Pre-exposure to Fe₂O₃ or TiO₂ Nanoparticles Inhibits Subsequent Biological Uptake of ⁵⁵Fe-Labeled Fe₂O₃ Nanoparticles

Aquatic organisms are frequently exposed to various nanoparticles (NPs) in the natural environment. Thus, studies of NP bioaccumulation should include organisms that have been previously exposed to NPs. Our study investigated the effects of pre-exposure of Tetrahymena thermophila (T. thermophila) to Fe2O3 or TiO2 NPs on the protozoan’s subsequent uptake of 55Fe-labeled Fe2O3 (55Fe2O3) NPs. Molecular mechanisms underlying the pre-exposure effects were explored in transcriptomic and metabolomic experiments. Pre-exposure to either NPs inhibited the subsequent uptake of 55Fe2O3 NPs. The results of the transcriptomic experiment indicated that NP pre-exposure influenced the expression of genes related to phagosomes and lysosomes and physiological processes such as glutathione and lipid metabolism, which are closely associated with the endocytosis of 55Fe2O3 NPs. The differentially expressed metabolites obtained from the metabolomic experiments showed an enrichment of energy metabolism and antioxidation pathways in T. thermophila pre-exposed to NPs. Together, these results demonstrate that the pre-exposure of T. thermophila to Fe2O3 or TiO2 NPs inhibited the protozoan’s subsequent uptake of 55Fe2O3 NPs, possibly by mechanisms involving the alteration of endocytosis-related organelles, the induction of oxidative stress, and a lowering of the intracellular energy supply. Thus, NP pre-exposure represents a scenario which can inform increasingly realistic estimates of NP bioaccumulation

Pre-exposure to Fe₂O₃ or TiO₂ Nanoparticles Inhibits Subsequent Biological Uptake of ⁵⁵Fe-Labeled Fe₂O₃ Nanoparticles

Aquatic organisms are frequently exposed to various nanoparticles (NPs) in the natural environment. Thus, studies of NP bioaccumulation should include organisms that have been previously exposed to NPs. Our study investigated the effects of pre-exposure of Tetrahymena thermophila (T. thermophila) to Fe2O3 or TiO2 NPs on the protozoan’s subsequent uptake of 55Fe-labeled Fe2O3 (55Fe2O3) NPs. Molecular mechanisms underlying the pre-exposure effects were explored in transcriptomic and metabolomic experiments. Pre-exposure to either NPs inhibited the subsequent uptake of 55Fe2O3 NPs. The results of the transcriptomic experiment indicated that NP pre-exposure influenced the expression of genes related to phagosomes and lysosomes and physiological processes such as glutathione and lipid metabolism, which are closely associated with the endocytosis of 55Fe2O3 NPs. The differentially expressed metabolites obtained from the metabolomic experiments showed an enrichment of energy metabolism and antioxidation pathways in T. thermophila pre-exposed to NPs. Together, these results demonstrate that the pre-exposure of T. thermophila to Fe2O3 or TiO2 NPs inhibited the protozoan’s subsequent uptake of 55Fe2O3 NPs, possibly by mechanisms involving the alteration of endocytosis-related organelles, the induction of oxidative stress, and a lowering of the intracellular energy supply. Thus, NP pre-exposure represents a scenario which can inform increasingly realistic estimates of NP bioaccumulation

Algal Foods Reduce the Uptake of Hematite Nanoparticles by Downregulating Water Filtration in <i>Daphnia magna</i>

Rapid developments in nanotechnology have led to the release of substantial amounts of nanoparticles (NPs) into aquatic environments, where many types of biotic particles are present and could potentially interact with the NPs. Nevertheless, how biotic particles may affect the bioaccumulation and toxicity of NPs remains largely unknown. In the present study, we investigated the effects of the green alga Chlamydomonas reinhardtii on the accumulation kinetics (uptake, assimilation, efflux) and toxicity of polyacrylate-coated hematite NPs (HemNPs), using Daphnia magna as the test organism. As a biotic particle and daphnid food, C. reinhardtii reduced the accumulation and toxicity of HemNPs in D. magna. The HemNPs were well-dispersed with little adsorption to the alga. Their decreased accumulation could thus be partly explained by their low trophic transfer from the alga to the daphnid and by the inductive effects of the alga on HemNP efflux. However, the main cause was the direct inhibition of HemNP uptake from the water phase as a result of the reduced water-filtration activity of D. magna in the presence of C. reinhardtii. Overall, in bioaccumulation studies, the inhibitory effects of biotic particles on NP uptake from the water phase should be paid attention

