Adhesion and Bactericidal Properties of a Wettability-Controlled Artificial Nanostructure

Abstract

The adhesion behavior and bactericidal properties of the nanostructured surface of Si nanopillar array, which mimicked a cicada wing surface, were evaluated using Escherichia coli. Wettability of the nanostructured surface was controlled by using self-assembled monolayer (SAM). The adhesion behavior was strongly dependent on the wettability of the surface and whether it was a nanostructured or a flat surface. The number of adhered cells on the nanostructured surface was higher than that on the flat Au surface. In addition, the cell membrane was more strongly damaged at a higher contact angle than at a lower contact angle on the nanostructured surface. Time-lapse imaging was used to analyze the changes in fluorescence intensity caused by the effusion of an intercellular fluid, including fluorescent protein (mCherry), at the single cell level on the cicada wing surface and the artificial nanostructured surface. We found that there were three stages of changes in the fluorescence intensity gradient.

Adhesion and bactericidal properties of nanostructured surfaces dependent on bacterial motility

“…On the bactericidal property test, the Si nano-pillar array substrate was fabricated and used as an articial nanostructure. Our group had reported that Si nano-pillar arrays could be obtained by colloidal lithography and metal-assisted chemical etching (MacEtch), 15,31 which allow controlling the nanopillar array dimensions. The gap of the nano-pillar was controlled by changing the diameter of PS beads.…”

“…Our group reported that the number of attached cells depended on presence or absence of nanostructure and the surface wettability. 15 The number of attached cells increased with the contact angle for water (WCA: water contact angle) and that on the nanostructured surface was about twice compared to the at surface at the same WCA. To develop an application in the eld of sanitary engineering, it is important to increase the number of attached cells to improve the bactericidal and antibacterial properties of the nanostructured surface.…”

“…Our group reported that the cicada wing surface caused the effusion of intercellular uid of Escherichia coli (E. coli) cells adhered to it. 15 To prove this, we measured the decrease in a uorescent protein expressed by E. coli, which indicated that the lysis of cells adhering to the nanostructure. The changes in uorescence intensity were classied into three stages: just trapped in the nanostructure, small effusion, and large effusion.…”

“…The bactericidal effect of the nanostructures was discovered by studying natural nanostructured surfaces such as cicada wings, [11][12][13][14][15] dragony wings, 12,16,17 and gecko ngers. 18,19 Later it was discovered that articial nanostructured surfaces composed of inorganic materials, such Si 11,15,20,21 and carbon nanotubes (CNT), 22 and organic materials, [23][24][25][26] also have bactericidal properties. The bactericidal activity on a nanostructure originates from its physical instead of from its chemical properties; the cell membranes are stretched by the nanostructured surface, which causes cell break.…”

“…It is possible to estimate cell death occurrence using commercially available DNA-staining reagents such as SYTO 9 and propidium iodide (PI), which indicate cell membrane damage. [11][12][13][14][15][16][17][18][19] This technology gives us information about cell membrane damage. It is noted that some population of bacteria inactivated by various methods such as UV and heat treatment to destroy micro-organisms can still survive as injured cells.…”