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1. Titanium Oxide Nanoparticles as Emerging Aquatic Pollutants: An Evaluation of the Nanotoxicity in the Freshwater Shrimp Larvae Atya lanipes

   https://doi.org/10.3390/ecologies4010011  

   Cruz-Rosa, Stefani; Pérez-Reyes, Omar (March 2023, Ecologies)

   Nanoparticles are man-made materials defined as materials smaller than 100 nm in at least one dimension. Titanium oxide nanoparticles are of great interest because of their extensive use in self-care products. There is a lack of nanotoxicological studies of TiO2 NPs in benthic organisms to have evidence about the effects of these pollutants in freshwater ecosystems. Atya lanipes is a scraper/filter that can provide a good nanotoxicological model. This study aims to determine how the TiO2 NPs can develop a toxic effect in the larvae of the Atya lanipes shrimp and to document lethal and sublethal effects after acute exposures to TiO2 NP suspensions of: 0.0, 1.0, 10.0, 50.0, 100.0, and 150.0 mg/L. The results show that early exposure to TiO2 NPs in Atya lanipes creates an increase in mortality at 48 and 72 h exposures, hypoactivity in movements, and morphological changes, such as less pigmentation and the presence of edema in exposed larvae. In conclusion, TiO2 NPs are toxic contaminants in the larval stage of the Atya lanipes. It is necessary to regulate these nanoparticles for purposes of the conservation of aquatic biodiversity, especially for freshwater shrimp larvae and likely many other larvae of filter-feeding species. 

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2. Evaluation of fluorescence-based viability stains in cells dissociated from scleractinian coral Pocillopora damicornis

   https://doi.org/10.1038/s41598-022-19586-7  

   Roger, Liza M.; Adarkwa Darko, Yaa; Bernas, Tytus; White, Frances; Olaosebikan, Monsurat; Cowen, Lenore; Klein-Seetharaman, Judith; Lewinski, Nastassja A. (September 2022, Scientific Reports)

   Abstract The application of established cell viability assays such as the commonly used trypan blue staining method to coral cells is not straightforward due to different culture parameters and different cellular features specific to mammalian cells compared to marine invertebrates. UsingPocillopora damicornisas a model, we characterized the autofluorescence and tested different fluorescent dye pair combinations to identify alternative viability indicators. The cytotoxicity of different representative molecules, namely small organic molecules, proteins and nanoparticles (NP), was measured after 24 h of exposure using the fluorescent dye pair Hoechst 33342 and SYTOX orange. Our results show that this dye pair can be distinctly measured in the presence of fluorescent proteins plus chlorophyll.P. damicorniscells exposed for 24 h to Triton-X100, insulin or titanium dioxide (TiO₂) NPs, respectively, at concentrations ranging from 0.5 to 100 µg/mL, revealed a LC50 of 0.46 µg/mL for Triton-X100, 6.21 µg/mL for TiO₂NPs and 33.9 µg/mL for insulin. This work presents the approach used to customize dye pairs for membrane integrity-based cell viability assays considering the species- and genotype-specific autofluorescence of scleractinian corals, namely: endogenous fluorescence characterization followed by the selection of dyes that do not overlap with endogenous signals. 

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3. Enhanced toxicity of environmentally transformed ZnO nanoparticles relative to Zn ions in the epibenthic amphipod Hyalella azteca

   https://doi.org/10.1039/C8EN00755A  

   Poynton, Helen C.; Chen, Chun; Alexander, Shaun L.; Major, Kaley M.; Blalock, Bonnie J.; Unrine, Jason M. (January 2019, Environmental Science: Nano)

