White Light-Activated Antimicrobial Paint using Crystal Violet

Crystal violet (CV) was incorporated into acrylic latex to produce white-light-activated antimicrobial paint (WLAAP). Measurement of the water contact angle of the WLAAP showed that the water contact angle increased with increasing CV concentration. In a leaching test over 120 h, the amount of CV that leached from the WLAAPs was close to the detection limit (<0.03%). The WLAAPs were used to coat samples of polyurethane, and these showed bactericidal activity against Escherichia coli, which is a key causative agent of healthcare-associated infections (HAIs). A reduction in the numbers of viable bacteria was observed on the painted coated polyurethane after 6 h in the dark, and the bactericidal activity increased with increasing CV concentration (<i>P</i> < 0.1). After 6 h of white light exposure, all of coated polyurethanes demonstrated a potent photobactericidal activity, and it was statistically confirmed that the WLAAP showed better activity in white light than in the dark (<i>P</i> < 0.05). At the highest CV concentration, the numbers of viable bacteria fell below the detection limit (<10³ CFU/mL) after 6 h of white light exposure. The difference in antimicrobial activity between the materials in the light and dark was 0.48 log at CV 250 ppm, and it increased by 0.43 log at each increment of CV 250 ppm. The difference was the highest (>1.8 log) at the highest CV concentration (1000 ppm). These WLAAPs are promising candidates for use in healthcare facilities to reduce HAIs

Superhydrophobic and White Light-Activated Bactericidal Surface through a Simple Coating

Bacterial adhesion and proliferation on surfaces are a challenge in medical and industrial fields. Here, a simple one-step technique is reported to fabricate self-cleaning and bactericidal surfaces. White, blue, and violet paints were produced using titanium dioxide nanoparticles, 1<i>H</i>,1<i>H</i>,2<i>H</i>,2<i>H</i>-perfluorooctyltriethoxysilane, crystal violet, toluidine Blue O, and ethanol solution. All of the painted surfaces showed superhydrophobicity in air, and even after hexadecane oil contamination, they retained water repellency and self-cleaning properties. In an assay of bacterial adhesion, significant reductions (>99.8%) in the number of adherent bacteria were observed for all the painted surfaces. In bactericidal tests, the painted surfaces not only demonstrated bactericidal activity against <i>Staphylococcus aureus</i> and <i>Escherichia coli</i> in the dark but also induced very potent photosensitization (>4.4 log reduction in the number of viable bacteria on the violet painted surface) under white light illumination. The technique that we developed here is general and can be used on a wide range of substrates such as paper, glass, polymers, and others

The Anti-Biofouling Properties of Superhydrophobic Surfaces are Short-Lived

Superhydrophobic surfaces are present in nature on the leaves of many plant species. Water rolls on these surfaces, and the rolling motion picks up particles including bacteria and viruses. Man-made superhydrophobic surfaces have been made in an effort to reduce biofouling. We show here that the anti-biofouling property of a superhydrophobic surface is due to an entrapped air-bubble layer that reduces contact between the bacteria and the surface. Further, we showed that prolonged immersion of superhydrophobic surfaces in water led to loss of the bubble-layer and subsequent bacterial adhesion that unexpectedly exceeded that of the control materials. This behavior was not restricted to one particular type of material but was evident on different types of superhydrophobic surfaces. This work is important in that it suggests that superhydrophobic surfaces may actually encourage bacterial adhesion during longer term exposure

The Anti-Biofouling Properties of Superhydrophobic Surfaces are Short-Lived

Superhydrophobic surfaces are present in nature on the leaves of many plant species. Water rolls on these surfaces, and the rolling motion picks up particles including bacteria and viruses. Man-made superhydrophobic surfaces have been made in an effort to reduce biofouling. We show here that the anti-biofouling property of a superhydrophobic surface is due to an entrapped air-bubble layer that reduces contact between the bacteria and the surface. Further, we showed that prolonged immersion of superhydrophobic surfaces in water led to loss of the bubble-layer and subsequent bacterial adhesion that unexpectedly exceeded that of the control materials. This behavior was not restricted to one particular type of material but was evident on different types of superhydrophobic surfaces. This work is important in that it suggests that superhydrophobic surfaces may actually encourage bacterial adhesion during longer term exposure

