Nanowire Arrays as Force Sensors with Super-Resolved Localization Position Detection: Application to Optical Measurement of Bacterial Adhesion Forces

The design and application of indium phosphide (InP) nanowire arrays to acquire Xylella fastidiosa bacterial cell vector force maps are discussed. The nanowire deflections are measured with subdiffraction localization confocal laser scanning microscopy (CLSM). The nanowire mechanical stability in air and liquid media as well as methods to average out thermally induced oscillations are investigated. The accuracy of center determination of the CLSM reflected laser intensity profile at nanowire apex is studied using Gaussian fitting and localization microscopy techniques. These results show that the method is reliable for measuring nanowire displacements above approximate to 25 nm. Corresponding force ranges probed by this method can be customized depending on nanowire geometry and array configuration. The method is applied to explore X. fastidiosa cell adhesion forces on the InP nanowire surface, and in situ probes the effect of N-acetylcysteine on adhered cells. Future perspectives for application of this method in microbiology studies are also outlined.