or a mixture of these substances can be used. The ligands are preferably used to control and improve cell proliferation. The cell growth on the matrix or the film is further improved if the matrix is coated with autologous fibrin.

The three-dimensional matrix can be connected to eukaryotic cells, e.g. can be colonized with human or with animal cells (for example from horses, dogs or sharks). Shark cells are particularly suitable because they do not trigger an essential immunological response in the recipient.

The materials, as described above, can be used in human medicine and veterinary medicine, in particular in orthopedic interventions on bones and joints.

The materials are sterilized before use in cell culture to guarantee sterility. The sterilization can be carried out by temperature treatment, e.g. by autoclaving, steam treatment etc. or / and by radiation, e.g. Gamma radiation treatment. Preferably the sterilization is carried out in a physiologically acceptable buffered solution, e.g. in PBS to ensure complete wetting of the matrix -bz-w- of the film with liquid - and- to ensure the absence of larger air pockets.

When the cells are cultivated, the material is broken down in a period of about 5-8 weeks or longer. The breakdown times can be adjusted via the degree of deacetylation of the chitosan and the concentration of the material.

The invention is further illustrated by the following figures and examples. Explanation of the pictures:

Figure 1 shows a combination of materials in which foil and matrix are used as separate combinations.

Figures 2 to 8 show the use of a film according to the invention in knee surgery. Figure 2 shows a deep cartilage defect in a bovine knee. Figure 3 shows the support of a film according to the invention with a thickness of 70 μm as a periosteroid. The process of sewing the film is shown in Figures 4 to 6. Figure 7 shows the completely sewn film. The filling of the defect, for example with spheroids, can be seen in Figure 8 by injection under the film.

Examples

Example 1: Production of a non-porous film

In accordance with the process described in Example 3 of DE 199-48 1 20.2, a mixture of chitosan and lactic acid is produced. The solution is poured into a petri dish, dried at 50 ° C. and, after the formation of a crystal-clear film, neutralized to a pH of 7 with 1 M sodium hydroxide solution. The resulting film is strong and stretchy when wet.

By adding the sodium hydroxide solution from one side, a film with a "memory effect" can be created. Example 2: In vitro cultivation of chondrocytes

Chondrocytes were applied to the film or to the matrix and grown in vitro. Chondrocytes can be grown in the matrix particularly with pore diameters of approximately 20 μm to 100 μm.

Claims

Expectations

1 . Use of a biocompatible material based on chitosan and an acid as an agent in the field of orthopedics.

2. Use according to claim 1 as a perioster set.

3. Use according to one of claims 1 or 2, characterized in that the material is in the form of a flexible, in particular non-porous, film.

4. Use according to claim 3, characterized in that the film has nubs.

5. Use according to any one of claims 1 or 2, characterized dadurcrr _"that the material is in the form of a porous matrix.

6. Use according to one of claims 1 to 5, characterized in that the material is present as a combination of a flexible film and a porous matrix.

7. Use according to claim 6, characterized in that the film and matrix are used as separate components.

8. Use according to claim 6, characterized in that the film and matrix are used as the composite component.

9. Use according to one of the preceding claims for the growth of chondrocytes.

1 0. Use according to any one of the preceding claims, characterized in that the material has a thickness in the range from 0.1 μm to 5 mm.

1 1. Use of a biocompatible material based on chitosan and an acid as a means of repairing cartilage tissue.

1 2. Use of a biocompatible material based on chitosan and an acid as a sponge for colonization with chondrocytes.

1 3. Use of a biocompatible material based on chitosan and an acid as a sachet into which cells can be sewn.

1 4. Use of a biocompatible material based on chitosan and an acid to cover bones and joints after

Injuries and / or during surgery.