Effects of coating materials on antibacterial properties of industrial and sunscreen-derived titanium-dioxide nanoparticles on Escherichia coli

Aging effects of titanium dioxide on Cu toxicity to Daphnia magna: Exploring molecular docking and significance of surface properties

Cosmetics and personal care products containing titanium dioxide nanoparticles (TiO2 NPs) may enter aquatic environments, where the surface coatings of TiO2 NPs may change with aging due to environmental factors such as light, and potentially affect their bioaccumulation and toxicity. This study examined how aging impacted the physicochemical properties of three commercially available TiO2 NPs and subsequent influence on the bioaccumulation and toxicity of copper (Cu) in Daphnia magna (D. magna). We demonstrated that aging significantly affected the hydrophobicity of TiO2 NPs, which affected their binding to water molecules and adsorption of Cu. Changes of bioaccumulation of TiO2 NPs and Cu in D. magna ultimately affected the activities of intracellular antioxidant enzymes such as SOD, CAT, GSH-Px, and the transmembrane protein Na+/K+-ATPase. Molecular docking calculations demonstrated that changes of activities of these biological enzymes were due to the interaction between TiO2 NPs, Cu, and amino acid residues near the sites with the lowest binding energy and active center of the enzyme. Such effect was closely related to the hydrophobicity of TiO2 NPs. Our study demonstrated the close relationship between surface properties of TiO2 NPs and their biological effects, providing important evidence for understanding the behavior of nanomaterials in aquatic environments.

Creating anti-viral high-touch surfaces using photocatalytic transparent films

Antimicrobial and self-cleaning surface coatings are promising tools to combat the growing global threat of infectious diseases and related healthcare-associated infections (HAIs). Although many engineered TiO₂-based coating technologies are reporting antibacterial performance, the antiviral performance of these coatings has not been explored. Furthermore, previous studies have underscored the importance of the "transparency" of the coating for surfaces such as the touch screens of medical devices. Hence, in this study, we fabricated a variety of nanoscale TiO₂-based transparent thin films (anatase TiO₂, anatase/rutile mixed phase TiO₂, silver-anatase TiO₂ composite, and carbon nanotube-anatase TiO₂ composite) via dipping and airbrush spray coating technologies and evaluated their antiviral performance (Bacteriophage MS2 as the model) under dark and illuminated conditions. The thin films showed high surface coverage (ranging from 40 to 85%), low surface roughness (maximum average roughness 70 nm), super-hydrophilicity (water contact angle 6-38.4°), and high transparency (70-80% transmittance under visible light). Antiviral performance of the coatings revealed that silver-anatase TiO₂ composite (nAg/nTiO₂) coated samples achieved the highest antiviral efficacy (5-6 log reduction) while the other TiO₂ coated samples showed fair antiviral results (1.5-3.5 log reduction) after 90 min LED irradiation at 365 nm. Those findings indicate that TiO₂-based composite coatings are effective in creating antiviral high-touch surfaces with the potential to control infectious diseases and HAIs.

Khalaf AA, R. Zaki A, Mansour Khalifa M, A. Ibrahim M, M. Mekkawy A, E. Abdelrahman R, Farghali A, A. Noshy P. Hesperidin protects rats’ liver and kidney from oxidative damage and physiological disruption induced by nickel oxide nanoparticles

Background: Nickel oxide nanoparticles (NiO-NPs) have recently been utilized in various advanced industrial fields like lithium-ion micro batteries, nanofibers, electrochromic devices, and several biomedical applications. NiO-NPs are classified as extremely toxic substances as they can cause long-term harm to the environment and aquatic life. Moreover, frequent and prolonged exposure can affect human and animal health, causing skin allergies and major toxic consequences, such as hepatorenal toxicity. Hesperidin (HSP) has been proven to possess anti-inflammatory, antioxidant, and free radical scavenging activities.

Objective: This study aimed to investigate the underlying protective mechanisms and effects of HSP against NiO-NPs-induced hepatorenal toxicities in rats.

