Complex medical devices like endoscopes are very difficult to sterilize, due to the use of different materials for their construction and to complex device geometries that are difficult to process using liquid sterilants. The use of materials like metals, polymers and glasses requires the adoption of sterilization techniques characterized by reduced thermal and mechanical energy. In this work patents on medical devices sterilization have been reported. Then, we focused our attention on the fact that structured surfaces formed by micro- or nano- spaces suggest the use of gas-like processes characterized by reduced surface tension and improved mass transfer, like the supercritical fluids. Therefore, patented techniques based on the use of supercritical CO2 (SC-CO2) have been studied, indicating the possible mechanism of microorganism inactivation; then, due to some limitations of SC-CO2 action, the addition of small quantities of other compounds, like carboxylic acids, hydrogen peroxide and in general oxidative or non-oxidative additives, has been patented. These approaches have been reviewed, together with a new sterilization concept based on the modification of acetic and peracetic acid by the addition of SC-CO2, producing expanded liquid single phase mixtures, whose action can be modulated for the sterilization of micro-structured and delicate medical instruments.