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1.
The antibacterial activity of photocatalytic titanium dioxide (TiO 2) substrates is induced primarily by UV light irradiation. Recently, nitrogen- and carbon-doped TiO 2 substrates were shown to exhibit photocatalytic activities under visible-light illumination. Their antibacterial activity, however, remains to be quantified. In this study, we demonstrated that nitrogen-doped TiO 2 substrates have superior visible-light-induced bactericidal activity against Escherichia coli compared to pure TiO 2 and carbon-doped TiO 2 substrates. We also found that protein- and light-absorbing contaminants partially reduce the bactericidal activity of nitrogen-doped TiO 2 substrates due to their light-shielding effects. In the pathogen-killing experiment, a significantly higher proportion of all tested pathogens, including Shigella flexneri, Listeria monocytogenes, Vibrio parahaemolyticus, Staphylococcus aureus, Streptococcus pyogenes, and Acinetobacter baumannii, were killed by visible-light-illuminated nitrogen-doped TiO 2 substrates than by pure TiO 2 substrates. These findings suggest that nitrogen-doped TiO 2 has potential application in the development of alternative disinfectants for environmental and medical usages. 相似文献
2.
BackgroundTitania dioxide (TiO 2) photocatalyst is primarily induced by ultraviolet light irradiation. Visible-light responsive anion-doped TiO 2 photocatalysts contain higher quantum efficiency under sunlight and can be used safely in indoor settings without exposing to biohazardous ultraviolet light. The antibacterial efficiency, however, remains to be further improved. Methodology/Principal FindingsUsing thermal reduction method, here we synthesized silver-nanostructures coated TiO 2 thin films that contain a high visible-light responsive antibacterial property. Among our tested titania substrates including TiO 2, carbon-doped TiO 2 [TiO 2 (C)] and nitrogen-doped TiO 2 [TiO 2 (N)], TiO 2 (N) showed the best performance after silver coating. The synergistic antibacterial effect results approximately 5 log reductions of surviving bacteria of Escherichia coli, Streptococcus pyogenes, Staphylococcus aureus and Acinetobacter baumannii. Scanning electron microscope analysis indicated that crystalline silver formed unique wire-like nanostructures on TiO 2 (N) substrates, while formed relatively straight and thicker rod-shaped precipitates on the other two titania materials. Conclusion/SignificanceOur results suggested that proper forms of silver on various titania materials could further influence the bactericidal property. 相似文献
3.
The purpose of the present study was to evaluate the risk of inducing bacterial resistance to disinfection treatment with photolysis of H 2O 2 and comparing this with existing antibacterial agents. We tested seven antibacterial agents, including amoxicillin, cefepime hydrochloride, erythromycin, ofloxacin, clindamycin hydrochloride, ciprofloxacin hydrochloride, and minocycline hydrochloride, as positive controls for validation of the assay protocol. For all of the agents tested, at least one of the four bacterial species ( Staphylococcus aureus, Enterococcus faecalis, Escherichia coli, and Streptococcus salivarius) was resistant to these agents by repeated exposure to subinhibitory concentrations of the agents up to 10 times. In contrast, antibacterial activity against any of the bacterial species tested ( S. aureus, E. faecalis, E. coli, S. salivarius, Pseudomonas aeruginosa, Streptococcus mutans, and Aggregatibacter actinomycetemcomitans) was not affected by repeated exposure to the disinfection treatment up to 40 times. This finding suggested that the risk of inducing bacterial resistance by disinfection treatment was low. The active ingredient of this disinfection treatment is hydroxyl radicals generated by photolysis of H 2O 2. Therefore, hydroxyl radicals interact with several cell structures and different metabolic pathways in microbial cells, probably resulting in a lack of development of bacterial resistance. In conclusion, disinfection treatment with photolysis of H 2O 2 appears to be a potential alternative for existing antimicrobial agents in terms of a low risk of inducing bacterial resistance. 相似文献
4.
