Zn2+ leakage and photo-induced reactive oxidative species do not explain the full toxicity of ZnO core Quantum Dots

Visible-light-driven water-soluble zinc oxide quantum dots for efficient control of citrus canker

BACKGROUND

Citrus canker caused by Xanthomonas citri subsp. citri (Xcc) is a devastating bacterial disease that reduces citrus yield and quality, posing a serious threat to the citrus industry. Several conventional chemicals have been used to control citrus canker. However, this approach often leads to the excessive use of chemical agents, can exacerbate environmental pollution and promotes the development of resistant Xcc. Therefore, there is significant interest in the development of efficient and environmentally friendly technologies to control citrus canker.

RESULTS

In this study, water-soluble ZnO quantum dots (ZnO QDs) were synthesised as an efficient nanopesticide against Xcc. The results showed that the antibacterial activity of ZnO QDs irradiated with visible light [half-maximal effective concentration (EC50) = 33.18 μg mL-1] was ~3.5 times higher than that of the dark-treated group (EC50 = 114.80 μg mL-1). ZnO QDs induced the generation of reactive oxygen species (•OH, •O- 2 and 1O2) under light irradiation, resulting in DNA damage, cytoplasmic destruction, and decreased catalase and superoxide dismutase activities. Transcription analysis showed downregulation of Xcc genes related to 'biofilms, virulence, adhesion' and 'DNA transfer' exposure to ZnO QDs. More importantly, ZnO QDs also promoted the growth of citrus.

CONCLUSION

This research provides new insights into the photocatalytic antibacterial mechanisms of ZnO QDs and supports the development of more efficient and safer ZnO QDs-based nanopesticides to control citrus canker. © 2024 Society of Chemical Industry.

Polydopamine-Coated Copper-Doped Co3O4 Nanosheets Rich in Oxygen Vacancy on Titanium and Multimodal Synergistic Antibacterial Study

Medical titanium-based (Ti-based) implants in the human body are prone to infection by pathogenic bacteria, leading to implantation failure. Constructing antibacterial nanocoatings on Ti-based implants is one of the most effective strategies to solve bacterial contamination. However, single antibacterial function was not sufficient to efficiently kill bacteria, and it is necessary to develop multifunctional antibacterial methods. This study modifies medical Ti foils with Cu-doped Co3O4 rich in oxygen vacancies, and improves their biocompatibility by polydopamine (PDA/Cu-Ov-Co3O4). Under near-infrared (NIR) irradiation, nanocoatings can generate •OH and 1O2 due to Cu+ Fenton-like activity and a photodynamic effect of Cu-Ov-Co3O4, and the total reactive oxygen species (ROS) content inside bacteria significantly increases, causing oxidative stress of bacteria. Further experiments prove that the photothermal process enhances the bacterial membrane permeability, allowing the invasion of ROS and metal ions, as well as the protein leakage. Moreover, PDA/Cu-Ov-Co3O4 can downregulate ATP levels and further reduce bacterial metabolic activity after irradiation. This coating exhibits sterilization ability against both Escherichia coli and Staphylococcus aureus with an antibacterial rate of ca. 100%, significantly higher than that of bare medical Ti foils (ca. 0%). Therefore, multifunctional synergistic antibacterial nanocoating will be a promising strategy for preventing bacterial contamination on medical Ti-based implants.

Fe3 O4 nanozyme coating enhances light-driven biohydrogen production in self-photosensitized Shewanella oneidensis-CdS hybrid systems

