Vascular prosthesis containing in the wall microcapsules, including hormoneproducing cells

Abstract: Vascular prostheses (1) of PTFE or of a low porosity material comprising an internal synthetic tubular mesh (1); microcapsules (2) made of saccharide and amino-acid polymers, containing hormone-­ producing cells, are placed between the prosthesis and the tubular mesh.

Description: Microcapsules consisting of saccharide, amino-acid polymers and other materials, such as agarose polymers, are already known and are apt to contain living hormone-producing cells. Microcapsules with the above-mentioned features are manufactured and marketed by Damon Biotech, Boston under the name of Encapcell, and also by other laboratories. Their features allow the protection of cells against possible rejection phenomena, their metabolic activity and the leaking out of the hormones secreted by the cells contained inside the microcapsules. However, the introduction of such microcapsules in the body brings about some problems, among which the following should be emphasized: 1) the microcapsules introduced in the body are wrapped in a reactive connective tissue, which prevents both the metabolic supply to the cells and the leaking out of the secreted hormones; 2) the microcapsules, if injected into a cavity such as the peritoneal cavity, tend to move downwards and concentrate in a limited area, thus causing a lively connective reaction involving them. Summary of the invention The problems of the prior technique can be solved through the use of a vascular prosthesis 1 of PTFE or of a low porosity material, inside of which another prosthesis 3 of a synthetic tubular mesh is used which allows oxygen and hormones to get through, since the microcapsules 2 of polysaccharide and amino-acid polymers or other semi-permeable materials, containing hormone-producing cells, are placed between the two prostheses. The preparation of the vascular prosthesis involves the following steps: a) Inside a vascular prosthesis 1 of PTFE or of a low posity mesh a second prosthesis 3 is placed, made of a synthetic tubular mesh with external support (EXS) is placed; b) the microcapsules 2 consisting of saccharide and amino-acid polymers and containing the hormone-producing cells are placed in the space between prosthesis 1 and prosthesis 3; c) a spindle 4 of a plastic material is then introduced in to prosthesis 3. Prostheses according to the present invention are used to create arter-venous fistulas. Detailed description of the invention The characteristics and advantages of the vascular prostheses and the relative preparation process, according to the present invention, will be dealt with in greater detail in the following description, also referring to the enclosed figure 1. Figure 1 represents schematically the prosthesis according to the present invention. With reference to the symbols of said figure, microcapsules 2, containing the hormone-producing cells, are placed between a prosthesis 1 of PTFE or of a low porosity material and a prosthesis 3 of a synthetic tubular mesh, and in said prosthesis 3 a plastic material spindle 4 is introduced. The tubular mesh is preferably made of polyester or polytetrafluoroethylene fibres (for example, Dacron or Teflon fibres) and has an internal diameter of between 4 and 14 mm with an external support (EXS). The empty spaces between the filaments making up such mesh are of between 10 and 300 micron, that is such as to retain the microcapsules. The microcapsules are made of saccharide and amino-acid polymers or other semi-permeable material with a porosity of about 60.000 Dalton, which allows the transfer of the metabolic products from the inside to the outside and viceversa, but not the passage of the immunoglobulins or other high molecular weight molecules. The spindle is preferably made of silastic or PVC and has an external diameter compatible with the internal diameter of prosthesis 3. The spindle transforms the space between prosthesis 1 and prosthesis 3, in which the microcapsules 2 will be placed, into a virtual space. The prosthesis according to the present invention is implanted, after extraction of the spindle into the recipient through an artero-venous fistula. A vascular prosthesis is thus obtained; consisting inside of a synthetic tubular mesh that retains the microcapsules, which are in practice exposed to the hematic flow and which is covered by an endothelium-like tissue. In such vascular prosthesis the hematic flow allows the metabolism of the cells contained in the microcapsules, and at the same time it also allows the circulation of the hormones secreted by the cells themselves. A particularly useful application is possible when the microcapsules contain Langherans islands cells which secrete insulin.

Claims: Vascular prosthesis consisting of a tubular element (1) of PTFE or of a low porosity material including in its interior another tubular element (3) of a synthetic mesh of polyester or polytetrafluoroethylene fibres with free spaces of between 10 and 300 micrometers which allows the passage of oxygen and hormones, microcapsules (2) consisting of polysaccharide and amino-acid polymers or of other semi-permeable materials and including hormone-producing cells being placed in the space between said tubular elements. Prosthesis according to claim 1, characterized in that said tubular element (3) has an internal diameter of between 4 and 14 mm. Process for the preparation of vascular prostheses containing in the wall microcapsules including hormone-producing cells, characterized in that: a) inside a tubular element (1) made of PTFE or of a low porosity material a second tubular element (3) is placed consisting of a synthetic mesh of polyester or polytetrafluoroethylene fibres with free spaces of between 10 and 300 micrometers; b) microcapsules (2) of polysaccharide and amino-acid polymers including hormone-producing cells are placed in the space between said tubular elements; c) a spindle (4) of silastic or PVC and having an external diameter compatible with the internal diameter of said tubular element (3) is introduced in the same tubular element (3).

Inventors: BROTZU GIOVANNI, CALAFIORE RICCARDO, BROTZU, GIOVANNI, CALAFIORE, RICCARDO
Applicants: BROTZU GIOVANNI, BROTZU, GIOVANNI
Application year: 1990
Main classification: A61L27
IPC codes: A61L27, A61F2, B01J13, A61K9