Antibacterial effects of nano-imprinted moth-eye film in practical settings

Abstract

BackgroundRecent studies report that surfaces displaying micrometer- or nanometer-sized undulating structures exhibit antibacterial effects. In previous work, we described the use of an advanced nanofabrication technique to generate an artificial biomimetic Moth-eye film by coating a polyethylene terephthalate (PET) film with nanoscale moth-eye protrusions made from a hydrophilic resin. This moth-eye film exhibited enhanced antibacterial effects in in vitro experiments. The aim of the present study was to verify the antibacterial efficacy of the Moth-eye film in practical environments.Materials and methodsThe antibacterial effects of three types of film (Moth-eye film, Flat film, and PET film) were compared. Sample films were pasted onto hand washing basins at the testing locations. After several hours, bacteria were collected from the surface of the sample films with one of three kinds of culture media stamper (to permit identification of bacterial species). The stampers were incubated for 48 hours at 35°C, and the numbers of colonies were counted.Results and discussionThe number of common bacteria including E. coli and S. aureus obtained from the Moth-eye film was significantly lower than those from the PET film (p<0.05) and Flat film at 1 hour (p<0.05). This study found that the Moth-eye film showed a long-term (6h) antibacterial effect and the Moth-eye structure (PET coated with nanoscale cone-shaped pillars) demonstrated a physical antibacterial effect from earlier time points. Therefore, the Moth-eye film appears to have potential general-purpose applications in practical environments.

Simple Fabrication of Transparent, Colorless, and Self-Disinfecting Polyethylene Terephthalate Film via Cold Plasma Treatment

“…Despite its lower stiffness (Young's modulus) than that of metals and ceramics, polymers including PET, polyethylene, and polyvinyl chloride may achieve an antibacterial function through modifications to their surface morphology. For example, PET (200 nm in height and pitch) [25] and PMMA (70-215 nm diameter, 200-300 nm height) [26] nanopillar surfaces fabricated using nanoimprint lithography showed lethal action against Staphylococcus and coliform bacteria.…”

“…As well as plasma-etching techniques, nanostructuring techniques for antibacterial surfaces have been studied: nanoimprint lithography [25,26], anodization [48], thermal oxidation [57], electron-beam oxidation [58], hydrothermal etching [57], and electrodeposition [46]. Titanium randomly-oriented nanopillar arrays (40.3 nm diameter) fabricated using hydrothermal etching showed high antibacterial activity against P. aeruginosa but low antibacterial activity against S. aureus [46].…”

“…Compared to stiff materials (e.g., silicon [7], graphene [8], diamond [9], graphene oxide [11], titanium [12], or titanium oxide [13]), soft polymers have received relatively little study for use in antibacterial nanostructured surfaces through biophysical interactions with the bacterial membrane [19,[23][24][25][26][27]. Some studies have found that the antibacterial activity of polyethylene terephthalate (PET) films was enhanced when the physical bactericidal mechanism was activated by modifying the surface structures via cold oxygen plasma [23,24] and nanoimprint lithography [19,25] treatments. Plasma treatment, often used for dry-etching using energetic atoms or molecules, is a useful technique for heat-sensitive materials such as polymers.…”

Adhesion and bactericidal properties of nanostructured surfaces dependent on bacterial motility

“…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.…”

Exploring the potential of polyethylene terephthalate in the design of antibacterial surfaces

“…The combination of topographical modification and coatings has been reported to increase its effectiveness. For instance, Yamada et al [42] coated a PET film with nanoscale moth-eye cone-shaped protrusions from a hydrophilic resin made of urethane acrylate and polyethylene glycol (PEG) derivatives [43] with a size of approximately 200 nm in depth and diameter. Bacteria counts were reduced significantly with the use of moth-eye film compared to uncoated PET substrate due to specific structure of motheye film.…”