BackgroundTraditional antibacterial photocatalysts are primarily induced by ultraviolet light to elicit antibacterial reactive oxygen species. New generation visible-light responsive photocatalysts were discovered, offering greater opportunity to use photocatalysts as disinfectants in our living environment. Recently, we found that visible-light responsive platinum-containing titania (TiO 2–Pt) exerted high performance antibacterial property against soil-borne pathogens even in soil highly contaminated water. However, its physical and photocatalytic properties, and the application in vivo have not been well-characterized. MethodsTransmission electron microscopy, energy dispersive spectroscopy, X-ray photoelectron spectroscopy, X-ray diffraction, ultraviolet–visible absorption spectrum and the removal rate of nitrogen oxides were therefore analyzed. The antibacterial performance under in vitro and in vivo conditions was evaluated. ResultsThe apparent quantum efficiency for visible light illuminated TiO 2–Pt is relatively higher than several other titania photocatalysts. The killing effect achieved approximately 2 log reductions of pathogenic bacteria in vitro. Illumination of injected TiO 2–Pt successfully ameliorated the subcutaneous infection in mice. ConclusionsThis is the first demonstration of in vivo antibacterial use of TiO 2–Pt nanoparticles. When compared to nanoparticles of some other visible-light responsive photocatalysts, TiO 2–Pt nanoparticles induced less adverse effects such as exacerbated platelet clearance and hepatic cytotoxicity in vivo. General significanceThese findings suggest that the TiO 2–Pt may have potential application on the development of an antibacterial material in both in vitro and in vivo settings. 相似文献
5.
Background: Cutaneous leishmaniasis is a parasitic disease, which is difficult to treat due to high drug resistance and adverse side effects. Photodynamic therapy by ultraviolet radiation using materials with high photocatalytic features like titanium dioxide nanoparticles (TiO 2-NPs) is an emerging treatment for this disease. In this study, TiO 2-NPs with ultraviolet (UV) radiation were administered as photodynamic therapy against Leishmania Major (LM) promastigotes.Methods: Two forms of TiO 2 viz. including Anatase and Rutile were administered in two UV ranges< UVA and UVB for different time periods (30 and 60 min). Finally, 24 and 48 h after incubation, the MTS test was performed and cell survival percentage was calculated.Results: The mean size of Anatase and Rutile-NPs is approximately 32.5 and 50.9 nm respectively by DLS and FE-SEM, and crystal phase is emphasized by XRD. The combined treatment of LM with TiO 2-NPs and UV has significant effects on LM promastigotes, which vary depending on NP and UV types. The synergistic effect was anticipated in the groups irradiated by UV-B in the presence of Rutile NPs.Conclusion: The combined treatment with UV- radiation and TiO 2-NPs can be effective in killing the promastigotes of Leishmania major. The proper concentration of NPs and the type of UV-radiation must be taken into consideration. The results suggest improved treatment methods, after proper in vivo studies. 相似文献
6.
Listeria monocytogenes is the agent of listeriosis, a food-borne disease. It represents a serious problem for the food industry because of its environmental persistence mainly due to its ability to form biofilm on a variety of surfaces. Microrganisms attached on the surfaces are a potential source of contamination for environment and animals and humans. Titanium dioxide nanoparticles (TiO 2 NPs) are used in food industry in a variety of products and it was reported that daily exposure to these nanomaterials is very high. Anti-listerial activity of TiO 2 NPs was investigated only with UV-irradiated nanomaterials, based on generation of reactive oxigen species (ROS) with antibacterial effect after UV exposure. Since both Listeria monocytogenes and TiO 2 NPs are veicolated with foods, this study explores the interaction between Listeria monocytogenes and non UV-irradiated TiO 2 NPs, with special focus on biofilm formation and intestinal cell interaction. Scanning electron microscopy and quantitative measurements of biofilm mass indicate that NPs influence both production and structural architecture of listerial biofilm. Moreover, TiO 2 NPs show to interfere with bacterial interaction to intestinal cells. Increased biofilm production due to TiO 2 NPs exposure may favour bacterial survival in environment and its transmission to animal and human hosts. 相似文献
7.
