Internalization of the Metal-Organic Framework MIL-101(Cr)-NH2 by a Freshwater Alga and Transfer to Zooplankton

Toxic effects and action mechanism of metal-organic framework UiO-66-NH2 in Microcystisaeruginosa

The zirconium metal-organic framework UiO-66-NH2 has garnered considerable attention for their potentials of removing environmental contaminants from water. The production and application of UiO-66-NH2 make their releases into the aquatic environment inevitable. Nevertheless, little information is available regarding its potential risk to the environment and aquatic organisms, thus limiting the evaluation of its safe and sustainable use. In this study, the ecotoxicity of UiO-66-NH2 was evaluated, specifically its impacts on growth, extracellular organic matter release, and metabolomic changes of the model phytoplankton Microcystis aeruginosa (M. aeruginosa). UiO-66-NH2 exhibited moderate effects on algal physiology including growth, viability, and photosynthetic system. At concentrations below 20 mg/L, UiO-66-NH2 induced negligible inhibition of algal growth, algal viability, and photosynthesis. In contrast, UiO-66-NH2 boosted the release of extracellular organic matter even at concentration as low as 0.02 mg/L. These findings indicated that, while no evident damage to algal cells was observed, UiO-66-NH2 was hazardous to the aquatic environment as it stimulated the release of algal toxins. Moreover, UiO-66-NH2 entered algal cells rather than adhering to the surface of M. aeruginosa as observed by the fluorescence imaging. Based on metabolic analysis, UiO-66-NH2 influenced the cyanobacteria mainly through interference with purine metabolism and ABC transporter. This study sheds light on the potential threat UiO-66-NH2 posing to microalgae, and has potential implications for its safe utilization in the environmental field.

Infiltration of freshwater food chain by nanoplastics: An examination of trophic transfer and biological impact

The contamination of freshwater by nanoplastics (NPs) poses a significant threat to various organisms. However, the influence of food factors on the NPs toxicity and the associated risks to water safety remains poorly understood. In this study, we employed highly fluorescent NPs incorporating aggregation-induced emission fluorogens to quantify and visualize the interactions of NPs with freshwater phytoplanktonic alga Chlamydomonas reinhardtii and zooplankton Daphnia magna, including the uptake of NPs by algae and daphnids, as well as gut environment responses through both waterborne and foodborne routes. NPs at environmentally relevant concentrations were capable of aggregating and internalizing in planktonic algae, thus permeating the food chain and potentially causing ecological risks. Notably, positively charged NPs exhibited greater infiltration than the negatively charged NPs. Our findings indicated that NPs had a greater tendency to accumulate in Daphnia via the food chain rather than through direct exposure to water. This was attributed to the loss of selectivity, suggesting a potential mechanism for NP accumulation in aquatic food chains. However, daphnids exposed to NPs through waterborne route exhibited more gut pH acidification, esterase activity, and gut inflammation compared to those exposed via the foodborne route. Moreover, chronic exposure to NPs through waterborne routes significantly disrupted the growth, molting, and reproduction of Daphnia compared to the foodborne group. These findings provided valuable insights into the complexities of plastic pollution on primary trophic levels in aquatic environments.

How safe are nanoscale metal-organic frameworks?

Owing to the size scales that can be accessed, the nanoscale has opened doors to new physical and chemical properties, not seen in the bulk. These properties are leveraged by nanomaterials (NMs) across a plethora of applications. More recently, nanoscale metal-organic frameworks (nMOFs) have witnessed explosive growth due to the modularity of their chemical constituents, the ability to modify their composition and structure, and exceptional properties such as permanent porosity and high surface areas. These properties have prompted the investigation of these materials for applications in biological and environmental contexts. However, one aspect that is often ignored in these discussions is their safety at a nanoscale. In this mini review, we aim to initiate a discussion on the safety and toxicity of nMOFs, drawing parallels with the existing guidelines and literature on the safety of inorganic NMs. We first describe why nMOFs are of considerable interest to the scientific community followed by a discussion on routes through which they can be exposed to the environment and living organisms, particularly shedding light on their transformation mechanisms. The review also discusses the factors affecting toxicity of nMOFs, such as their size, shape, morphology, and composition. We briefly highlight potential mechanisms of toxicity and conclude with describing the need to transition towards data-intensive computational approaches such as machine learning to establish nMOFs as credible materials for their envisioned applications.