A porous matrix based on a biocompatible polymer or polymer mixture comprising pores of size 150 Microm or below and also pores of size 300 Microm or above, where the degree of porosity of the matrix is 93-98 %, is new. Independent claims are also included for: (1) production of a porous matrix based on a biodegradable polymer (mixture) by compacting a mixture of polymer particles of size 20-950 (especially 108-250) Microm and cooking salt of particle size 90-670 (especially 250-425) Microm and then dissolving out the salt； (2) production of a porous matrix based on a biocompatible polymer (mixture) by compacting a mixture of polymer particles, a pore-former and polymer solution and then dissolving out the pore-former； (3) implants comprising the matrices and cells, the cells being of >；=2 types, one type being hepatocytes and another being Langerhans islets； and (4) a cell recovery process for the inoculation of implantable matrices comprising removing a piece of tissue, treating the piece with sodium chloride, potassium chloride, HEPES, calcium chloride, collagenase and trypsin inhibitor at pH 7.3-7.4, optionally freshening the tissue piece and then shaking it in a suitable medium and recovering the resulting cell suspension.
