The present invention relates to nanoparticles comprising nucleic acids coated with a (biodegradable) polymer for reversible immobilization and/or controlled release of the nucleic acid comprising nanoparticles. Furthermore, the present invention is directed to medical or diagnostic devices, particularly stents and implants coated by a (biodegradable) polymer with the nucleic acid comprising nanoparticles for reversible immobilization and/or controlled release. Furthermore, the present invention is directed to the use of these nanoparticles coated with a (biodegradable) polymer and to the use of medical devices and implants coated by the (biodegradable) polymer with these nucleic acid comprising nanoparticles in the prophylactic or therapeutic treatment of diseases, particularly in the prevention or treatment of restenosis, calicification, foreign body reaction, or inflammation. Additionally, the present invention is directed to a method of preparing these nucleic acid comprising nanoparticles coated with a (biodegradable) polymer and to a method for coating nucleic acid comprising nanoparticles by a (biodegradable) polymer on medical or diagnostic devices.