Physiochemically Distinct Surface Properties of SU-8 Polymer Modulate Bacterial Cell-Surface Holdfast and Colonization.

SU-8 polymer is an excellent platform for diverse applications due to its high aspect ratio of micro/nanostructure fabrication and exceptional physicochemical and biocompatible properties. Although SU-8 polymer has often been investigated for various biological applications, how its surface properties influence the interaction of bacterial cells with the substrate and its colonization is poorly understood. In this work, we tailor SU-8 nanoscale surface properties to investigate single-cell motility, adhesion, and successive colonization of phytopathogenic bacteria, Xylella fastidiosa. Different surface properties of SU-8 thin films have been prepared using photolithography processing and oxygen plasma treatment. A more significant density of carboxyl groups in hydrophilic plasma-treated SU-8 surfaces promotes faster cell motility in the earlier growth stage. The hydrophobic nature of pristine SU-8 surfaces shows no trackable bacterial motility and 5-10 times more single cells adhered to the surface than its plasma-treated counterpart. In addition, plasma-treated SU-8 samples suppressed bacterial adhesion, with surfaces showing less than 5% coverage. These results not only showcase that SU-8 surface properties can impact the spatiotemporal bacterial behavior but also provide insights into pathogens' prominent ability to evolve and adapt to different surface properties.