Abstract
Bioaccumulation potential is critical in PBT and risk assessment of chemicals. However, for ionic liquids (ILs), this aspect remains neglected. It is especially important to fill this gap, because for this group of compounds, existing data confirm their risk of being environmentally persistent and toxicity. Moreover, considering preliminary reports on the interactions of ILs with lipids, it may be assumed that ILs have a higher potential for bioaccumulation than indicated by previous estimations built upon octanol–water partition coefficients. Moreover, the bioconcentration of ionizable chemical compounds may also be strongly related to plasma protein contents. Therefore, in this work, the affinity of a set of imidazolium cations and organic anions, and their combination to human serum albumin (HSA) was determined. The obtained results reveal that both cations and anions can be strongly bound to HSA, and blood proteins might play an important role in overall bioaccumulation. Furthermore, it was observed that HSA binding properties towards IL cations depend on the hydrophobicity of cations. The obtained data also provide indication that cation–anion interaction may affect ILs ions affinity to HSA.
Highlights
The accumulation of chemicals in biota is of major concern for environmental hazard and risk assessment
Determining the equilibrium time of ionic liquids (ILs) partitioning to protein, non-specific binding (NSB) and critical micelle concentration (CMC)
It is worth noticing that the binding constants of the [C(8) mim][B(CN)4]/(HSA) and K[B(CN)4]/(HSA) complexes are equal in the range of the experimental error. This suggests that the affinity of the IL anions towards human serum albumin (HSA) is higher than the IL cations comprising alkyl chain lengths lower than 12. These results show the utmost importance of focus‐ sing on both the cation and anion of ILs separately when the assessment of the interaction with bio‐ molecules, e.g. proteins, in an aqueous solution is conducted by methods like ITC or by other techniques that are not based on the quantitation of the free fraction of the cation and/or anion in the water phase, but on the other effects of protein binding
Summary
The accumulation of chemicals in biota is of major concern for environmental hazard and risk assessment. For this rea‐ son, bioaccumulation assessment is a part of international efforts to identify and control chemicals of environmen‐ tal concern. Membrane and storage lipids have been con‐ sidered as underlying compartments in the bioaccumula‐ tion of organic chemicals (Geisler et al 2012; Endo et al 2011). In the assessment of bioaccumulation potential by using octanol–water partition coefficients (LogKOW), the assumption held is that the bioaccumulation of substances is determined mainly by the partitioning between lipid and aqueous phases (Mackay et al 1982, Meylan et al 1996). The bioconcentration/bioaccumulation poten‐ tial of chemicals is defined by lipid partitioning. Knowledge regarding the partitioning of these compounds to
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