Self-Patterned Nanoscale Topography of Thin Copolymer Films Prepared by Evaporative Assembly-Resist Early-Stage Bacterial Adhesion

Biofilm formation on the surfaces of indwelling medical devices has become a growing health threat due to the development of antimicrobial resistance to infection-causing bacteria. For example, ventilator-associated pneumonia caused by Pseudomonas and Staphylococci species has become a significant concern in treatment of patients during COVID-19 pandemic. Nanostructured surfaces with antifouling activity are of interest as a promising strategy to prevent bacterial adhesion without triggering drug resistance. In this study, we report a facile evaporative approach to prepare block copolymer film coatings with nanoscale topography that resist bacterial adhesion. The initial attachment of the target bacterium Pseudomonas aeruginosa PAO1 to copolymer films as well as homopolymer films was evaluated by fluorescence microscopy. Significant reduction in bacterial adhesion (93-99% less) and area coverage (>92% less) on the copolymer films was observed compared with that on the control and homopolymer films [poly(methacrylic acid) (PMAA)-only 40 and 23% less, respectively]. The surfaces of poly(styrene)-PMAA copolymer films with patterned nanoscale topography that contains sharp peaks ranging from 20 to 80 nm spaced at 30-50 nm were confirmed by atomic force microscopy and the corresponding surface morphology analysis. Investigation of the surface wettability and surface potential of polymer films assists in understanding the effect of surface properties on the bacterial attachment. Comparison of bacterial growth studies in polymer solutions with the growth studies on coatings highlights the importance of physical nanostructure in resisting bacterial adhesion, as opposed to chemical characteristics of the copolymers. Such self-patterned antifouling surface coatings, produced with a straightforward and energy-efficient approach, could provide a convenient and effective method to resist bacterial fouling on the surface of medical devices and reduce device-associated infections.