Bactericidal activity of traditional titanium dioxide (TiO 2) photocatalyst is effective only upon irradiation by ultraviolet light, which restricts the potential applications of TiO 2 for use in our living environments. Recently carbon-containing TiO 2 was found to be photoactive at visible-light illumination that affords the potential to overcome this problem; although, the bactericidal activity of these photocatalysts is relatively lower than conventional disinfectants. Evidenced from scanning electron microscopy and confocal Raman spectral mapping analysis, we found the interaction with bacteria was significantly enhanced in these anatase/rutile mixed-phase carbon-containing TiO 2. Bacteria-killing experiments indicate that a significantly higher proportion of all tested pathogens including Staphylococcus aureus, Shigella flexneri and Acinetobacter baumannii, were eliminated by the new nanoparticle with higher bacterial interaction property. These findings suggest the created materials with high bacterial interaction ability might be a useful strategy to improve the antimicrobial activity of visible-light-activated TiO 2. 相似文献
8.
This work focuses on the photocatalytic performances and antibacterial activity of nitrogen doped TiO 2 nanosystems with three and five layers obtained by a sol-gel route, followed by thermal treatment in oxygen or ammonia atmosphere
at temperatures between 400 and 1000°C. Subsequently, the antibacterial activity of the obtained nanosystems on the Escherichia coli cells are determined and discussed. The obtained results show a significant dependence of the functional performances on
the system’s composition. In particular, the antimicrobial activity of nitrogen-doped TiO 2 films is correlated with the temperature of thermal treatment and illumination time with visible artificial light. 相似文献
9.
Photocatalytically active nanostructures require a large specific surface area with the presence of many catalytically active sites for the oxidation and reduction half reactions, and fast electron (hole) diffusion and charge separation. Nanowires present suitable architectures to meet these requirements. Axially segmented Ag|ZnO and radially segmented (coaxial) TiO 2-Ag nanowires with a diameter of 200 nm and a length of 6-20 µm were made by templated electrodeposition within the pores of polycarbonate track-etched (PCTE) or anodized aluminum oxide (AAO) membranes, respectively. In the photocatalytic experiments, the ZnO and TiO 2 phases acted as photoanodes, and Ag as cathode. No external circuit is needed to connect both electrodes, which is a key advantage over conventional photo-electrochemical cells. For making segmented Ag|ZnO nanowires, the Ag salt electrolyte was replaced after formation of the Ag segment to form a ZnO segment attached to the Ag segment. For making coaxial TiO 2-Ag nanowires, a TiO 2 gel was first formed by the electrochemically induced sol-gel method. Drying and thermal annealing of the as-formed TiO 2 gel resulted in the formation of crystalline TiO 2 nanotubes. A subsequent Ag electrodeposition step inside the TiO 2 nanotubes resulted in formation of coaxial TiO 2-Ag nanowires. Due to the combination of an n-type semiconductor (ZnO or TiO 2) and a metal (Ag) within the same nanowire, a Schottky barrier was created at the interface between the phases. To demonstrate the photocatalytic activity of these nanowires, the Ag|ZnO nanowires were used in a photocatalytic experiment in which H 2 gas was detected upon UV illumination of the nanowires dispersed in a methanol/water mixture. After 17 min of illumination, approximately 0.2 vol% H 2 gas was detected from a suspension of ~0.1 g of Ag|ZnO nanowires in a 50 ml 80 vol% aqueous methanol solution. 相似文献
10.
Photochemical treatment is increasingly being applied to remedy environmental problems. TiO 2-derived catalysts are efficiently and widely used in photodegradation applications. The efficiency of various photochemical treatments, namely, the use of UV irradiation without catalyst or with TiO 2/graphene-TiO 2 photodegradation methods was determined by comparing the photodegadation of two main types of hydrophobic chlorinated aromatic pollutants, namely, pentachlorophenol (PCP) and polychlorinated biphenyls (PCBs). Results show that photodegradation in methanol solution under pure UV irradiation was more efficient than that with either one of the catalysts tested, contrary to previous results in which photodegradation rates were enhanced using TiO 2-derived catalysts. The effects of various factors, such as UV light illumination, addition of methanol to the solution, catalyst dosage, and the pH of the reaction mixture, were examined. The degradation pathway was deduced. The photochemical treatment in methanol soil washing solution did not benefit from the use of the catalysts tested. Pure UV irradiation was sufficient for the dechlorination and degradation of the PCP and PCBs. 相似文献
11.
