Mechanisms of ZnO Nanoparticles Enhancing Phototransformation of Biologically Derived Organic Phosphorus in Aquatic Environments

Eco-friendly fabrication of Zn-based nanoparticles: implications in agricultural advancement and elucidation of toxicity aspects

Zinc (Zn) is a vital micronutrient required for optimal plant growth and soil fertility. Its use in the form of nanoparticles (NPs) has gained significant attention in agricultural applications. Green synthesized Zn-based NPs offer an eco-friendly solution to several conventional problems in agriculture. Several plants, bacteria, fungi and yeast have shown significant potential in fabricating Zn NPs that can provide environmentally friendly solutions in agriculture and the approach is aligned with sustainable agricultural practices, reducing the dependency on harmful agrochemicals. Zn-based NPs act as plant growth promoters, enhance crop yield, promote resilience to abiotic stressors and are efficient crop protection agents. Their role as a smart delivery system, enabling targeted and controlled release of agrochemicals, further signifies their potential use in agriculture. Because agriculture requires repeated applications hence, the toxicological aspects of Zn NPs cannot be ignored. Zn NPs are reported to cause phytotoxicity, including root damage, physiological and biochemical disturbances, and genotoxic effects. Furthermore, exposure to Zn NPs poses risks to soil microbiota, and aquatic and terrestrial organisms potentially impacting the ecosystem. The green synthesis of Zn-based NPs has a promising aspect for advancing sustainable agriculture by reducing agrochemical use and improving crop productivity. Their diverse applications as plant growth promoters, crop protectants and smart delivery systems emphasize their potential. However, the toxicological aspects are essential to ensure the standardization of doses for their safe and effective use. Further research would help address such concerns and help in developing viable and eco-friendly solutions for modern agriculture. © 2025 Society of Chemical Industry.

Key events relating to homeostasis and regeneration of freshwater planarians (Dugesia Japonica) after exposure to various ZnO-forms

This study aims to investigate the toxicity and underlying mechanisms of ZnO nanoparticles (ZnO NPs), bulk ZnO (ZnO MPs), and zinc ions (Zn2 +) on Dugesia japonica planarians, with a focus on their bioaccumulation, transformation, and associated biological effects. Using advanced techniques such as synchrotron X-ray fluorescence (XRF), X-ray Absorption Near Edge Structure (XANES) and single particle ICP-MS (sp-ICP-MS), we measured the accumulation, distribution, and transformation of these materials in planarians. All treatments caused significant Zn accumulation: ZnO NPs increased Zn by 120-fold, ZnO MPs by 100-fold, and Zn2+ by 430-fold. XANES and sp-ICP-MS analysis confirmed that ZnO NPs remained largely in particulate form (40-60 %) following uptake by planarians. Toxicity tests revealed that all treatments impaired blastema growth, locomotion, stem cell proliferation, differentiation, and neural regeneration. ZnO MPs exhibited higher toxicity than ZnO NPs, while Zn2+ resulted in elevated oxidative stress. ZnO NPs induced severe energy damage and triggered cell apoptosis, whereas ZnO MPs caused more pronounced necrosis cell death. Transcriptomic and proteomic analyses showed that all treatments disrupted pathways related to oxidative stress response, energy metabolism and cell apoptosis. ZnO NPs primarily affected the membrane integrity pathway, ZnO MPs altered cell homeostasis and membrane potential, while Zn2+ exposure triggered metal ion-specific cellular reactions. These molecular and cellular changes collectively explain the observed phenotypic outcomes, which align with the Adverse Outcome Pathway framework. The findings provide insights into the environmental risks of different ZnO forms and highlight their distinct toxicity mechanisms.

Green synthesis of zinc oxide nanoparticles using Cnidium monnieri fruit extract: Prescription optimization, Characterization and antifungal activity

