A combined targeted/untargeted LC-MS/MS-based screening approach for mammalian cell lines treated with ionic liquids: Toxicity correlates with metabolic profile.

This work presents the development and validation of a quantitative HILIC UHPLC-ESI-QTOF-MS/MS method for amino acids combined with untargeted metabolic profiling of human corneal epithelial (HCE) cells after treatment with ionic liquids. The work included a preliminary metabotoxicity screening of 14 different ionic liquids, of which 9 carefully selected ionic liquids were chosen for a metabolomics study. This study is focused on the correlation between the toxicity of the ionic liquids and their metabolic profiles. The method development included the comparison of different MS/MS acquisition modes. A sequential window acquisition of all theoretical fragment ion mass spectra (SWATH) method with variable Q1 window widths and narrow Q1 target windows of 5 Da for most of the amino acids was selected as the optimal acquisition mode. Due to the absence of a true blank matrix, 13C,15N-isotopically labelled amino acids were utilized as surrogate calibrants, instead of proteinogenic amino acids. Partial least squares (PLS) analysis of the median effective concentrations (EC50) of 9 selected ionic liquids showed a correlation with their metabolic profile measured by the untargeted screening.

Comparison of simple monophasic versus classical biphasic extraction protocols for comprehensive UHPLC-MS/MS lipidomic analysis of Hela cells.

In this study, two monophasic isopropanol-water mixtures (IPA:H2O 75:25 v/v and IPA:H2O 90:10 v/v) were compared with traditionally employed biphasic methods of Bligh & Dyer and Matyash et al. as extraction systems for lipidomics analysis in Hela cells. Samples were analyzed by UHPLC-ESI-QTOF-MS/MS in positive and negative mode using sequential window acquisition of all theoretical fragment ion spectra (SWATH) and a relatively new software (MS-DIAL) was employed for the processing of the data which includes detection of peaks, MS/MS spectra deconvolution, identification of detected lipids and alignment of peaks through the analyzed samples. The studied performance parameters such as precision, recoveries of isotopically labeled internal standards and endogenous lipids, number of extracted lipids, and complexity of employed procedure showed that extraction with IPA:H2O 90:10 v/v performs similar to the Matyash protocol and better than Bligh & Dyer as well as IPA:H2O 75:25 v/v. However, less complex monophasic protocol which is simpler to implement and can be executed in plastic rather than glass, make the monophasic IPA:H2O 90:10 v/v protocol an excellent alternative to the classical biphasic protocols for reversed phase LC-MS lipidomics studies.

Correlation between Ionic Liquid Cytotoxicity and Liposome-Ionic Liquid Interactions.

This study aims at extending the understanding of the toxicity mechanism of ionic liquids (ILs) using various analytical methods and cytotoxicity assays. The cytotoxicity of eight ILs and one zwitterionic compound was determined using mammalian and bacterial cells. The time dependency of the IL toxicity was assessed using human corneal epithelial cells. Hemolysis was performed using human red blood cells and the results were compared with destabilization data of synthetic liposomes upon addition of ILs. The effect of the ILs on the size and zeta potential of liposomes revealed information on changes in the lipid bilayer. Differential scanning calorimetry was used to study the penetration of the ILs into the lipid bilayer. Pulsed field gradient nuclear magnetic resonance spectroscopy was used to determine whether the ILs occurred as unimers, micelles, or if they were bound to liposomes. The results show that the investigated ILs can be divided into three groups based on the cytotoxicity mechanism: cell wall disrupting ILs, ILs exerting toxicity through both cell wall penetration and metabolic alteration, and ILs affecting solely on cell metabolism.

Effect of Ionic Liquids on Zebrafish (Danio rerio) Viability, Behavior, and Histology; Correlation between Toxicity and Ionic Liquid Aggregation.

The effect of 11 common amidinium, imidazolium, and phosphonium based ionic liquids (ILs) on zebrafish (Danio rerio) and Chinese hamster ovary cells (CHO) was investigated with specific emphasis on the effect of anion and cation chain length and aggregation of phosphonium based ILs. Viability and behavioral alteration in the locomotor activity and place preference, after IL treatment of 5 days postfertilization larvae, was recorded. Behavior and histological damage evaluation was performed for adult fish in order to get insight into the long-term effects of two potential biomass-dissolving ILs, [DBNH][OAc] and [P4441][OAc]. To get an understanding of how IL aggregation is linked to the toxicity of ILs, median effective concentrations (EC50) and critical micelle concentrations (CMC) were determined. The long-chain ILs were significantly more toxic than the short-chain ones, and the anion chain length was shown to be less significant than the cation chain length when assessing the impact of ILs on the viability of the organisms. Furthermore, most of the ILs were as monomers when the EC50 was reached. In addition, the ILs used in the long-term tests showed no significant effect on the zebrafish behavior, breeding, or histology, within the used concentration range.

Surface-crosslinked poly(3-mercaptopropyl)methylsiloxane-coatings on silica as new platform for low-bleed mass spectrometry-compatible functionalized stationary phases synthesized via thiol-ene click reaction.

A thin functional film of poly(3-mercaptopropyl)methylsiloxane was coated onto vinyl-modified silica particles (5µm, 100Å pore size) and chemically crosslinked to the surface. Excess of thiol functionalities allow bonding of alkene containing ligands by thiol-ene click reaction in a second step (QN-VII). Besides that a single step surface modification procedure was established in which alkene functional ligands were directly added to the polysiloxane coating solution and thus, after evaporation of the solvent, crosslinking to the vinylized surface and bonding of chromatographic ligand to the thiolated polysiloxane film occur simultaneously in one step (QN-VI). Successful bonding of the polysiloxane film was confirmed for both approaches by (29)Si cross-polarization/magic angle spinning NMR spectra. The new surface functionalization concept can be utilized as a new platform for the preparation of various low-bleed, mass spectrometry-compatible stationary phases with a variety of functional ligands. The concept was demonstrated by thiol-ene click reaction with quinine carbamate and its subsequent use for enantiomer separation by HPLC-UV and HPLC-ESI-QTOF-MS of acidic chiral analytes. Chromatographic enantioselectivities were similar to a comparable brush-type CSP (QN-V0). The greatly reduced background signal in LC-MS, however, comes at expense of somewhat lower chromatographic efficiencies (C-term by factor of 2 larger compared to brush-type CSP). For quantitative analysis in single reaction monitoring (MRM(HR)) in high sensitivity mode, limit of detection and limit of quantification results are comparable for both surface-polymer modified CSPs, with only slightly higher values for the conventional brush-type CSP (QN-V0).