Revealing the Mechanical Impact of Biomimetic Nanostructures on Bacterial Behavior

Naturally inspired nanostructured surfaces, by mechanically inhibiting bacterial adhesion or killing bacteria, effectively prevent the emergence of antibiotic resistance, making them a promising strategy against healthcare-associated infections. However, the current mechanical antibacterial mechanism of nanostructures is not clear, thus limiting their potential application in medical devices. This work mainly investigates the mechanical influence mechanism of biomimetic nanostructure parameters on bacterial adhesion and growth status. The results of 12 h bacterial culture showed that compared to flat surfaces, nanostructures reduced the adhesion of both E. coli and S. aureus bacteria by 49%~82%. The bactericidal efficiency against E. coli increased by 5.5%~31%, depending on the shape of the nanostructures. Nanostructures with smaller tip diameters exhibited the best anti-bacterial adhesion effects. Nanostructures with sharp tips and larger interspaces showed greater bactericidal effects against E. coli. Surfaces with larger tip diameters had the poorest antibacterial effects. Subsequently, a finite element model was established to quantitatively analyze the mechanical interactions between bacteria and nanostructures. It was found that different nanostructures affect bacterial adhesion and growth by altering the contact area with bacteria and inducing stress and deformation on the cell wall. Nanostructures with smaller tip diameters reduced the attachment area to bacteria, thereby reducing bacterial adhesion strength. Nanostructures with larger interspaces induced greater stress and deformation on the cell wall, thereby enhancing bactericidal efficiency. Finally, experimental verification with L929 cells confirmed that nanostructures do not cause mechanical damage to the cells. These studies deepen our understanding of the antibacterial mechanism of biomimetic nanostructures and provide new insights for the design of optimal nanostructures.