   After release into the aquatic environment, engineered nanomaterials (ENMs) undergo complex chemical and physical transformations that alter their environmental fate and toxicity to aquatic organisms. Hyalella azteca are sediment-dwelling amphipods predicted to have a high exposure level to ENMs and have previously shown to be highly sensitive to ZnO nanoparticles (NPs). To investigate the impacts of environmentally transformed ZnO NPs and determine the route of uptake for these particles, we exposed H. azteca to ZnSO 4 , ZnO NPs, and environmental aged ZnO NPs which resulted in three types of particles: 30 nm ZnO–Zn 3 (PO 4 ) 2 core–shell structures (p8-ZnO NPs), micron scale hopeite-like phase Zn 3 (PO 4 ) 2 ·4H 2 O (p6-ZnO NPs), and ZnS nano-clusters (s-ZnO NPs). Treatments included freshwater, saltwater (3 ppt), and the presence of sediment, with a final treatment where animals were contained within mesh baskets to prevent burrowing in the sediment. Dissolution was close to 100% for the pristine ZnO NPs and phosphate transformed NPs, while s-ZnO NPs resulted in only 20% dissolution in the water only exposures. In the freshwater exposure, the pristine and phosphate transformed ZnO NPs were more toxic (LC 50 values 0.11–0.18 mg L −1 ) than ZnSO 4 (LC 50 = 0.26 mg L −1 ) and the s-ZnO NPs (LC 50 = 0.29 mg L −1 ). Saltwater treatments reduced the toxicity of ZnSO 4 and all the ZnO NPs. In the presence of sediment, water column concentrations of Zn were reduced to 10% nominal concentrations and toxicity in the sediment with basket treatment was similarly reduced by a factor of 10. Toxicity was further reduced in the sediment only treatments where the sediments appeared to provide a refuge for H. azteca . In addition, particle specific differences in toxicity were less apparent in the presence of sediment. Bioaccumulation was similar across the different Zn exposures, but decreased with reduced toxicity in the saltwater and sediment treatments. Overall, the results suggest that H. azteca is exposed to ZnO NPs through the water column and NP transformations in the presence of phosphate do not reduce their toxicity. Sulfidized ZnO NPs have reduced toxicity, but their similar level of bioaccumulation in H. azteca suggests that trophic transfer of these particles will occur. 

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4. Fluorogenic Reaction Probes Defect Sites on Titanium Dioxide Nanoparticles

   Zuo, Li; Hossain, Mohammad Akter; Dubadi, Rabindra; Kist, Madelyn M.; Farhana, Fatiha; Chen, Jiao; Jaroniec, Mietek; Shen, Hao (May 2024, ChemNanoMat)

   Charlotte Liu (Ed.)

   Titanium dioxide nanoparticles (TiO2 NPs) have traditionally been utilized as industrial catalysts, finding widespread application in various chemical processes due to their exceptional stability and minimal toxicity. However, quantitatively assessing the reactive sites on TiO2 NPs remains a challenge. In this study, we employed a fluorogenic reaction to probe the apparent reactivity of TiO2 NPs. By manipulating the number of defect sites through control of hydrolysis speed and annealing temperature, we determined that the Ti(Ⅲ) content is positively correlated with the reactivity of TiO2 NPs. Additionally, these Ti(Ⅲ) sites could be introduced by reducing commercial TiO2 NPs using NaBH4. Our findings suggest that fluorogenic oxidation of Amplex Red is an effective method for probing defect site densities on TiO2 NPs. Utilizing single-molecule fluorescence imaging, we demonstrated the ability to map defect site density within TiO2 nanowires. Achieving sub-nanoparticle spatial resolution, we observed significant intraparticle and interparticle variations in the defect site distribution, leading to substantial reactivity heterogeneity. 

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5. Zero-Valent iron nanoparticles induce reactive oxygen species in the cyanobacterium, Fremyella diplosiphon.

   Gichuki, S. M. (November 2021, ACS omega)

   Dr. Krishna Ganesh (Ed.)

   Nanoscale zero-valent iron nanoparticles (nZVIs) are known to boost biomass production and lipid yield in Fremyella diplosiphon, a model biodiesel-producing cyanobacterium. However, the impact of nZVI-induced reactive oxygen species (ROS) in F. diplosiphon has not been evaluated. In the present study, ROS in F. diplosiphon strains (B481-WT and B481-SD) generated in response to nZVI-induced oxidative stress were quantified and the enzymatic response determined. Lipid peroxidation as a measure of oxidative stress revealed significantly higher malondialdehyde content (p < 0.01) in both strains treated with 3.2, 12.8, and 51.2 mg L–1 nZVIs compared to untreated control. In addition, ROS in all nZVI-treated cultures treated with 1.6–25.6 mg L–1 nZVIs was significantly higher than the untreated control as determined by the 2′,7′-dichlorodihydrofluorescein diacetate fluorometric probe. Immunodetection using densitometric analysis of iron superoxide dismutase (SOD) revealed significantly higher SOD levels in both strains treated with nZVIs at 51.2 mg L–1. In addition, we observed significantly higher (p < 0.001) SOD levels in the B481-SD strain treated with 6.4 mg L−1 nZVIs compared to 3.2 mg L–1 nZVIs. Validation using transmission electron microscopy equipped with energy-dispersive X-ray spectroscopy (EDS) revealed adsorption of nZVIs with a strong iron peak in both B481-WT and B481-SD strains. While the EDS spectra showed strong signals for iron at 4 and 12 days after treatment, a significant decrease in peak intensity was observed at 20 days. Future efforts will be aimed at studying transduction mechanisms that cause metabolic and epigenetic alterations in response to nZVIs in F. diplosiphon. 

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