Currently, the drugs employed to treat superficial fungal infections are encountering challenges, particularly the rise of drug resistance. Numerous studies have suggested that zinc oxide nanoparticles (ZnO NPs) show promise in the realm of antifungal treatment. Green synthesis makes the preparation of ZnO NPs more environmentally friendly and economical. In order to prepare antifungal active nanoparticles with low economic cost and stable performance, zinc oxide nanoparticles (CM-ZnONPs) were synthesized for the first time in this study using zinc sulfate heptahydrate (ZnSO4·7H2O) with a Cnidium monnieri (L.) Cuss. (C. monnieri) fruit extract as a reducing agent. In this study, the Box-Behnken design method was used to optimize the manufacturing process of CM-ZnONP. Various techniques, including UV-vis, Fourier Transform Infrared Spectroscopy (FTIR) and X-ray Powder Diffraction (XRD) were employed to demonstrate the successful preparation of CM-ZnONPs. The Transmission Electron Microscopy (TEM) analysis indicated that the size of CM-ZnONPs was 53.30 ± 12.89 nm. The dynamic light scattering (DLS) analysis showed the size of 157.7 ± 15.57 nm for CM-ZnONPs, along with an average polydispersity index (PDI) of 0.1791 ± 0.1394. The zone of inhibition of CM-ZnONPs against Candida albicans (C. albicans) was demonstrated to be 17.0 ± 0.8 mm by paper diffusion experiments. The minimum inhibitory concentration (MIC) of CM-ZnONPs against C. albicans was established at 58.59 μg/mL through the microdilution method. In summary, CM-ZnONPs exhibit excellent performance and antifungal activity in various properties. It is expected to be widely produced and used as an effective treatment for superficial fungal infections.

ZnO Nanofertilizer Reduced Organic Phosphorus Transformation and Altered Microbial Function in Soil for Sustainable Agriculture

The impacts of zinc oxide nanoparticles (ZnO NPs) as nanofertilizers on the transformation of phytogenic organic phosphorus (OP), specifically phytic acid (PA) and soy lecithin (LE), as well as their effects on soil microbial functions, remain insufficiently characterized. This study employed a 60-day soil microuniverse experiment to investigate microbial responses to OP under ZnO NPs exposure, focusing on soil physicochemical properties, phosphorus (P) and Zn species transformations, bacterial community and function. At low concentrations (5 and 20 mg/kg), ZnO NPs did not significantly reduce the available P content, but they reduced the transformation of OP into other P species. Synchrotron-based X-ray absorption near-edge spectroscopy revealed that ZnO NPs increased the relative abundance of PA from 0.6 to 3.5% and LE from 58.4 to 67.1%. Bacterial community composition was influenced by P species rather than ZnO NPs concentration. A coupled biogeochemical cycle among carbon, nitrogen and P was observed, with higher total phosphorus further enhancing the abundance of genes involved in P-related processes, such as OP mineralization genes, which increased 6-, 4-, and 2-fold in PAZ5, LEZ5, and PiZ5, respectively, compared to Z5. Carbon fixation genes generally increased in the P-added groups, exemplified by atoB, which encodes acetoacetyl-CoA thiolase, showing a 3.70-, 3.05-, and 3.47-fold increase compared to Z5. In contrast, denitrification genes, nirS, decreased by 0.08-, 0.10-, and 0.33-fold. These findings shed light on the fate of ZnO nanofertilizers and P, supporting the sustainable application of nanofertilizers and the improvement of soil fertility.

Screening of metal-modified biochars for practical phosphorus recovery

The utilization of metal-modified biochars (MBCs) for practical phosphorus recovery has attracted significant research interest recently. However, the optimal choice of metals and modification methods for MBCs remains unclear. This study addresses this gap by comparing the phosphate adsorption capabilities of various MBCs using real municipal wastewater. The results show that zinc-modified biochar exhibits superior phosphate adsorption compared to biochars modified with calcium, magnesium, aluminum, and iron. Specifically, zinc-modified biochar prepared through metal-mediated biomass pyrolysis with alkaline soaking (ZnBC-OH) demonstrates the highest adsorption capacity, achieving 36.6 mg P/g in wastewater with a phosphate concentration of 5 mg P/L. This performance surpasses that of previously reported non-lanthanide modified biochars and is comparable to lanthanide-modified biochars. Mechanistic investigations reveal that the exceptional performance of ZnBC-OH is due to the presence of highly dispersed ZnO sites, which facilitate the formation of Zn3(PO4)2·4H2O precipitation, effectively retaining phosphate. Furthermore, a techno-economic analysis indicates that using ZnBC-OH in a fixed-bed column system can reduce phosphate levels from 6 mg L-1 to below 0.5 mg L-1 at a cost of 1.834 USD per ton of secondary treated wastewater, underscoring its promising application potential.