Materials and Methods: Forty male Wistar rats were randomly divided into four groups (n = 10 in each). The first group served as a Control group. For 8 weeks, the second group was administered NiO-NPs (100 mg/kg/day), and the third group was given HSP (100 mg/kg/day) via oral gavage for both groups. The fourth group received NiO-NPs and HSP concurrently in the same oral daily doses and duration as the second and third groups.

Results: NiO-NPs administration revealed a significant increase in plasma biomarkers of nephrotoxicity (urea, creatinine) and hepatotoxicity (ALT, AST) in NiO-NPs group compared to Control group (p < 0.05). In addition, NiO-NPs administration resulted in a substantial increase in malondialdehyde levels with a significant drop in catalase activity and GSH content in Group II. Also, a significant decreased expression of Nrf-2 and Bcl-2 mRNA levels and upregulation of TNF-α, NF-kβ and BAX in the liver and kidney of NiO-NPs group were also detected. Histologically, the liver and kidney of rats of NiO-NPs group showed significant histopathological disturbances, with a substantial increase in the proliferating cell nuclear antigen (PCNA) positive hepatocytes and renal tubular cells in the NiO-NPs group compared to Control and HSP groups (p < 0.05). In contrast, concomitant administration of HSP with NiO-NPs in group IV showed a significant biochemical, histopathological, and immunohistochemical improvement compared to NiO-NPs group.

Conclusion: Co-administration of HSP with NiO-NPs significantly ameliorated most of the NiO-NPs-induced hepatorenal toxicities in male rats.

Evaluation of TiO2 Nanoparticles Physicochemical Parameters Associated with their Antimicrobial Applications

Titanium dioxide nanoparticles (TiO2NPs) usage is increasing in everyday consumer products, hence, assessing their toxic impacts on living organisms and environment is essential. Various studies have revealed the significant role of TiO2NPs physicochemical properties on their toxicity. However, TiO2NPs are still poorly characterized with respect to their physicochemical properties, and environmental factors influencing their toxicity are either ignored or are too complex to be assessed under laboratory conditions. The outcomes of these studies are diverse and inconsistent due to lack of standard protocols. TiO2NPs toxicity also differs for in vivo and in vitro systems, which must also be considered during standardization of protocols to maintain uniformity and reproducibility of results. This review critically evaluates impact of different physicochemical parameters of TiO2NPs and other experimental conditions, employed in different laboratories in determining their toxicity towards bacteria. These important observations may be helpful in evaluation of environmental risks posed by these nanoparticles and this can further assist regulatory bodies in policymaking.

Toxicity assessment of TiO2-conjugated Carbon-based nanohybrid material on a freshwater bioindicator cladoceran, Daphnia magna

The application of nanocomposite materials fabricated from titanium dioxide nanoparticles (TiO₂ NPs) and different carbon (C) allotropes have gained popularity in water treatment applications due to their synergistic properties. Studies to date have focused on simple forms of nanomaterials (NMs), however, with the technology development, there is a dramatic increase in production and application of these complex NMs which could result in toxicological impacts on organisms when released into aquatic environments. This raises serious concerns about their safety and the need to ascertain their potential adverse effects on aquatic organisms. While conjugated TiO₂ NPs/carbon-based nanohybrids (TiO₂/C-NHs) may exhibit enhanced photocatalytic activity, there is no research in the scientific community regarding their toxicological effects on D. magna, which are indicators of freshwater pollution. In this study, two under-represented TiO₂/C-NHs (i.e., TiO₂- conjugated carbon nanofiber (CNF), and TiO₂-conjugated multi-walled carbon nanotube (CNT)) were investigated for their toxic effects on D. magna, through a series of acute toxicity tests with a set of sublethal biochemical biomarkers of oxidative stress. The lethal toxicity and oxidative stress formation of TiO₂/C-NHs over 48 h revealed a concentration-dependant increase in D. magna mortality. The primary mechanism identified was the generation of ROS, which was in line with toxicity results. Light microscopy and CytoViva® images visualized D. magna interaction with the NPs, which accumulated and appeared as dark materials in the lines of the gut tract. The collective results indicate that TiO₂/C-NHs have the potential to cause an effect on freshwater organisms when released into the environment. However, the relevance of TiO₂/C-NHs effects needs further chronic toxicity studies since they show promise to be used in nano-bioremediation materials to treat wastewaters.