Organic contaminants adsorbed on the surface of titanium dioxide (TiO 2) can be decomposed by photocatalysis under ultraviolet (UV) light. Here we describe a novel protocol employing the TiO 2 photocatalysis to locally alter cell affinity of the substrate surface. For this experiment, a thin TiO 2 film was sputter-coated on a glass coverslip, and the TiO 2 surface was subsequently modified with an organosilane monolayer derived from octadecyltrichlorosilane (OTS), which inhibits cell adhesion. The sample was immersed in a cell culture medium, and focused UV light was irradiated to an octagonal region. When a neuronal cell line PC12 cells were plated on the sample, cells adhered only on the UV-irradiated area. We further show that this surface modification can also be performed in situ, i.e., even when cells are growing on the substrate. Proper modification of the surface required an extracellular matrix protein collagen to be present in the medium at the time of UV irradiation. The technique presented here can potentially be employed in patterning multiple cell types for constructing coculture systems or to arbitrarily manipulate cells under culture. 相似文献
12.
The pollution of raw surface and underground water with pharmaceutical compounds has an impact on increasing the resistance of pathogenic microorganisms. Environmental challenges include investigating a novel and cost-effective therapeutic approach for the bactericidal treatment of water supplies. Ethyl acetate extracts from three marine algae (Caulerpa racemosa, Codium fragile, and Cystoseira myrica) obtained from the Red Sea (Hurghada, Egypt) were used for the green synthesis of TiO2 nanoparticles (TiO2-NPs). A highly crystalline nanoparticle structure with a stable tetragonal anatase structure was obtained; the mean concentrations were 2.43 to 6.09?×?108 NPs/mL and the average particle size was 125–131 nm. In ultrapure water, the TiO2-NPs were confirmed to be a stable solution following zeta potential analysis. UV light (λ?=?350 nm) for 2 h was used to activate the TiO2-NPs before the antibacterial activity tests. The application of UV-activated TiO2-NPs for 4 h treatments demonstrated promising bactericidal activity, with a 73.08% reduction in Salmonella typhi and a 91.51% reduction in Enterobacter ludwigii. Antibiofilm activities against the reference strains Salmonella typhi NCTC 12023/ATTC and Morganella morganii ATCC25829 and the bacterial isolates Klebsiella pneumoniae, Enterobacter ludwigii, and Enterococcus faecium were tested. The TiO2-NPs were nontoxic against the human normal cell line RPE1. Regarding the treatment of total and fecal coliform, in addition to fecal streptococci, in raw surface and underground water, the UV-activated TiO2-NPs prepared from the ethyl acetate extracts of Caulerpa racemosa showed high applicability. The present study offered insights into the nature and development of nontoxic and green TiO2-NP formulations for use as modern antibacterial alternatives against coliforms in aquatic systems. 相似文献
13.
Controversial and inconsistent results on the eco-toxicity of TiO 2 nanoparticles (NPs) are commonly found in recorded studies and more experimental works are therefore warranted to elucidate the nanotoxicity and its underlying precise mechanisms. Toxicities of five types of TiO 2 NPs with different particle sizes (10∼50 nm) and crystal phases were investigated using Escherichia coli as a test organism. The effect of water chemistry on the nanotoxicity was also examined. The antibacterial effects of TiO 2 NPs as revealed by dose-effect experiments decreased with increasing particle size and rutile content of the TiO 2 NPs. More bacteria could survive at higher solution pH (5.0–10.0) and ionic strength (50–200 mg L −1 NaCl) as affected by the anatase TiO 2 NPs. The TiO 2 NPs with anatase crystal structure and smaller particle size produced higher content of intracellular reactive oxygen species and malondialdehyde, in line with their greater antibacterial effect. Transmission electron microscopic observations showed the concentration buildup of the anatase TiO 2 NPs especially those with smaller particle sizes on the cell surfaces, leading to membrane damage and internalization. These research results will shed new light on the understanding of ecological effects of TiO 2 NPs. 相似文献
14.