Photoperiod-dependent effects of zinc oxide nanoparticles on the growth and reproduction of Daphnia pulex

The discharge of metal nanoparticles into the water inevitably poses a threat to aquatic organisms and the balance of the aquatic ecosystem. Photoperiod is one of the most important ecological factors for the development of cladocerans. In addition, different light conditions can also affect the toxicity of metal nanoparticles. In this study, we studied the effects of four photoperiods (8L/16D, 10L/14D, 14L/10D, and 16L/8D) combined with three concentrations of ZnO NPs (0 mg L-1, 0.05 mg L-1, and 0.10 mg L-1) on the growth and reproduction of Daphnia pulex. With the increase of photoperiod, the maternal body size and growth rate increased first and then decreased; the first time to reproduction was advanced, and broods and the total offspring also increased. Under the influence of ZnO NPs, growth rate and reproductive capacity were inhibited. The photoperiod 8L/16D and 16L/8D interacted with ZnO NPs on the growth of D. pulex, which significantly decreased the growth rate. Besides, the interaction between photoperiod 8L/16D and ZnO NPs decreased the reproduction ability of D. pulex. These results suggest that the effects of zinc oxide nanoparticles on the growth and reproduction of D. pulex is photoperiod dependent, which is useful for assessing the risk of pollutants to cladoceras under different light conditions.

Cutting-edge developments in zinc oxide nanoparticles: synthesis and applications for enhanced antimicrobial and UV protection in healthcare solutions

This paper presents a comprehensive review of recent advancements in utilizing zinc oxide nanoparticles (ZnO NPs) to enhance antimicrobial and UV protective properties in healthcare solutions. It delves into the synthesis techniques of ZnO NPs and elucidates their antimicrobial efficacy, exploring the underlying mechanisms governing their action against a spectrum of pathogens. Factors impacting the antimicrobial performance of ZnO NPs, including size, surface characteristics, and environmental variables, are extensively analyzed. Moreover, recent studies showcasing the effectiveness of ZnO NPs against diverse pathogens are critically examined, underscoring their potential utility in combatting microbial infections. The study further investigates the UV protective capabilities of ZnO NPs, elucidating the mechanisms by which they offer UV protection and reviewing recent innovations in leveraging them for UV-blocking applications in healthcare. It also dissects the factors influencing the UV shielding performance of ZnO NPs, such as particle size, dispersion quality, and surface coatings. Additionally, the paper addresses challenges associated with integrating ZnO NPs into healthcare products and presents future perspectives for overcoming these hurdles. It emphasizes the imperative for continued research efforts and collaborative initiatives to fully harness the potential of ZnO NPs in developing advanced healthcare solutions with augmented antimicrobial and UV protective attributes. By advancing our understanding and leveraging innovative approaches, ZnO NPs hold promise for addressing pressing healthcare needs and enhancing patient care outcomes.

Deciphering the Impact of ZnO Nanoparticles and a Sunscreen Product Containing ZnO on Phosphorus Dynamics and Release in Chlorella pyrenoidosa in Aquatic Systems

Zinc oxide nanoparticles (ZnO NPs) expedite the conversion of organic phosphorus (OP) into PO4-P (Pi), facilitating phosphorus (P) absorption by algae. Our study explored the mechanisms of converting OP (2-aminoethylphosphonic acid (AEP) and β-glycerol phosphate (β-GP)) into Pi in Chlorella pyrenoidosa under P deficiency with sunscreen and ZnO NPs. Cell density followed the order of K2HPO4 > β-GP+ZnO > β-GP > AEP+ZnO > AEP > P-free. ZnO NPs promoted the conversion of β-GP, containing C-O-P bonds (0.028-0.041 mg/L), into Pi more efficiently than AEP, which possesses C-P bonds (0.022-0.037 mg/L). Transcriptomics revealed Pi transport/metabolism (phoB (3.99-12.01 fold), phoR (2.20-5.50 fold), ppa (4.49-10.40 fold), and ppk (2.50-5.40 fold)) and phospholipid metabolism (SQD1 (1.85-2.79 fold), SQD2 (2.60-6.53 fold), MGD (2.13-3.21 fold), and DGD (4.08-7.56 fold)) were up-regulated compared to K2HPO4. 31P nuclear magnetic resonance spectroscopy identified intracellular P as polyphosphate, orthophosphate, and pyrophosphate. Synchrotron radiation-based X-ray near-edge structure spectroscopy indicated that K2HPO4 and Zn3(PO4)2 in β-GP+ZnO were increased by 8.09% and 7.28% compared to AEP+ZnO, suggesting superior P storage in β-GP+ZnO. Overall, ZnO NPs improved photoinduced electron-hole pair separation and charge separation efficiency and amplified the ·OH and ·O2- levels, promoting OP photoconversion into Pi and algae growth.

