Abstract
The skin is the part of the body that is the most exposed to toxic substances; therefore, the impact of chemicals on the skin should be thoroughly studied prior to their implementation in any industrial-scale application. Herein, we examined and analyzed the influence of the structure of both the cation and anion of 31 different ionic liquids (ILs) on their cytotoxicity against normal human dermal fibroblasts in the context of their present and future potential applications. We found that imidazolium-based ILs combined with dialkyl phosphate anions or with the ethyl sulfate anion are the least cytotoxic. Notably, 1,3-diethylimidazolium ethyl sulfate can be potentially used as a hydraulic fluid similar to the commercially available hydraulic medium based on 1-ethyl-3-methylimidazolium ethyl sulfate. Moreover, the dialkyl phosphate-based ILs are considered as an efficient solvent for the utilization of lignocellulose-based biomass and as an extractant in eco-friendly and cost-effective processes for the extraction of bioplastic. Pyrrolidinium-based and cyano-based ILs, often used as heat transfer media and base fluids for ionanofluids, were also identified herein as good candidates based on their relatively low toxicity compared to other ILs.
Highlights
Ionic liquids (ILs) have achieved great success due to their unique features such as high chemical and thermal stability and low vapor pressure, and because they are non-explosive, nonflammable, and much more. This has resulted in a huge number of applications on an industrial scale, e.g., biphasic acid scavenging utilizing ionic liquids (BASIL) and cellulose dissolution BASF company; hydraulic ionic liquid compressor Linde Group; TEGO1 Dispers and hydrosilylation process Degussa company; batteries Pionics, NantEnergy, NOHMs Technologies; and isomerization process Eastman Chemical Company.[1,2]
The normal human dermal fibroblasts (NHDF) cell line was employed to investigate the cytotoxicity of ILs because it is a common and reliable model for measuring the toxicity in in vitro initial studies
Many studies have analyzed the toxicity of ILs on human cell lines.[16,29−33] there are few existing studies on the influence of the anion structure in ILs on the cytotoxicity in contrast to the numerous studies that have investigated the impact of the alkyl chain length in the cation
Summary
Ionic liquids (ILs) have achieved great success due to their unique features such as high chemical and thermal stability and low vapor pressure, and because they are non-explosive, nonflammable, and much more. This has resulted in a huge number of applications on an industrial scale, e.g., biphasic acid scavenging utilizing ionic liquids (BASIL) and cellulose dissolution BASF company; hydraulic ionic liquid compressor Linde Group (world-leading gases and engineering company); TEGO1 Dispers (paint additives) and hydrosilylation process Degussa company; batteries Pionics, NantEnergy, NOHMs Technologies; and isomerization process Eastman Chemical Company.[1,2] Because of the extensive use of ILs in academic research and the chemical industry, and due to their high stability and noticeable solubility (especially in water), their environmental impact cannot be avoided. Ionic liquids used to be called “green solvents′′3 due to their negligible vapor pressure They are usually less volatile than most classic organic solvents and do not pollute the air. ILs may be potential water and soil pollutants, especially during operational discharges or accidental leaks, and their general toxicity plays a crucial role.[4−6] While many ILs have proven to be toxic, and in some cases, more toxic than common organic solvents, there has still not been enough attention paid to the effects of ILs on humans and the environment.[7−9]
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