Interfacial studies and band alignment engineering on the electron transport layer (ETL) play a key role for fabrication of high‐performance perovskite solar cells (PSCs). Here, an amorphous layer of SnO 2 (a‐SnO 2) between the TiO 2 ETL and the perovskite absorber is inserted and the charge transport properties of the device are studied. The double‐layer structure of TiO 2 compact layer (c‐TiO 2) and a‐SnO 2 ETL leads to modification of interface energetics, resulting in improved charge collection and decreased carrier recombination in PSCs. The optimized device based on a‐SnO 2/c‐TiO 2 ETL shows a maximum power conversion efficiency (PCE) of 21.4% as compared to 19.33% for c‐TiO 2 based device. Moreover, the modified device demonstrates a maximum open‐circuit voltage ( Voc) of 1.223 V with 387 mV loss in potential, which is among the highest reported value for PSCs with negligible hysteresis. The stability results show that the device on c‐TiO 2/a‐SnO 2 retains about 91% of its initial PCE value after 500 h light illumination, which is higher than pure c‐TiO 2 (67%) based devices. Interestingly, using a‐SnO 2/c‐TiO 2 ETL the PCE loss was only 10% of initial value under continuous UV light illumination after 30 h, which is higher than that of c‐TiO 2 based device (28% PCE loss). 相似文献
15.
Current exanimation reports, green fabrication of silver doped TiO 2 nanoparticles (Ag/TiO 2) using aqueous extract of Acacia nilotica as bio-reductant and assess its potential as antimicrobial and anticancer agent. The obtained spherical Ag/TiO 2 were characterized by various analytical techniques including FTIR, (XRD), (FE-SEM EDS), and (TEM). Synthesized Ag/TiO 2 demonstrated broad spectrum antibacterial and anticandidal activity. The order of antimicrobial activity was found to be E. coli > C. albicans > MRSA > P. aeruginosa. In addition, cytotoxicity and oxidative stress of Ag/TiO 2 nanoparticles in (MCF-7) cells was also investigated. Outcomes of MTT assay showed concentration dependent reduction in cell viability. Further, synthesized NPs reduced the level of glutathione, induced ROS generation and lipid peroxidation in the treated cells. Therefore, it is envisaged that these spherical nanoparticles may be exploited in drug delivery, pharmaceutical, and food industry. 相似文献
16.
In this study, Ag is electron-beam evaporated to modify the topography of anodic TiO 2 nanotubes of different diameters to obtain an implant with enhanced antibacterial activity and biocompatibility. We found that highly hydrophilic as-grown TiO 2 nanotubes became poorly hydrophilic with Ag incorporation; however they could effectively recover their wettability to some extent under ultraviolet light irradiation. The results obtained from antibacterial tests suggested that the Ag-decorated TiO 2 nanotubes could greatly inhibit the growth of Staphylococcus aureus. In vitro biocompatibility evaluation indicated that fibroblast cells exhibited an obvious diameter-dependent behavior on both as-grown and Ag-decorated TiO 2 nanotubes. Most importantly, of all samples, the smallest diameter (25-nm-diameter) Ag-decorated nanotubes exhibited the most obvious biological activity in promoting adhesion and proliferation of human fibroblasts, and this activity could be attributed to the highly irregular topography on a nanometric scale of the Ag-decorated nanotube surface. These experimental results demonstrate that by properly controlling the structural parameters of Ag-decorated TiO 2 nanotubes, an implant surface can be produced that enhances biocompatibility and simultaneously boosts antibacterial activity. 相似文献
17.
Fouling-release (FR) coatings minimise the adhesion strength of fouling organisms. This study describes improved technologies to control the settlement and adhesion of the important fouling organism Mytilus galloprovincialis by incorporating the nanofillers titanium dioxide (TiO 2) and carbon nanotubes (CNTs) in polydimethylsiloxane (PDMS) matrices. The incorporation of TiO 2 prevented larval settlement when photoactivated with UV light, even at the lowest concentration of the nanofiller (3.75 wt%). Notably, there was 100% mortality of pediveligers exposed to photoactivated TiO 2. However, plantigrades initially settled to photoactivated TiO 2, but their adhesion strength was significantly reduced on these surfaces in comparison to blank PDMS. In addition, plantigrades had high mortality after 6 h. In contrast to the enhanced antifouling and FR properties of PDMS incorporating TiO 2, the incorporation of CNTs had no effect on the settlement and adhesion of M. galloprovincialis. 相似文献
18.