Safe-and-Sustainable-by-Design Framework Based on a Prospective Life Cycle Assessment: Lessons Learned from a Nano-Titanium Dioxide Case Study

Safe-and-sustainable-by-design (SSbD) is a concept that takes a systems approach by integrating safety, sustainability, and functionality throughout a product’s the life cycle. This paper proposes a framework based on a prospective life cycle assessment for early safety and sustainability assessment. The framework’s purpose is to identify environmental sustainability and toxicity hotspots early in the innovation process for future SSbD applicability. If this is impossible, key performance indicators are assessed. Environmental sustainability aspects, such as global warming potential (GWP) and cumulative energy demand (CED), and toxicity aspects, such as human toxicity potential and freshwater ecotoxicity potential, were assessed upon applying the framework on a case study. The case study regarded using nano-titanium dioxide (P25-TiO₂) or a modified nano-coated version (Cu₂O-coated/P25-TiO₂) as photocatalysts to produce hydrogen from water using sunlight. Although there was a decrease in environmental impact (GWP and CED), the modified nano-coated version had a relatively higher level of human toxicity and freshwater eco-toxicity. For the presented case study, SSbD alternatives need to be considered that improve the photocatalytic activity but are not toxic to the environment. This case study illustrates the importance of performing an early safety and environmental sustainability assessment to avoid the development of toxic alternatives.

Environmental Fate and Toxicity of Sunscreen-Derived Inorganic Ultraviolet Filters in Aquatic Environments: A Review

An increasing number of inorganic ultraviolet filters (UVFs), such as nanosized zinc oxide (nZnO) and titanium dioxide (nTiO2), are formulated in sunscreens because of their broad UV spectrum sunlight protection and because they limit skin damage. However, sunscreen-derived inorganic UVFs are considered to be emerging contaminants; in particular, nZnO and nTiO2 UVFs have been shown to undergo absorption and bioaccumulation, release metal ions, and generate reactive oxygen species, which cause negative effects on aquatic organisms. We comprehensively reviewed the current study status of the environmental sources, occurrences, behaviors, and impacts of sunscreen-derived inorganic UVFs in aquatic environments. We find that the associated primary nanoparticle characteristics and coating materials significantly affect the environmental behavior and fate of inorganic UVFs. The consequential ecotoxicological risks and underlying mechanisms are discussed at the individual and trophic transfer levels. Due to their persistence and bioaccumulation, more attention and efforts should be redirected to investigating the sources, fate, and trophic transfer of inorganic UVFs in ecosystems.

Aquatic Environment Exposure and Toxicity of Engineered Nanomaterials Released from Nano-Enabled Products: Current Status and Data Needs

Rapid commercialisation of nano-enabled products (NEPs) elevates the potential environmental release of engineered nanomaterials (ENMs) along the product life cycle. The current review examined the state of the art literature on aquatic environment exposure and ecotoxicity of product released (PR) engineered nanomaterials (PR-ENMs). Additionally, the data obtained were applied to estimate the risk posed by PR-ENMs to various trophic levels of aquatic biota as a means of identifying priority NEPs cases that may require attention with regards to examining environmental implications. Overall, the PR-ENMs are predominantly associated with the matrix of the respective NEPs, a factor that often hinders proper isolation of nano-driven toxicity effects. Nevertheless, some studies have attributed the toxicity basis of observed adverse effects to a combination of the released ions, ENMs and other components of NEPs. Notwithstanding the limitation of current ecotoxicology data limitations, the risk estimated herein points to an elevated risk towards fish arising from fabrics' PR-nAg, and the considerable potential effects from sunscreens' PR-nZnO and PR-nTiO2 to algae, echinoderms, and crustaceans (PR-nZnO), whereas PR-nTiO2 poses no significant risk to echinoderms. Considering that the current data limitations will not be overcome immediately, we recommend the careful application of similar risk estimation to isolate/prioritise cases of NEPs for detailed characterisation of ENMs' release and effects in aquatic environments.

