Comprehensive review of bacterial death mechanism on nanopillared nanostructured surfaces

Antibiotic resistance presents a significant global concern, worsened by overuse and limited development of new antibiotics. Medical implants, in particular, are increasingly susceptible to bacterial infections. To prevent biofilm formation on implants, it is essential to design specialized surface characteristics that either kill bacteria or inhibit their growth. Nanostructures resembling those found in nature, such as cicada wings, exhibit pronounced antibacterial efficacy. Drawing inspiration from these natural surfaces, artificial nanostructures made with similar features have demonstrated bactericidal effect. The bactericidal mechanism in nanostructures may seem simple, as the nanofeatures pierce through bacterial cells, leading to their death. However, research has shown that it is more complex and requires thorough investigation. Several studies indicate that while the bactericidal mechanism is initiated by mechanical contact, the precise killing process remains uncertain. Numerous experimental and theoretical investigations have aimed to elucidate the exact killing mechanism, yielding diverse conclusions and hypotheses, including cell death attributed to creep failure, motion-induced shear failure, apoptosis-induced programmed cell death and autolytic cell death, among others. This study undertakes a comprehensive review of all proposed death mechanisms. Moreover, it draws conclusions on the killing mechanism by meticulously analyzing the properties of bacterial membranes, their mechanosensing and adhesion mechanisms, energy-based models for bacterial adhesion, and experimental outcomes regarding the bactericidal efficacy of surfaces exhibiting diverse geometries.