When titanium dioxide (TiO 2) is irradiated with near-UV light, this semiconductor exhibits strong bactericidal activity. In this paper, we present the first evidence that the lipid peroxidation reaction is the underlying mechanism of death of Escherichia coli K-12 cells that are irradiated in the presence of the TiO 2 photocatalyst. Using production of malondialdehyde (MDA) as an index to assess cell membrane damage by lipid peroxidation, we observed that there was an exponential increase in the production of MDA, whose concentration reached 1.1 to 2.4 nmol · mg (dry weight) of cells −1 after 30 min of illumination, and that the kinetics of this process paralleled cell death. Under these conditions, concomitant losses of 77 to 93% of the cell respiratory activity were also detected, as measured by both oxygen uptake and reduction of 2,3,5-triphenyltetrazolium chloride from succinate as the electron donor. The occurrence of lipid peroxidation and the simultaneous losses of both membrane-dependent respiratory activity and cell viability depended strictly on the presence of both light and TiO 2. We concluded that TiO 2 photocatalysis promoted peroxidation of the polyunsaturated phospholipid component of the lipid membrane initially and induced major disorder in the E. coli cell membrane. Subsequently, essential functions that rely on intact cell membrane architecture, such as respiratory activity, were lost, and cell death was inevitable. 相似文献
19.
Employing the antibacterial property of industrial bamboo vinegar (IBV) and the photocatalytic degradation of TiO 2, bamboo macromolecules were pretreated and processed into nonvolatile and antibacterial bio board (NVABB). The NVABB was then analyzed by conducting Fourier-transform infrared spectroscopy, thermogravimetric analysis and differential thermal analysis. Results show that NVABB samples had average density of 0.96?g/cm 3, which is appropriate for application. In terms of physical and mechanical properties, the best NVABB sample obtained from IBV, TiO 2 and bamboo had an IBV pretreatment time of 10?min, 2% TiO 2 and 1% bamboo charcoal. Fourier-transform infrared spectroscopy demonstrated that optimum conditions for hot pressing were a temperature of 170?°C, duration of 15?min and the addition of IBV and TiO 2. Thermogravimetric analysis/differential thermal analysis curves suggest that the thermal degradation of NVABB was less than that of bamboo and that hot pressing obviously increased the thermal stability of HDBB samples. Analysis of the antimicrobial effect revealed that IBV pretreatment improves the antibacterial property of NVABB. 相似文献
20.
The potential toxicity of nanoparticles in plants is scarce and contradictory. Despite the diversity of research efforts, a detailed explanation of the TiO 2NPS effects in plant photosynthesis is still missing. The present work gives a new approach to examine the impact of the TiO 2NPs on crop production (development and photosynthesis) and plant protection (tolerance and defense systems) in fenugreek ( Trigonella foenum graecum L.). Seedlings were assessed in greenhouse trials to estimate the influence of TiO 2NPs on physiological characters for 16 days. They were treated with TiO 2NPs at a size less than 20 nm. The results revealed that there were no significant effects on seedlings growth and biomass of stem, but a decrease in the fresh weight of leaves after TiO 2NPs treatment. Plants treated with 100 mg·L ?1 of TiO 2NPs presented a reduction and chlorosis in leaf area due to a significant decrease in the chlorophyll a and b contents. The highest value of the photosynthetic pigments was recorded at 50 mg·L ?1 of TiO 2NPs. However, the treatment with 100 mg·L ?1 of TiO 2NPs caused a decrease in the levels of chlorophyll a, b and of carotenoids. Both doses of TiO 2NPs induced an accumulation of anthocyanins compared to the control after 16 days of seedling development. A nano-stress significantly decreased the flavonoids level, but increased that of polyphenols compared to control after 16 days of exposure. The decrease in the translocation ratio of flavonoids suggests that many of them contain an enediol group, which suggests that they may act as bidentate ligands for anatase TiO 2NPs. Accordingly, nano-stressed leaves exhibited significantly enhanced GPOX, CAT and APX activity levels. On the contrary, GPOX and CAT activities were reduced substantially in stems treated with 100 mg·L ?1 TiO 2NPs. The accumulation of MDA was found to be higher in stems than in leaves. This could be explained by the accumulation of nanoparticles in different organs; it could be that the stems are the favored targets of nanoparticles. These results underline the necessity for a deeper estimation of nanoparticle ecotoxicity and particularly concerning their interaction with plants. 相似文献
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