Micro-( 5 mm) and nanoplastics ( 1 μm) are emerging threats for marine ecosystems worldwide. Brine shrimp Artemia is recognized as a suitable model among planktonic species for studying the impact of polystyrene nanoparticles (PS NPs) through short and long-term bioassays. Our study aims to evaluate the timedependent effects of cationic amino-modified PS-NH 2 (50 nm) in A. franciscana after short-(48 h) and long-term exposure (14 days). For this purpose, nauplii were exposed to a concentration range of PS-NH 2 (0.1, 1, 3 and 10 µg/mL) in natural sea water (NSW), and physiological, biochemical and molecular responses were investigated. Short-term exposure to PS-NH 2 caused a decrease in nauplii growth and affected the development in a concentration-dependent manner, long-term exposure impaired the survival, but not the growth and feeding behavior. Oxidative stress was detected after short term exposure as the decrease in the activity of antioxidant enzymes, and was fully evident in the long-term as lipid peroxidation, suggesting an accumulative effect. The decrease in Cholinesterase (ChE) activity observed indicates possible neurotoxic action of PS-NH 2. Also, Carboxylesterase (CbE) inhibition by PS-NH 2, described for the first time in this study, anticipates potential effects in biotransformation of exogenous and endogenous compounds, being the crustacean juvenile hormone methyl farnesoate (MF) that regulates development and molting, one candidate. Furthermore, short-and long-term exposure to PS-NH 2 affect the expression of genes involved in cell protection, development and molting. Overall, our results reveal that low PS-NH 2 concentrations induce physiological, biochemical and molecular (changes in gene expression) alterations in Artemia, and point at their potential risk for this model organism, supporting the general concern about nanoplastics occurrences in aquatic environments and their ability to represent an ecological threat for aquatic zooplanktonic species.

Graphical abstract

The outer membrane of Gram-negative bacteria contains β-barrel proteins that form high-conducting ion channels providing a path for hydrophilic molecules, including antibiotics. Traditionally, these proteins have been considered to exist only in an open state so that regulation of outer membrane permeability was accomplished via protein expression. However, electrophysiological recordings show that β-barrel channels respond to transmembrane voltages by characteristically switching from a high-conducting, open state, to a so-called ‘closed’ state, with reduced permeability and possibly exclusion of large metabolites. Here, we use the bacterial porin OmpF from E. coli as a model system to gain insight on the control of outer membrane permeability by bacterial porins through the modulation of their open state. Using planar bilayer electrophysiology, we perform an extensive study of the role of membrane lipids in the OmpF channel closure by voltage. We pay attention not only to the effects of charges in the hydrophilic lipid heads but also to the contribution of the hydrophobic tails in the lipid-protein interactions. Our results show that gating kinetics is governed by lipid characteristics so that each stage of a sequential closure is different from the previous one, probably because of intra- or intermonomeric rearrangements.

We show that the interaction of trivalent electrolytes with biological nanopores occurs via ion-specific adsorption yielding differential modulation of ion conduction and selectivity inversion.