Ionic liquids in enhancing the sensitivity of capillary electrophoresis: Off-line and on-line sample preconcentration techniques

Ionic liquids in capillary electrophoresis analysis of proteins and carbohydrates

Ionic liquids (ILs), as non-molecular type solvents, possess excellent physical-chemical properties, which make them useful in important separation applications in gas chromatography, liquid chromatography, and capillary electrophoresis. Among a plethora of potential uses of ionic liquids in separation science, capillary electrophoresis can utilize its resolution-enhancing effect in the analysis of proteins and carbohydrates, via the formation of intermolecular interactions, e.g., hydrophobic, hydrogen bonding, or electrostatic. ILs and polymeric ionic liquids (PIL) also represent an excellent choice as background electrolyte (BGE) additives for capillary coatings in CE, which is especially important in protein analysis. Another interesting utilization of ILs is the fabrication of monoliths for capillary electrochromatography in which instance the mechanism of retention is based on ion exclusion interactions. Carbohydrates can also be readily analyzed by CE with the help of ionic liquids without the need for an extra derivatization step. One of the future perspectives on the use of ILs is their utilization in the recently emerging biopharmaceutical industry exploiting the increased resolution of proteins and carbohydrates, two of the important components of glycoprotein therapeutics. In this paper, we address the so-far not-reviewed ionic liquid-mediated analysis of proteins and carbohydrates by capillary electrophoresis-based techniques also addressing their impact on the separation mechanism.

Ionic liquids revolutionizing biomedicine: recent advances and emerging opportunities

Ionic liquids (ILs), due to their inherent structural tunability, outstanding miscibility behavior, and excellent electrochemical properties, have attracted significant research attention in the biomedical field. As the application of ILs in biomedicine is a rapidly emerging field, there is still a need for systematic analyses and summaries to further advance their development. This review presents a comprehensive survey on the utilization of ILs in the biomedical field. It specifically emphasizes the diverse structures and properties of ILs with their relevance in various biomedical applications. Subsequently, we summarize the mechanisms of ILs as potential drug candidates, exploring their effects on various organisms ranging from cell membranes to organelles, proteins, and nucleic acids. Furthermore, the application of ILs as extractants and catalysts in pharmaceutical engineering is introduced. In addition, we thoroughly review and analyze the applications of ILs in disease diagnosis and delivery systems. By offering an extensive analysis of recent research, our objective is to inspire new ideas and pathways for the design of innovative biomedical technologies based on ILs.

Synthesis of Purine-Based Ionic Liquids and Their Applications

Bio-based ionic liquids (ILs) are being increasingly sought after, as they are more sustainable and eco-friendly. Purines are the most widely distributed, naturally occurring N-heterocycles, but their low water-solubility limits their application. In this work, four purines (theobromine, theophylline, xanthine, and uric acid) were combined with the cation tetrabutylammonium to synthesize bio-based ILs. The physico-chemical properties of the purine-based ILs were characterized, including their melting and decomposition temperatures and water-solubility. The ecotoxicity against the microalgae Raphidocelis subcapitata was also determined. The ILs show good thermal stability (>457 K) and an aqueous solubility enhancement ranging from 53- to 870-fold, in comparison to their respective purine percursors, unlocking new prospects for their application where aqueous solutions are demanded. The ecotoxicity of these ILs seems to be dominated by the cation, and it is similar to chloride-based IL, emphasizing that the use of natural anions does not necessarily translate to more benign ILs. The application of the novel ILs in the formation of aqueous biphasic systems (ABS), and as solubility enhancers, was also evaluated. The ILs were able to form ABS with sodium sulfate and tripotassium citrate salts. The development of thermoresponsive ABS, using sodium sulfate as a salting-out agent, was accomplished, with the ILs having different thermosensitivities. In addition, the purine-based ILs acted as solubility enhancers of ferulic acid in aqueous solution.