Solar-driven biohybrid systems that produce chemical energy are a valuable objective in ongoing research. However, reactive oxygen species (ROS) that accompany nanoparticle production under light radiation severely affect the efficiency of biohybrid systems. In this study, we successfully constructed a two-hybrid system, Shewanella oneidensis-CdS and S. oneidensis-CdS@Fe3 O4 , in a simple, economical, and gentle manner. With the Fe3 O4 coating, ROS were considerably eliminated; the hydroxyl radical, superoxide radical, and hydrogen peroxide contents were reduced by 66.7%, 65.4%, and 72%, respectively, during light-driven S. oneidensis-CdS hydrogen production. S. oneidensis-CdS@Fe3 O4 showed a 2.6-fold higher hydrogen production (70 h) than S. oneidensis-CdS. Moreover, the S. oneidensis-CdS system produced an additional 367.8 μmol g-dcw-1 (70 h) of hydrogen compared with S. oneidensis during irradiation. The apparent quantum efficiencies of S. oneidensis-CdS and S. oneidensis-CdS@Fe3 O4 were 6.2% and 11.5%, respectively, exceeding values previously reported. In conclusion, a stable nanozyme coating effectively inhibited the cytotoxicity of CdS nanoparticles, providing an excellent production environment for bacteria. This study provides a rational strategy for protecting biohybrid systems from ROS toxicity and contributes to more efficient solar energy conversion in the future.

Microalga Broths Synthesize Antibacterial and Non-Cytotoxic Silver Nanoparticles Showing Synergy with Antibiotics and Bacterial ROS Induction and Can Be Reused for Successive AgNP Batches

The era of increasing bacterial antibiotic resistance requires new approaches to fight infections. With this purpose, silver-based nanomaterials are a reality in some fields and promise new developments. We report the green synthesis of silver nanoparticles (AgNPs) using culture broths from a microalga. Broths from two media, with different compositions and pHs and sampled at two growth phases, produced eight AgNP types. Nanoparticles harvested after several synthesis periods showed differences in antibacterial activity and stability. Moreover, an evaluation of the broths for several consecutive syntheses did not find relevant kinetics or activity differences until the third round. Physicochemical characteristics of the AgNPs (core and hydrodynamic sizes, Z-potential, crystallinity, and corona composition) were determined, observing differences depending on the broths used. AgNPs showed good antibacterial activity at concentrations producing no or low cytotoxicity on cultured eukaryotic cells. All the AgNPs had high levels of synergy against Escherichia coli and Staphylococcus aureus with the classic antibiotics streptomycin and kanamycin, but with ampicillin only against S. aureus and tetracycline against E. coli. Differences in the synergy levels were also dependent on the types of AgNPs. We also found that, for some AgNPs, the killing of bacteria started before the massive accumulation of ROS.

Proteomics and Metabolomics Analysis Reveals the Toxicity of ZnO Quantum Dots on Human SMMC-7721 Cells

Purpose

ZnO quantum dots (QDs) are composed of less toxic metals than other QDs but have the same interesting photochemical properties. Thus, they have received considerable attention recently. Nevertheless, their toxicity cannot be ignored.

Methods

In this study, we incubated ZnO QDs with human SMMC-7721 cells for 24 h to assess their nanotoxicity through proteomics (Fold change >1.5 and p-value <0.05) and metabolomics (Fold change ≥ 1.5; VIP ≥ 1; p-value < 0.05) analyses.

Results

Both of 174 and 219 significantly changed metabolites were identified in human SMMC-7721 cells treated with 20 and 50 µg/mL ZnO QDs, respectively. ZnO QDs significantly modified metabolic pathways, including purine metabolism, ferroptosis, morphine addiction, alcoholism, cGMP-PKG signaling, and Cushing syndrome. Moreover, we identified 105 and 8 differentially expressed proteins in cells treated with 20 and 50 µg/mL ZnO QDs, and the pathways of alcoholism and Cushing syndrome were enriched.

Conclusion

ZnO QDs did not affect cell viability in a CCK8 assay, but disturbed the level of intracellular metabolites and proteins at 20 µg/mL. The KEGG analyses of the metabolomics and proteomics data both enriched the alcoholism and Cushing syndrome pathways. These results provide an experimental basis for future research on the safe use of nanomaterials.

