Quaternary Ammonium Compounds (QACs) and Ionic Liquids (ILs) as Biocides: From Simple Antiseptics to Tunable Antimicrobials.

Quaternary ammonium compounds (QACs) belong to a well-known class of cationic biocides with a broad spectrum of antimicrobial activity. They are used as essential components in surfactants, personal hygiene products, cosmetics, softeners, dyes, biological dyes, antiseptics, and disinfectants. Simple but varied in their structure, QACs are divided into several subclasses: Mono-, bis-, multi-, and poly-derivatives. Since the beginning of the 20th century, a significant amount of work has been dedicated to the advancement of this class of biocides. Thus, more than 700 articles on QACs were published only in 2020, according to the modern literature. The structural variability and diverse biological activity of ionic liquids (ILs) make them highly prospective for developing new types of biocides. QACs and ILs bear a common key element in the molecular structure-quaternary positively charged nitrogen atoms within a cyclic or acyclic structural framework. The state-of-the-art research level and paramount demand in modern society recall the rapid development of a new generation of tunable antimicrobials. This review focuses on the main QACs exhibiting antimicrobial and antifungal properties, commercial products based on QACs, and the latest discoveries in QACs and ILs connected with biocide development.

"Solvent-in-salt" systems for design of new materials in chemistry, biology and energy research.

Inorganic and organic "solvent-in-salt" (SIS) systems have been known for decades but have attracted significant attention only recently. Molten salt hydrates/solvates have been successfully employed as non-flammable, benign electrolytes in rechargeable lithium-ion batteries leading to a revolution in battery development and design. SIS with organic components (for example, ionic liquids containing small amounts of water) demonstrate remarkable thermal stability and tunability, and present a class of admittedly safer electrolytes, in comparison with traditional organic solvents. Water molecules tend to form nano- and microstructures (droplets and channel networks) in ionic media impacting their heterogeneity. Such microscale domains can be employed as microreactors for chemical and enzymatic synthesis. In this review, we address known SIS systems and discuss their composition, structure, properties and dynamics. Special attention is paid to the current and potential applications of inorganic and organic SIS systems in energy research, chemistry and biochemistry. A separate section of this review is dedicated to experimental methods of SIS investigation, which is crucial for the development of this field.

Cytotoxic Activity of Salicylic Acid-Containing Drug Models with Ionic and Covalent Binding.

Three different types of drug delivery platforms based on imidazolium ionic liquids (ILs) were synthesized in high preparative yields, namely, the models involving (i) ionic binding of drug and IL; (ii) covalent binding of drug and IL; and (iii) dual binding using both ionic and covalent approaches. Seven ionic liquids containing salicylic acid (SA-ILs) in the cation or/and in the anion were prepared, and their cytotoxicity toward the human cell lines CaCo-2 (colorectal adenocarcinoma) and 3215 LS (normal fibroblasts) was evaluated. Cytotoxicity of SA-ILs was significantly higher than that of conventional imidazolium-based ILs and was comparable to the pure salicylic acid. It is important to note that the obtained SA-ILs dissolved in water more readily than salicylic acid, suggesting benefits of possible usage of traditional nonsoluble active pharmaceutical ingredients in an ionic liquid form.

Efficient Sustainable Tool for Monitoring Chemical Reactions and Structure Determination in Ionic Liquids by ESI-MS.

An easy and convenient procedure is described for monitoring chemical reactions and characterization of compounds dissolved in ionic liquids using the well-known tandem mass spectrometry (MS/MS) technique. Generation of wastes was avoided by utilizing an easy procedure for analysis of ionic liquid systems without preliminary isolation and purification. The described procedure also decreased the risk of plausible contamination and damage of the ESI-MS hardware and increased sensitivity and accuracy of the measurements. ESI-MS detection in MS/MS mode was shown to be efficient in ionic liquids systems for structural and mechanistic studies, which are rather difficult otherwise. The developed ESI-MS/MS approach was applied to study samples corresponding to peptide systems in ionic liquids and to platform chemical directed biomass conversion in ionic liquids.