Besides the wide use of engineered nanomaterials (NMs) in technical products, their applications are not only increasing in biotechnology and biomedicine, but also in the environmental field. While the physico-chemical properties and behaviour of NMs can be characterized accurately under idealized conditions, this is no longer the case in complex physiological or natural environments. Herein, proteins and other biomolecules rapidly bind to NMs, forming a protein/biomolecule corona that critically affects the NMs' (patho)biological and technical identities. As the corona impacts the in vitro and/or in vivo NM applications in humans and ecosystems, a mechanistic understanding of its relevance and of the biophysical forces regulating corona formation is mandatory. Based on recent insights, we here critically review and present an updated concept of corona formation and evolution. We comment on how corona signatures may be linked to effects at the nano–bio interface in physiological and environmental systems. In order to comprehensively analyse corona profiles and to mechanistically understand the coronas' biological/ecological impact, we present a tiered multidisciplinary approach. To stimulate progress in this field, we introduce the potential impact of the corona for NM–microbiome–(human)host interactions and the novel concept of ‘nanologicals’, i.e., the nanomaterial-specific targeting of molecular machines. We conclude by discussing the relevant challenges that still need to be resolved in this field.

In this study, the influence of different head groups, functionalised side chains and anions of ionic liquids on the marine bacteria Vibrio fischeri, the limnic green algae Scenedesmus vacuolatus and the fresh water plant Lemna minor was investigated. The aim of these experiments is to improve the knowledge base for the molecular design of ionic liquids leading to a reduced (eco)toxicological hazard potential. The analysed set of about 40 ionic liquids confirmed the interdependency between lipophilicity—as derived from gradient HPLC—and (eco)toxicity. The toxicity was clearly reduced for the test organisms (partially by six to seven orders of magnitude) when short functionalised side chains were used instead of non-polar alkyl chains. Furthermore, we could demonstrate strong interactions of hydrophobic ionic liquid cations with two different types of common biological lipid bilayers, indicating that the membrane system of organisms is probably a primary target site of toxic action. These systematic studies are addressed to producers, developers and downstream users of ionic liquids in different fields of application, to facilitate the selection of (eco)toxicologically favourable structural elements and thus to contribute to the design of inherently safer ionic liquids.

Most recent investigations concerning the toxicological and ecotoxicological risk potentials of ionic liquids are predominantly focusing on the cation moieties. In this study we elucidate, whether the anion species commonly used in ionic liquids are exhibiting intrinsic cytotoxic effects and if these effects can be rationalised by thinking in terms of structure–activity relationships (T-SAR). As test system to measure the cell viability as toxicologically relevant endpoint the IPC-81 rat leukemia cell line and the WST-1 assay were employed. Our results show an anion effect in ionic liquids on cytotoxicity for 10 of 27 tested anions. For the remaining 17 anions from our test kit no significant effect was found. With respect to structure–activity relationships, lipophilicity and/or vulnerability to hydrolytic cleavage seem to be the key structural features leading to the observed anion cytotoxicity. We also conclude that the model of concentration addition may be useful to estimate the EC₅₀ values of ionic liquids that have not been tested or even synthesised yet. This can help to design not only task specific but also inherently safer ionic liquids.

To enlarge the restricted knowledge about the hazard potentials of ionic liquids to man and the environment we have concentrated on analysing systematically the anion effect of six different anion moieties (Cl^– , BF₄ ^– , (CF₃SO₂)₂N^– , (CF₃)₂N^– , octylsulfate and bis(1,2-benzenediolato)borate) and the influence of the side chain length at the cation on (eco)toxicity. For our investigations, we used the flexible (eco)toxicological test battery considering aquatical and terrestrial compartments as well as different trophic levels including enzymes (acetylcholinesterase), mammalian cells (IPC-81), luminescent marine bacteria (Vibrio fischeri), limnic unicellular green algae (Scenedesmus vacuolatus), wheat (Triticum aestivum), cress (Lepidium sativum), duckweed (Lemna minor) and a soil invertebrate (the spring tail Folsomia candida). In general, the side chain effect was found consistently in all used test systems from the molecular up to the organismic level. Such a consistent response of the different test systems could not be confirmed for the tested anion moieties. Furthermore, in most of the investigated test systems the anion effects are not as distinct as the demonstrated side chain length effect. Nevertheless, for (CF₃SO₂)₂N^– a clear (eco)toxicological hazard potential is evident. Thus, the strategy to check toxicities within a flexible (eco)toxicological test battery has been proven to be effective for uncovering hazard potentials of ionic liquids.