Performance and mechanisms exploration of nano zinc oxide (nZnO) on anaerobic decolorization by Shewanella oneidensis MR-1

Although the ecological safety of nanomaterials is of widespread concern, their current ambient concentrations are not yet sufficient to cause serious toxic effects. Thus, the nontoxic bioimpact of nanomaterials in wastewater treatment has attracted increasing attention. In this study, the effect of nano zinc oxide (nZnO), one of the most widely used nanomaterials, on the anaerobic biodegradation of methyl orange (MO) by Shewanella oneidensis MR-1 was comprehensively investigated. High-dosage nZnO (>0.5 mg/L) caused severe toxic stress on S. oneidensis MR-1, resulting in the decrease in decolorization efficiency. However, nZnO at ambient concentrations could act as nanostimulants and promote the anaerobic removal of MO by S. oneidensis MR-1, which should be attributed to the improvement of decolorization efficiency rather than cell proliferation. The dissolved Zn²⁺ was found to contribute to the bioeffect of nZnO on MO decolorization. Further investigation revealed that low-dosage nZnO could promote the cell viability, membrane permeability, anaerobic metabolism, as well as related gene expression, indicating that nZnO facilitated rather than inhibited the anaerobic wastewater treatment under ambient conditions. Thus, this work provides a new insight into the bioeffect of nZnO in actual environment and facilitates the practical application of nanomaterials as nanostimulants in biological process.

Investigation on visible-light photocatalytic performance and mechanism of zinc peroxide for tetracycline degradation and Escherichia coli inactivation

In this study, zincperoxide (ZnO₂) with broad energy gap was firstly used for visible-light-induced photocatalytic degradation of tetracycline (TC) and inactivation of Escherichia coli (E. coli). A small amount of ZnO₂ (10 mg) could efficiently degrade 100 mL of 50 mg/L TC in a wide pH range (4-12), and the degradation performance was rarely suppressed by common matrix species and natural water sources. Also, 100 mg/L ZnO₂ could inactivate around 7-log E. coli cells within 60 min under visible-light irradiation. Quenching experiments and electron paramagnetic resonance (EPR) results confirmed that superoxide radical (•O₂^-) and singlet oxygen (¹O₂) were the main reactive oxygen species (ROS), which were attributed to the self-sensitization of TC and the photoexcitation of released H₂O₂ under the catalysis of Zn(OH)₂ from the hydrolysis of partial ZnO₂, respectively. The pathways of TC degradation and processes of visible-light-induced TC degradation and E. coli inactivation were proposed and deduced in detail. This work presented the enhanced visible-light photocatalytic activities of ZnO₂ for antibiotic degradation and bacterial inactivation, and provided a deep insight into the mechanisms of visible-light-induced TC degradation andE. coli inactivation over ZnO₂.

Current Knowledge on the Oxidative-Stress-Mediated Antimicrobial Properties of Metal-Based Nanoparticles

The emergence of multidrug-resistant (MDR) bacteria in recent years has been alarming and represents a major public health problem. The development of effective antimicrobial agents remains a key challenge. Nanotechnologies have provided opportunities for the use of nanomaterials as components in the development of antibacterial agents. Indeed, metal-based nanoparticles (NPs) show an effective role in targeting and killing bacteria via different mechanisms, such as attraction to the bacterial surface, destabilization of the bacterial cell wall and membrane, and the induction of a toxic mechanism mediated by a burst of oxidative stress (e.g., the production of reactive oxygen species (ROS)). Considering the lack of new antimicrobial drugs with novel mechanisms of action, the induction of oxidative stress represents a valuable and powerful antimicrobial strategy to fight MDR bacteria. Consequently, it is of particular interest to determine and precisely characterize whether NPs are able to induce oxidative stress in such bacteria. This highlights the particular interest that NPs represent for the development of future antibacterial drugs. Therefore, this review aims to provide an update on the latest advances in research focusing on the study and characterization of the induction of oxidative-stress-mediated antimicrobial mechanisms by metal-based NPs.

Cytotoxicity of ZnO Nanoparticle Under Dark via Oxygen Vacancy Dependent Reactive Oxygen Species Generation

Antimicrobial and cytotoxic effect of zinc oxide nanomaterials are popularly thought due to zinc ion leaching, but the exact mechanism of cytotoxicity is controversial and not fully understood. Recent works...

