A Coating that Combines Lotus-Effect and Contact-Active Antimicrobial Properties on Silicone

The antimicrobial equipment of materials is of great importance in medicine but also in daily life. A challenge is the antimicrobial modification of hydrophobic surfaces without increasing their low surface energy. This is particularly important for silicone-based materials. Because most antimicrobial surface modifications render the materials more hydrophilic, methods are needed to achieve antimicrobial activity without changing the high water-contact-angle. This is achieved in the present work, where SiO2 nanoparticles are prepared and functionalized with 3-(trimethoxysilyl)-propyldimethyloctadecyl ammonium chloride (QAS) in a one-pot synthesis. The modified nanoparticles are applied onto a silicone surface from suspension with no need of elaborate pretreatment. The resulting surface exhibits a Lotus-Effect combined with contact-active antimicrobial properties. The particle surfaces show self-organizing micro- and nanostructures that afford a water-contact angle of 144 degrees and a hysteresis below 10 degrees. The particles are self-adhering on the silicone after solvent evaporation and resistant against immersion into and washing with water for at least 5 d. Thereby, the adhesion of the bacterial strain Staphylococcus aureus to these surfaces is reduced and the remaining bacterial cells are killed within 16 h. This is the first example of a Lotus-Effect surface with intrinsic contact-active antimicrobial properties.