Polystyrene Nanoplastics Inhibit the Transformation of Tetrabromobisphenol A by the Bacterium <i>Rhodococcus jostii</i>

Microplastics (MPs) and nanoplastics (NPs) in the environment pose significant risks to organisms of different trophic levels. While the toxicity of MPs and NPs have been extensively investigated, it remains unknown whether these particles affect microbial transformation of organic pollutants. Here, we show that 20 and 100 nm polystyrene NPs (PS-NPs) can inhibit the transformation of tetrabromobisphenol A (TBBPA) by Gram-positive bacterium Rhodococcus jostii in a concentration-dependent manner. We found that smaller PS-NPs were more inhibitory than larger ones and that both PS-NPs affected biotransformation in several ways. PS-NPs adsorbed TBBPA on their surface and reduced the bioavailable concentration of TBBPA for transformation by R. jostii. Furthermore, PS-NPs induced oxidative stress, increased membrane permeability, and downregulated O-methyltransferase enzymes that transform TBBPA into their methylated derivatives. Our results demonstrate that PS-NPs can impact microbial transformation of organic pollutants, and these effects should be accounted for in future environmental risk assessments

Polystyrene Nanoplastics Inhibit the Transformation of Tetrabromobisphenol A by the Bacterium <i>Rhodococcus jostii</i>

Microplastics (MPs) and nanoplastics (NPs) in the environment pose significant risks to organisms of different trophic levels. While the toxicity of MPs and NPs have been extensively investigated, it remains unknown whether these particles affect microbial transformation of organic pollutants. Here, we show that 20 and 100 nm polystyrene NPs (PS-NPs) can inhibit the transformation of tetrabromobisphenol A (TBBPA) by Gram-positive bacterium Rhodococcus jostii in a concentration-dependent manner. We found that smaller PS-NPs were more inhibitory than larger ones and that both PS-NPs affected biotransformation in several ways. PS-NPs adsorbed TBBPA on their surface and reduced the bioavailable concentration of TBBPA for transformation by R. jostii. Furthermore, PS-NPs induced oxidative stress, increased membrane permeability, and downregulated O-methyltransferase enzymes that transform TBBPA into their methylated derivatives. Our results demonstrate that PS-NPs can impact microbial transformation of organic pollutants, and these effects should be accounted for in future environmental risk assessments

Polystyrene Nanoplastics Inhibit the Transformation of Tetrabromobisphenol A by the Bacterium <i>Rhodococcus jostii</i>

Microplastics (MPs) and nanoplastics (NPs) in the environment pose significant risks to organisms of different trophic levels. While the toxicity of MPs and NPs have been extensively investigated, it remains unknown whether these particles affect microbial transformation of organic pollutants. Here, we show that 20 and 100 nm polystyrene NPs (PS-NPs) can inhibit the transformation of tetrabromobisphenol A (TBBPA) by Gram-positive bacterium Rhodococcus jostii in a concentration-dependent manner. We found that smaller PS-NPs were more inhibitory than larger ones and that both PS-NPs affected biotransformation in several ways. PS-NPs adsorbed TBBPA on their surface and reduced the bioavailable concentration of TBBPA for transformation by R. jostii. Furthermore, PS-NPs induced oxidative stress, increased membrane permeability, and downregulated O-methyltransferase enzymes that transform TBBPA into their methylated derivatives. Our results demonstrate that PS-NPs can impact microbial transformation of organic pollutants, and these effects should be accounted for in future environmental risk assessments

Two self-assembled supramolecular solar cells sensitized via axial coordination with zinc porphyrin

In this work, two new self-assemblies based on zinc porphyrins substituted at the meso-positions with different donor units (denoted as ZnP1 and ZnP2) and anchor porphyrin (ZnPA) dyads formed by the coordination bonds of Zn-to-ligand have been prepared. Further, the assemblies were absorbed on semiconducting TiO2 electrode surfaces by the carboxylic groups of anchor porphyrin (ZnPA), and their photovoltaic performances in solar cells were performed under 100 mW cm−2 AM 1.5G sunlight. Photoelectrochemical studies reveal a significantly improved photovoltaic behavior for the dyad of triphenylamine-based zinc porphyrin (ZnP1) compared to the dyad with trimethylamine-based zinc porphyrin. The results were verified by electrochemical impedance spectroscopy, calculations, and optical performance. In addition, the modes of the assemblies immobilized on TiO2 electrode surfaces were also verified by transmission electron microscopy.</p