Assessment of Nanopollution from Commercial Products in Water Environments

The use of nano-enabled products (NEPs) can release engineered nanomaterials (ENMs) into water resources, and the increasing commercialisation of NEPs raises the environmental exposure potential. The current study investigated the release of ENMs and their characteristics from six commercial products (sunscreens, body creams, sanitiser, and socks) containing nTiO2, nAg, and nZnO. ENMs were released in aqueous media from all investigated NEPs and were associated with ions (Ag+ and Zn2+) and coating agents (Si and Al). NEPs generally released elongated (7-9 × 66-70 nm) and angular (21-80 × 25-79 nm) nTiO2, near-spherical (12-49 nm) and angular nAg (21-76 × 29-77 nm), and angular nZnO (32-36 × 32-40 nm). NEPs released varying ENMs' total concentrations (ca 0.4-95%) of total Ti, Ag, Ag+, Zn, and Zn2+ relative to the initial amount of ENMs added in NEPs, influenced by the nature of the product and recipient water quality. The findings confirmed the use of the examined NEPs as sources of nanopollution in water resources, and the physicochemical properties of the nanopollutants were determined. Exposure assessment data from real-life sources are highly valuable for enriching the robust environmental risk assessment of nanotechnology.

Sunscreens’ UV Filters Risk for Coastal Marine Environment Biodiversity: A Review

Considering the rapid growth of tourism in recent years and the acknowledgement that exposure to solar UV radiation may cause skin cancer, sunscreens have been widely used by beachgoers in recent decades. UV filters contained in sunscreens, however, were recently identified as emerging pollutants in coastal waters since they accumulate in the marine environment with different adverse effects. In fact, exposure to these components was proven to be toxic to most invertebrate and vertebrate marine species. Some UV filters are linked to the production of significant amounts of reactive oxygen species (ROS), such as hydrogen peroxide, and the release of inorganic micronutrients that may alter the status of coastal habitats. Bioaccumulation and biomagnification have not yet been fully addressed. This review highlights recent progress in research and provides a comprehensive overview of the toxicological and ecotoxicological effects of the most used UV filters both on the abiotic and biotic compartments in different types of coastal areas, to gain a better understanding of the impacts on coastal biodiversity.

Bioinspired Green Synthesis of Chitosan and Zinc Oxide Nanoparticles with Strong Antibacterial Activity against Rice Pathogen Xanthomonas oryzae pv. oryzae

Bacterial leaf blight caused by Xanthomonas oryzae pv. oryzae (Xoo) is one of the most devastating diseases, resulting in significant yield losses in rice. The extensive use of chemical antibacterial agents has led to an increase the environmental toxicity. Nanotechnology products are being developed as a promising alternative to control plant disease with low environmental impact. In the present study, we investigated the antibacterial activity of biosynthesized chitosan nanoparticles (CSNPs) and zinc oxide nanoparticles (ZnONPs) against rice pathogen Xoo. The formation of CSNPs and ZnONPs in the reaction mixture was confirmed by using UV-vis spectroscopy at 300-550 nm. Moreover, CSNPs and ZnONPs with strong antibacterial activity against Xoo were further characterized by scanning and transmission electron microscopy, Fourier-transform infrared spectroscopy, and X-ray diffraction. Compared with the corresponding chitosan and ZnO alone, CSNPs and ZnONPs showed greater inhibition in the growth of Xoo, which may be mainly attributed to the reduction in biofilm formation and swimming, cell membrane damage, reactive oxygen species production, and apoptosis of bacterial cells. Overall, this study revealed that the two biosynthesized nanoparticles, particularly CSNPs, are a promising alternative to control rice bacterial disease.

