The present invention relates to a sheet or tubular structure consisting of biocompatible material, which is elastic and comprises at least one biologically active substance in at least one region and to a sheet or tubular structure, which comprises at least one biologically active substance release-modifying agent in at least one region as well as an implant covered at least partially by the sheet or tubular structure of the invention. The present invention further provides a method and an apparatus for producing, and preferably customizing and/or optimizing, the sheet or tubular structure of the invention. The sheet or tubular structure of the invention can be customized/optimized before implantation in the operating room.