Antimicrobial Air Filters Using Natural <i>Euscaphis japonica</i> Nanoparticles

<div><p>Controlling bioaerosols has become more important with increasing participation in indoor activities. Treatments using natural-product nanomaterials are a promising technique because of their relatively low toxicity compared to inorganic nanomaterials such as silver nanoparticles or carbon nanotubes. In this study, antimicrobial filters were fabricated from natural <i>Euscaphis japonica</i> nanoparticles, which were produced by nebulizing <i>E</i>. <i>japonica</i> extract. The coated filters were assessed in terms of pressure drop, antimicrobial activity, filtration efficiency, major chemical components, and cytotoxicity. Pressure drop and antimicrobial activity increased as a function of nanoparticle deposition time (590, 855, and 1150 µg/cm2_filter at 3-, 6-, and 9-min depositions, respectively). In filter tests, the antimicrobial efficacy was greater against <i>Staphylococcus epidermidis</i> than <i>Micrococcus luteus</i>; ~61, ~73, and ~82% of <i>M</i>. <i>luteus</i> cells were inactivated on filters that had been coated for 3, 6, and 9 min, respectively, while the corresponding values were ~78, ~88, and ~94% with <i>S</i>. <i>epidermidis</i>. Although statistically significant differences in filtration performance were not observed between samples as a function of deposition time, the average filtration efficacy was slightly higher for <i>S</i>. <i>epidermidis</i> aerosols (~97%) than for <i>M</i>. <i>luteus</i> aerosols (~95%). High-performance liquid chromatography (HPLC) and electrospray ionization-tandem mass spectrometry (ESI/MS) analyses confirmed that the major chemical compounds in the <i>E</i>. <i>japonica</i> extract were 1(ß)-<i>O</i>-galloyl pedunculagin, quercetin-3-<i>O</i>-glucuronide, and kaempferol-3-<i>O</i>-glucoside. <i>In vitro</i> cytotoxicity and disk diffusion tests showed that <i>E</i>. <i>japonica</i> nanoparticles were less toxic and exhibited stronger antimicrobial activity toward some bacterial strains than a reference soluble nickel compound, which is classified as a human carcinogen. This study provides valuable information for the development of a bioaerosol control system that is environmental friendly and suitable for use in indoor environments.</p></div

The inactivation rate of <i>E</i>. <i>japonica</i> extract nanoparticles-coated filters on bacterial aerosols.

<p>Error bars indicate standard deviations (<i>n</i> = 3).</p

Concentrations, GSD, GMD, and peak diameters of test bacterial bioaerosols (<i>n</i> = 3).

<p>¹GSD, geometric standard deviation.</p><p>²GMD, geometric mean diameter.</p><p>Concentrations, GSD, GMD, and peak diameters of test bacterial bioaerosols (<i>n</i> = 3).</p

The inhibitory effects of <i>E</i>. <i>japonica</i> and a soluble nickel compound (SNC) on A549 cancer and HEL 299 cells.

<p>Error bars indicate standard deviations (<i>n</i> = 10) ¹Half maximal inhibitory concentration, ²A549 human lung adenocarcinoma cancer cells, ³HEL 299 human lung fibroblast cells.</p

The pressure drop through the antimicrobial air filters is shown as a function of particle deposition conditions.

<p>Error bars indicate standard deviations (<i>n</i> = 3).</p

A comparison of the antimicrobial activity of <i>E</i>. <i>japonica</i> and SNC using the disk diffusion method (<i>n</i> = 5).

<p>A comparison of the antimicrobial activity of <i>E</i>. <i>japonica</i> and SNC using the disk diffusion method (<i>n</i> = 5).</p