Toxicity of ZnO/TiO2 -conjugated carbon-based nanohybrids on the coastal marine alga Thalassiosira pseudonana

Increasing consumption of metal-oxide nanoparticles (NPs) and carbon-based nanomaterials has caused significant concern about their potential hazards in aquatic environments. The release of NPs into aquatic environments could result in adsorption of NPs on microorganisms. While metal-oxide NP-conjugated carbon-based nanohybrids (NHs) may exhibit enhanced toxicity toward microorganisms due to their large surface area and the generation of reactive oxygen species (ROS), there is a lack of information regarding the ecotoxicological effects of NHs on marine diatom algae, which are an indicator of marine pollution. Moreover, there is scant information on toxicity mechanisms of NHs on aquatic organisms. In this study, four NHs (ie, ZnO-conjugated graphene oxide [GO], ZnO-conjugated carbon nanotubes [CNTs], TiO₂ -conjugated GO, and TiO₂ -conjugated CNT) that were synthesized by a hydrothermal method were investigated for their toxicity effects on a Thalassiosira pseudonana marine diatom. The in vitro cellular viability and ROS formation employed at the concentration ranges of 50 and 100 mg/L of NHs over 72 hours revealed that ZnO-GO had the most negative effect on T. pseudonana. The primary mechanism identified was the generation of ROS and GO-induced dispersion that caused electrostatic repulsion, preventing aggregation, and an increase in surface areas of NHs. In contrast to GO-induced dispersion, large aggregates were observed in ZnO/TiO₂ -conjugated CNT-based NHs. The scanning electron microscopy images suggest that NHs covered algae cells and interacted with them (shading effects); this reduced light availability for photosynthesis. Detailed in vitro toxicity effects and mechanisms that cause high adverse acute toxicity on T. pseudonana were unveiled; this implied concerns about potential hazards of these mechanisms in aquatic ecosystems.

Antibacterial effects of graphene- and carbon-nanotube-based nanohybrids on Escherichia coli: Implications for treating multidrug-resistant bacteria

Some nanomaterials including Fe⁰, Ag⁰, and ZnO are well known for their antibacterial effects. However, very few studies have examined antibacterial effects of nanohybrids. Given that metal oxides, mainly ZnO and TiO₂, are known to increase mobility, surface area, and photocatalysis when combined with carbon-based nanomaterials, ZnO- and TiO₂-conjugated carbon nanotube and graphene oxide nanohybrids were investigated for their antibacterial effects on Escherichia coli (DH5α, a multidrug-resistant coliform bacterium). Graphene-oxide (GO)-based nanohybrids (ZnO-GO and TiO₂-GO) induced increased dispersion compared to carbon-nanotube (CNT)-based nanohybrids (ZnO-CNT and TiO₂-CNT). Among the four types of nanohybrids, ZnO-conjugated nanohybrids exhibited a higher antibacterial property, resulting in the antibacterial effect (measured with growth inhibition of cells) in the order ZnO-GO > ZnO-CNT > TiO₂-GO > TiO₂-CNT. Among four possible antibacterial mechanisms (generation of reactive oxygen species (ROS), physicochemical characteristics, the steric effect, and release of metal ions), a primary mechanism-ROS generation-was identified; whereas, physicochemical characteristics and the steric effect were part of contributing mechanisms. The increasing dispersion of TiO₂/ZnO on GO may have contributed to the antibacterial effects due to increasing surface areas. Similarly, significant damages to E. coli cell membranes were found by the GO sheet with its sharp edges. Our results suggest that applying GO-based ZnO or TiO₂ could be an effective antibacterial method, especially for the treatment of multidrug-resistant bacteria in the water.

Characterization and mechanism of the effects of Mg-Fe layered double hydroxide nanoparticles on a marine bacterium: new insights from genomic and transcriptional analyses

BACKGROUND

Layered double hydroxides (LDHs) have received widespread attention for their potential applications in catalysis, polymer nanocomposites, pharmaceuticals, and sensors. Here, the mechanism underlying the physiological effects of Mg-Fe layered double hydroxide nanoparticles on the marine bacterial species Arthrobacter oxidans KQ11 was investigated.