Green approach for the fabrication of dual-functional S/N doped graphene tagged ZnO nanograins for in vitro bioimaging and water pollutant remediation

Dual-functional S/N (sulfur and nitrogen) doped graphene-tagged zinc oxide nanograins were synthesized for bioimaging applications and light-dependent photocatalytic activity. Applying the green synthesis approach, graphene was synthesized from kimchi cabbage through a hydrothermal process followed by tagging it with synthesized zinc oxide nanoparticles (ZnO-NPs). The 2D/0D heterostructure prepared by combining both exhibited exceptional advantages. Comprehensive characterizations such as TEM, SEM, XRD, FTIR, XPS, and UV-Vis spectra have been performed to confirm the structures and explore the properties of the synthesized nanocomposite. The graphene/ZnO-NP composite produced exhibited more intense fluorescence, greater chemical stability and biocompatibility, lower cytotoxicity, and better durability than ZnO NPs conferring them with potential applications in cellular imaging. While tagging the ZnO NPs with carbon derived from a natural source containing hydroxyl, sulfur, and nitrogen-containing functional group, the S/N doped graphene/ZnO heterostructure evidences the high photocatalytic activity under UV and visible irradiation which is 3.2 and 3.8 times higher than the as-prepared ZnO-NPs. It also demonstrated significant antibacterial activity which confers its application in removing pathogenic contaminant bacteria in water bodies. In addition, the composite had better optical properties and biocompatibility, and lower toxicity than ZnO NPs. Our findings indicate that the synthesized nanocomposite will be suitable for various biomedical and pollutant remediation due to its bright light-emitting properties and stable fluorescence.

Effects of Zinc Oxide Nanoparticles on Growth, Development, and Flavonoid Synthesis in Ginkgo biloba

Ginkgo biloba is a highly valuable medicinal plant known for its rich secondary metabolites, including flavonoids. Zinc oxide nanoparticles (ZnO-NPs) can be used as nanofertilizers and nano-growth regulators to promote plant growth and development. However, little is known about the effects of ZnO-NPs on flavonoids in G. biloba. In this study, G. biloba was treated with different concentrations of ZnO-NPs (25, 50, 100 mg/L), and it was found that 25 mg/L of ZnO-NPs enhanced G. biloba fresh weight, dry weight, zinc content, and flavonoids, while 50 and 100 mg/L had an inhibitory effect on plant growth. Furthermore, quantitative reverse transcription (qRT)-PCR revealed that the increased total flavonoids and flavonols were mainly due to the promotion of the expression of flavonol structural genes such as GbF3H, GbF3'H, and GbFLS. Additionally, when the GbF3H gene was overexpressed in tobacco and G. biloba calli, an increase in total flavonoid content was observed. These findings indicate that 25 mg/L of ZnO-NPs play a crucial role in G. biloba growth and the accumulation of flavonoids, which can potentially promote the yield and quality of G. biloba in production.

Phototransformation of phosphite induced by zinc oxide nanoparticles (ZnO NPs) in aquatic environments

Phosphite, an essential component in the biogeochemical phosphorus cycle, may make significant contributions to the bioavailable phosphorus pool as well as water eutrophication. However, to date, the potential impacts of coexisting photochemically active substances on the environmental fate and transformation of phosphite in aquatic environments have been sparsely elucidated. In the present study, the effect of zinc oxide nanoparticles (ZnO NPs), a widely distributed photocatalyst in aquatic environments, on phosphite phototransformation under simulated solar irradiation was systematically investigated. The physicochemical characteristics of the pristine and reacted ZnO NPs were thoroughly characterized. The results showed that the presence of ZnO NPs induced the indirect phototransformation of phosphite to phosphate, and the reaction rate increased with increasing ZnO NPs concentration. Through experiments with quenching and trapping free radicals, it was proved that photogenerated reactive oxygen species (ROS), such as hydroxyl radical (•OH), superoxide anion (O2•-), and singlet oxygen (1O2), made substantial contributions to phosphite phototransformation. In addition, the influencing factors such as initial phosphite concentration, pH, water matrixes (Cl-, F-, Br-, SO42-, NO3-, NO2-, HCO3-, humic acid (HA) and citric acid (CA)) were investigated. The component of generated precipitates after the phosphite phototransformation induced by ZnO NPs was still dominated by ZnO NPs, while the presence of amorphous Zn3(PO4)2 was identified. This work explored ZnO NPs-mediated phosphite phototransformation processes, indicating that nanophotocatalysts released into aquatic environments such as ZnO NPs may function as photosensitizers to play a beneficial role in the transformation of phosphite to phosphate, thereby potentially mitigating the toxicity of phosphite to aquatic organisms while exacerbating eutrophication. The findings of this study provide a novel insight into the comprehensive assessment of the environmental fate, potential ecological risk, and biogeochemical behaviors of phosphite in natural aquatic environments under the condition of combined pollution.