The present invention describes a flat or improved flattened device to favor the implant of cells, that once it has been inserted in the subcutaneous tissue the device is coated by fibrocollagen, thus generating an immunologically privileged site inside the device, site which is useful as neovascularized reservoir for the implant of cells producers of biological factors, for the treatment of diseases such as diabetes mellitus, SNC or for the implant of primed cells against tumors.