A review on (eco)toxicity of ionic liquids and their interaction with phospholipid membranes

Ionic liquids (ILs) are salt-like organic compounds that are composed of organic cations and organic/inorganic anions. The constituting ions play a crucial role in dictating their physicochemical properties and biological activities. ILs since their discovery have been explored for a variety of applications and they prove to be an excellent category of molecules which can be used in almost all sectors of research and applications. However, from the last few decades, the toxicity of ILs has also become a hot topic as they have been found to induce harmful impacts on all forms of life including marine life and the life on earth. There has been an ongoing effort to understand how the ILs and the structural features of ions induce toxicity and which structural parameters should be introduced or changed in order to design environment benign and greener ILs. The interaction of ILs with cell membranes is the most accepted mechanism which leads to the toxic character of the ILs. This review comprises the journey of ILs from their discovery to the times when they were considered a boon and now when their toxic impacts are well known. An overview of the studies is provided which have been carried on to study the toxic behavior of ILs towards a variety of living beings including all variety of plants, living organisms, and cell lines. The structural features of ions are discussed which impact these adverse impacts shown by the ILs. Moreover, this review focuses on the discussion of various techniques and studies which have been used to study and understand the interaction of ILs with lipid membranes. The studies have shown that the toxicity of ILs can be estimated from the interaction of ILs with membranes. ILs turn out to be more toxic when the hydrophobicity of the ions is increased. This review will be helpful to the readers to get a better insight into the toxicity and ILs-membrane interactions along with a scope to understand how the structural features of ions can be varied to design greener ILs.