RESULTS

Increased yields of marine dextranase (Aodex) were obtained by exposing A. oxidans KQ11 to Mg-Fe layered double hydroxide nanoparticles (Mg-Fe-LDH NPs). Furthermore, the potential effects of Mg-Fe-LDH NPs on bacterial growth and Aodex production were preliminarily investigated. A. oxidans KQ11 growth was not affected by exposure to the Mg-Fe-LDH NPs. In contrast, a U-shaped trend of Aodex production was observed after exposure to NPs at a concentration of 10 μg/L-100 mg/L, which was due to competition between Mg-Fe-LDH NP adsorption on Aodex and the promotion of Aodex expression by the NPs. The mechanism underling the effects of Mg-Fe-LDH NPs on A. oxidans KQ11 was investigated using a combination of physiological characterization, genomics, and transcriptomics. Exposure to 100 mg/L of Mg-Fe-LDH NPs led to NP adsorption onto Aodex, increased expression of Aodex, and generation of a new Shine-Dalgarno sequence (GGGAG) and sRNAs that both influenced the expression of Aodex. Moreover, the expressions of transcripts related to ferric iron metabolic functions were significantly influenced by treatment.

CONCLUSIONS

These results provide valuable information for further investigation of the A. oxidans KQ11 response to Mg-Fe-LDH NPs and will aid in achieving improved marine dextranase production, and even improve such activities in other marine microorganisms.

Treatment of antibiotic-resistant bacteria by encapsulation of ZnO nanoparticles in an alginate biopolymer: Insights into treatment mechanisms

Treating multidrug-resistant bacteria has been a challenging task, although the bacteria have been reported as a trace contaminant present in tap water. Given emerging issues on antibiotic-resistant bacteria, the present study investigated a novel treatment method in which ZnO nanoparticles (NPs) are encapsulated in an alginate biopolymer solution to explore primary antibacterial mechanisms. The antibacterial effects of this technology on two model antibiotic-resistant bacteria (Escherichia coli DH5-α and Pseudomonas aeruginosa) were found to be highly effective, with the removal rates of 98% and 88%, respectively, at the initial bacteria concentration of 10⁸ CFU mL^-1 over 6 h. The inactivation of antibiotic-resistant bacteria by ZnO NP-alginate beads was improved by increasing the nanocomposite amount (4, 10, and 20 mg) and contact time. The primary mechanism involved the generation of reactive oxygen species (ROS). The ZnO NP-alginate beads were demonstrated to be highly promising for different applications in water treatment, especially for point-of-use in the perspectives of reusability, antibacterial property of ZnO, immobilizing NPs, and utilizing high surface area of NPs, with a slight release of zinc ions.

In Situ Synthesis of a Silver-Containing Superabsorbent Polymer via a Greener Method Based on Carboxymethyl Celluloses

An antibacterial superabsorbent polymer (SAP) was synthesized by grafting acrylic acid (AA) onto carboxymethyl cellulose (CMC) and mixing with silver particles, with N,N'-methylenebisacrylamide used as a crosslinker and potassium persulfate as an initiator. Silver nanoparticles were produced through the reaction between glucose and silver nitrate. The effects of the amount of silver nitrate added in the polymer on the swelling ratio were investigated and the maximum swelling ratio of the SAP loaded with silver particles in distilled water and in a 0.9 wt % NaCl solution reached 840 g/g and 71 g/g, respectively, when the silver nitrate added was 50 mg. The SAP was characterized by Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, ultraviolet-visible spectroscopy, scanning electron microscopy, energy dispersive spectrometry, transmission electron microscopy, and thermogravimetric analysis. Through these analysis methods, it could be seen that the acrylic acid was successfully grafted onto CMC, forming a three-dimensional network structure, with the successful production of silver nanoparticles with sizes ranging from 5 nm to 50 nm. Moreover, the antibacterial properties of the SAP loaded with silver nanoparticles against Staphylococcus aureus and Escherichia coli were investigated and the results show that they became more effective with increasing silver nitrate concentration. The obtained SAP can be useful in developing new antibacterial medical and public health supplies.