Real-Time Imaging of the Mechanobactericidal Action of Colloidal Nanomaterials and Nanostructured Topographies

Mechanobactericidal nanomaterials, such as low-dimensional nanoparticles in suspension or high-aspect-ratio nanofabricated topographies, rely on their mechanical or physical interactions with bacteria and are promising antimicrobial strategies that overcome bacterial resistance to classical antibiotics. However, the underlying killing mechanisms are poorly understood, given the challenges associated with the real-time characterization of the mechanical interaction in a biologically relevant environment. Indeed, different death mechanisms have been proposed depending on the magnitude of the interaction forces. Herein, the real-time and single-cell response of bacteria to weak mechanical interactions with nanostructured topographies and "nanodarts," exemplified by flowing single-walled carbon nanotubes, is investigated. To that end, an advanced reporting strategy is used to follow sublethal physiological effects on bacteria upon contact with these materials. With this method, it is estimated that the contact time at which the initial stages of bacterial death occur is in the order of a few tens of minutes. This information contributes to a full understanding of the complex mechanisms of mechanically induced bacterial death.