Nanoscale Surface Properties of SU-8 Polymer Modulate Xylella fastidiosa Motility, Adhesion and Colonization

SU-8 polymer is an excellent platform for fabrication of many health care devices due to the easy fabrication of high aspect ratio micro/nanostructure and exceptional optical, chemical, and biocompatible properties of this material. In this work, we modify SU-8 surface properties to investigate their role in single cell motility and adhesion of the phytopathogen <i>Xylella fastidiosa</i>. Different SU-8 samples have been prepared using photolithography processing, and oxygen plasma treatment. We found a significant difference in bacterial cell motility, adhesion, and subsequent colonization on SU-8 as nanoscale surface property changes. The mean velocity and displacement of single cells have been extracted from cell tracking information and the size and quantity of microcolonies are compared for different samples. A larger density of carboxyl groups in hydrophilic plasma-treated SU-8 surfaces promotes faster cell motility in early growth stages. The hydrophobic, pristine SU-8 surfaces present no bacterial motility and 10 times more adhered single cells than plasma-treated SU-8 surfaces, which on their turn suppressed bacterial growth, showing less than 5% bacterial coverage. These results showcase that SU-8 surface properties can impact the bacterial behavior in a spatiotemporal manner, and could be used to design novel strategies and devices for signal transduction and antimicrobial applications.