[Advances in chromatography in the study of drug-plasma protein interactions]

小分子药物进入人体血液循环系统后与人血清白蛋白(HSA)、α₁ -酸性糖蛋白(AGP)等血浆蛋白存在广泛的相互作用,这些相互作用深刻影响药物在体内的分布及其与靶标蛋白的结合,进而影响药物效应的发挥。深入探究药物与血浆蛋白间的相互作用对于候选药物的成药性优化、新药研发、联合用药的风险评控等意义重大。而发展高效、灵敏、准确的分析检测方法是开展药物-血浆蛋白相互作用研究的关键。近年来,色谱技术由于其高通量、高分离性能、高灵敏度等特点在该领域得到了广泛的应用,包括测定血浆蛋白翻译后修饰对药物结合的影响,多种药物的竞争性结合等。其中,高效亲和色谱(HPAC)和毛细管电泳(CE)应用最为广泛,能够通过多种分析方法获取结合常数、结合位点数、解离速率常数等相互作用信息。该文着重综述了HPAC和CE在药物-血浆蛋白相互作用研究中的常用策略及最新研究进展,包括HPAC中常用的前沿色谱法、竞争洗脱法、超快亲和提取法、峰值分析法和峰衰减分析法,以及CE中常用的亲和毛细管电泳法(ACE)和毛细管电泳前沿分析法(CE-FA)等。最后,该文还对当前色谱方法存在的不足进行了总结,并对色谱技术在药物-血浆蛋白相互作用研究领域的应用前景和发展方向进行了展望。

Ionic liquids in electrokinetic chromatography

There is an interest in the application of ionic liquids as additives into the separation media to improve achiral and chiral separations in electrokinetic chromatography (EKC). This review will critically discuss the developments on the use of ionic liquids in the different modes of EKC during the last five years (2015-mid 2020). A healthy number of 48 research articles searched through Scopus were categorised into two: ionic liquids as sole pseudophase (micelles, microemulsions, ligand exchange pseudophase or molecular pseudophase) and ionic liquids with pseudophase (achiral or chiral). More than half of the papers dealt with chiral separations that were mostly facilitated by another additive or pseudophase. The role of ionic liquids for improvement of separations were analysed, and we provided some recommendations for further investigations. Finally, the use of ionic liquids in different on-line sample concentration or stacking methods (i.e., field enhancement and sweeping) was briefly discussed.

Ionic Liquid Aqueous Two-Phase Systems From a Pharmaceutical Perspective

Aqueous Two-Phase Systems (ATPSs) have been extensively studied for their ability to simultaneously separate and purify active pharmaceutical ingredients (APIs) and key intermediates with high yields and high purity. Depending on the ATPS composition, it can be adapted for the separation and purification of cells, nucleic acids, proteins, antibodies, and small molecules. This method has been shown to be scalable, allowing it to be used in the milliliter scale for early drug development to thousands of liters in manufacture for commercial supply. The benefits of ATPS in pharmaceutical separations is increasingly being recognized and investigated by larger pharmaceutical companies. ATPSs use identical instrumentation and similar methodology, therefore a change from traditional methods has a theoretical low barrier of adoption. The cost of typical components used to form an ATPS at large scale, particularly that of polymer-polymer systems, is the primary challenge to widespread use across industry. However, there are a few polymer-salt examples where the increase in yield at commercial scale justifies the cost of using ATPSs for macromolecule purification. More recently, Ionic Liquids (ILs) have been used for ATPS separations that is more sustainable as a solvent, and more economical than polymers often used in ATPSs for small molecule applications. Such IL-ATPSs still retain much of the attractive characteristics such as customizable chemical and physical properties, stability, safety, and most importantly, can provide higher yield separations of organic compounds, and efficient solvent recycling to lower financial and environmental costs of large scale manufacturing.

Ionic liquid-based headspace in-tube liquid-phase microextraction coupled with capillary electrophoresis for sensitive detection of phenols

An ionic liquid-based headspace in-tube liquid-phase microextraction (IL-HS-ITLPME) in-line coupled with capillary electrophoresis (CE) is proposed. The method is capable of quantifying trace amounts of phenols in environmental water samples. In the newly developed method, simply by placing a capillary injected with IL in the HS above the aqueous sample, volatile phenols were extracted into the IL acceptor phase in the capillary. After extraction, electrophoresis of the phenols in the capillary was carried out. Extraction parameters such as the extraction time, extraction temperature, ionic strength, volume of the sample solution and IL types were systematically investigated. Under the optimized conditions, enrichment factors for four phenols were from 1510 to 1985. The proposed method provided a good linearity, low limits of detection (below 5.0 ng mL-1 ), and good repeatability of the extractions (RSDs below 6.7%, n = 6). This method was then utilized to analyze two real environmental samples of Xiaoxi Lake and tap water, obtaining acceptable recoveries and precisions. Compared with the usual HS-ITLPME for CE, IL-HS-ITLPME-CE is a simple, low-cost, fast and environmentally friendly pre-concentration technique. This article is protected by copyright. All rights reserved.