Deciphering the Roles of Interspace and Controlled Disorder in the Bactericidal Properties of Nanopatterns against Staphylococcus aureus

Abstract

Recent progress in nano-/micro-fabrication techniques has paved the way for the emergence of synthetic bactericidal patterned surfaces that are capable of killing the bacteria via mechanical mechanisms. Different design parameters are known to affect the bactericidal activity of nanopatterns. Evaluating the effects of each parameter, isolated from the others, requires systematic studies. Here, we systematically assessed the effects of the interspacing and disordered arrangement of nanopillars on the bactericidal properties of nanopatterned surfaces. Electron beam induced deposition (EBID) was used to additively manufacture nanopatterns with precisely controlled dimensions (i.e., a height of 190 nm, a diameter of 80 nm, and interspaces of 100, 170, 300, and 500 nm) as well as disordered versions of them. The killing efficiency of the nanopatterns against Gram-positive Staphylococcus aureus bacteria increased by decreasing the interspace, achieving the highest efficiency of 62 ± 23% on the nanopatterns with 100 nm interspacing. By comparison, the disordered nanopatterns did not influence the killing efficiency significantly, as compared to their ordered correspondents. Direct penetration of nanopatterns into the bacterial cell wall was identified as the killing mechanism according to cross-sectional views, which is consistent with previous studies. The findings indicate that future studies aimed at optimizing the design of nanopatterns should focus on the interspacing as an important parameter affecting the bactericidal properties. In combination with controlled disorder, nanopatterns with contrary effects on bacterial and mammalian cells may be developed.

Natural Architectures for Tissue Engineering and Regenerative Medicine

“…In line with this, another study identified that the killing efficiency of nanopillars (h: 190 nm, d: 80 nm) against Staphylococcus aureus bacteria increased by decreasing the interspace between the pillars [141]. Intriguingly, identical disordered nanopillars did not show a similar outcome [141]. Furthermore, multi-directional nanospikes (d: 120 nm, h; 300 nm, s: 200-400 nm) showed biocidal activity against both Staphylococcus aureus and Pseudomonas aeruginosa bacteria [142].…”

“…It was concluded that bacterial attachment becomes more disordered as spacing between pillars decreases, with increasing high-aspect-ratio being key in preventing bacterial attachment. In line with this, another study identified that the killing efficiency of nanopillars (h: 190 nm, d: 80 nm) against Staphylococcus aureus bacteria increased by decreasing the interspace between the pillars [141]. Intriguingly, identical disordered nanopillars did not show a similar outcome [141].…”

“…Another example of a natural surface able to modulate cell behaviour is the cicada wing, which is able to kill bacteria due to arrays of nanopillars present on its surface, as previously explained [85]. This bactericidal effect has led to the development of cicada inspired nanopatterned surfaces [36,141,142]. For instance, an array of nanopillars with a width of 70 nm, spacing of 100 nm, and a height of 210 nm ( Figure 9C) increased bacterial cell death compared to flat and larger nanopillared counterparts [36].…”

“…However, these properties are also relevant in guiding cell behaviour in vitro, which can be attributed to creating antifouling properties in vivo, for example. Concerning this, natural surfaces have been used in bioinspired approaches to guide cell behaviour, including spider silk [129,130], oyster shells (Pinctada maxima) [131][132][133][134][135], lotus leaves [136][137][138][139][140], and cicada and dragonfly wings [36,[141][142][143][144][145][146][147].…”

Recent Progress in Antimicrobial Nanomaterials

“…Evaluating the effects of each parameter, isolated from the others, requires systematic studies. A recent article has evaluated the influence of the interspacing and disordered arrangement of nanopillars on the bactericide properties of nanopatterned surfaces [ 35 ]. Electron beam induced deposition (EBID) was used to manufacture the nanopatterns with accurately controlled dimensions as well as disordered versions of them.…”