Impact of bovine serum albumin - A protein corona on toxicity of ZnO NPs in environmental model systems of plant, bacteria, algae and crustaceans

Zinc oxide nanoparticles (ZnO NPs) are widely applied in industrial, household and medical areas that lead to its discharge and accumulation in ecosystem. Here, the toxic effect of ZnO NPs in presence and absence of bovine serum albumin (BSA) was analyzed. The difference in toxicity of bare ZnO and BSA interacted ZnO was studied with different environmental models. P. aeruginosa and S. aureus were used as model bacterial systems. Toxicity against bacteria was determined by employing plate count method. C. pyrenoidsa was used as algal system for evaluating toxicity and it was determined by chlorophyll estimation assay. Daphnia sp. was chosen as crustacean system model. A. cepa root cells were chosen as plant model. ZnO NPs increased the ROS formation, lipid peroxidation and oxidative stress and it reduced in the presence of BSA. The cytotoxicity, chromosomal aberrations and micronuclei (MN) index of A. cepa were increased after ZnO NPs treatment. Same time the toxic effect was decreased in case of BSA coated ZnO NPs. The NPs toxic potential on the organisms decreased in the order of P. aeruginosa (LC₅₀-0.092 mg/L) > S. aureus (LC₅₀-0.33 mg/L) > Daphnia sp (LC₅₀-0.35 mg/L) > C. pyrenoidosa (LC₅₀-8.17 mg/L). LC₅₀ in presence of BSA was determined to be 18.45, 26.24, 17.27 and 53.97 mg/L for P. aeruginosa, S. aureus, Daphnia sp and C. pyrenoidosa respectively. Therefore, the report suggests that BSA stabilized ZnO NPs could be more amenable towards applications in biotechnology and bioengineering.

Metabolic Conversion and Removal of Manganese Ferrite Nanoparticles in RAW264.7 Cells and Induced Alteration of Metal Transporter Gene Expression

Background

Manganese Ferrite Nanoparticles (Mn-IONPs) are widely used in biomedical field and their cytotoxicity has been initially explored, but the mechanism remains obscure. The nano-bio interactions are believed to be crucial for cytotoxicity mechanism, while little data have been acquired.

Methods

Mn-IONPs were synthesized by thermal decomposition of acetylacetonate precursor. After physicochemical characterization, we analyzed the metabolic conversion and removal of Mn-IONPs in RAW264.7 cells by Prussian blue staining, TEM, HRTEM and elemental quantitative analysis, followed by gene expression evaluation using quantitative RT-PCR.

Results

Mn-IONPs were successfully synthesized. Both the uptake and cytotoxicity of Mn-IONPs on RAW264.7 cells were time- and dose-dependent. After internalized, Mn-IONPs were passed to daughter cells with passages on. Meanwhile, Mn-IONPs were exocytosed and digested to metal ions and further excreted out, resulted in the labeling rate and ions contents decreased gradually. As ion influx related genes, the expressions of ZIP14, IRP2, FtH and DMT1 were suppressed within 24 hours but overexpressed to a plateau at the 48th hour in a dose-dependent manner. At the 72nd hour, ZIP14 and DMT1 mRNA levels decreased toward normal, while IRP2 and FtH kept up-regulated. As efflux related genes, FPN, SLC30A10 and Hamp2 genes were up-regulated within 24–72 hours; SPCA1 was suppressed at the 24th and 72nd hour, while overexpressed at the 48th hour. All the efflux related genes’ mRNA had a dose-dependent increasing manner at the corresponding time points.

Conclusion

Mn-IONPs showed time- and dose-dependent cytotoxicity and cell labeling rate in RAW264.7 cells. Accompanying with the intracellular catabolic breakdown and exocytosis of Mn-IONPs, RAW264.7 cells also secreted and re-uptook manganese and iron ions to maintain intracellular homeostasis in the succeeding passages. And the metabolic conversion of Mn-IONPs in RAW264.7 cells can affect the expression of ZIP14, DMT1, FPN, SLC30A10, IRP2, FtH, Hamp2 and SPCA1 genes.