Antibacterial properties of nanostructured surfaces via the self-assembly of block copolymers: (II) Effects of surface morphology

The adhesion of unwanted pathogenic bacteria creates a great challenge and health risks when designing implantable medical devices. In response, significant efforts have been made to design effective antibacterial surface coatings. Antibacterial surfaces are typically based on liquid- repellent or bactericidal properties. However, either single property alone has a disadvantage in practical applications. Therefore, the development of dual-functional surface coatings is needed but is still challenging due to the different mechanisms underlying the respective functions. Here we develop synergistic surfaces combining bacteria-releasing and bactericidal properties against Escherichia coli (a Gram-negative bacterium) and Listeria monocytogenes (a Gram-positive bacterium). Hexagonally packed vertically oriented cylindrical polystyrene structures are fabricated via the self-assembly of polystyrene-block-poly(methyl methacrylate) diblock copolymers on silicon substrates. How the surface morphology (lamella and cylinder) and the domain size affect the bacteria-releasing and bactericidal properties are investigated. The results demonstrate that the cylindrical nanostructures show higher efficacy, and there is a critical domain size at which the dual properties emerge.