An element provided with a layer based on fibrin- or fibrinogen-containing material, said element comprising (a) a hydrophobic or substantially hydrophobic support, which has a porous part with a thickness of 0.1 to 5 mm, and whose pores, extending across its thickness have a node spacing of 5 to 100 .mu.m, one face of said porous part being treated with a compound based on fibrin and/or a fibrinogen-containing material, and (b) a fibrin-based layer covering said treated surface of the support, characterized in that said fibrin-based layer is substantially uniform and homogeneous on said treated surface, and that the fibrin layer and at least the face of the support in contact with the fibrin layer are substantially free of fibrinogen.