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Special Issue "Ionic Liquids for Chemical and Biochemical Applications II"

A special issue of Molecules (ISSN 1420-3049).

Deadline for manuscript submissions: 31 December 2020.

Special Issue Editors

Prof. Dr. Po-Yu Chen
Website
Guest Editor
Department of Medicinal and Applied Chemistry, Kaohsiung Medical University, Kaohsiung 807, Taiwan
Interests: ionic liquid electrolyte; electrodeposition; electrocatalysis; electroanalysis; modified electrode; electrochemical fabrication of nanostructures
Prof. Dr. Jing-Fang Huang
Website
Guest Editor
Department of Chemistry, National Chung Hsing University, Taichung 402, Taiwan
Interests: alloying–dealloying technique; nanoporous structure; electrochemical detection; proton conductor; nanoparticle; electrocatalyst; electrocatalytic reaction; task-specific ionic liquid
Prof. Dr. Yen-Ho Chu
Website
Guest Editor
Department of Chemistry and Biochemistry, National Chung Cheng University, 168 University Road, Minhsiung, Chiayi 62102, Taiwan
Interests: newfangled ionic liquid; combinatorial organic synthesis; affinity ionic liquid; biomolecular recognition; functionalized ionic liquid; chemoselective gas analysis; bioorganic and bioanalytical chemistry
Special Issues and Collections in MDPI journals

Special Issue Information

Dear colleagues,

Ionic liquids are ionic, nonvolatile alternatives to conventional volatile molecular solvents and have recently received impressive attention in many aspects of chemical, electrochemical, and biochemical applications.

This year, the journal Molecules is to publish the second edition of a Special Issue with a collection of papers featuring selected contributions from Ionic Liquids for Chemical and Biochemical Applications II. As guest editors of this Special Issue, we are writing to invite you to contribute a research paper, rapid communication, or review article on your latest research activities in ionic liquids.

This Special Issue will be a collection of papers focusing on ionic liquids as smart materials for electrocatalytic as well as electrochemical analysis, and ionic liquid devices for affinity extraction and analysis. We anticipate that this issue will be attractive to the scientific community of synthesis, materials, and separation, and we invite contributions covering the aspects broadly indicated by the keywords. Reviews articles by experts are also welcomed.

Prof. Dr. Po-Yu Chen
Prof. Dr. Jing-Fang Huang
Prof. Dr. Yen-Ho Chu
Guest Editors

Manuscript Submission Information

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All papers will be peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Molecules is an international peer-reviewed open access semimonthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2000 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

  • Ionic liquid
  • Ionic liquid electrolyte
  • Electroanalysis
  • Electrocatalysis
  • Electrodeposition
  • Electrochemical fabrication of nanostructures
  • Protic ionic liquid
  • Materials in ionic liquid
  • Ionic solvent
  • Organic reaction
  • Natural product in ionic liquid
  • Gas sensing
  • Affinity extraction
  • Chromatographic separation
  • Zwitterionic liquid
  • Functional ionic liquid
  • Bioactivity
  • Enzymatic catalysis
  • DNA, protein, peptide, and carbohydrate
  • Desalination and water treatment
  • Polymer dissolution
  • Oil extraction
  • Task-specific ionic liquid

Published Papers (6 papers)

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Research

Open AccessArticle
Coupling of Bioreaction and Separation via Novel Thermosensitive Ionic Liquids Applied in the Baker’s Yeast-Catalyzed Reduction of Ethyl 2-oxo-4-phenylbutyrate
Molecules 2020, 25(9), 2056; https://doi.org/10.3390/molecules25092056 - 28 Apr 2020
Abstract
The use of baker’s yeast to reduce ethyl 2-oxo-4-phenylbutyrate (EOPB) in conventional biphasic systems is hindered by low productivities due to mass transfer resistance between the biocatalyst and the substrate partitioned into two different phases. To overcome the limitation, a new reaction-separation coupling [...] Read more.
The use of baker’s yeast to reduce ethyl 2-oxo-4-phenylbutyrate (EOPB) in conventional biphasic systems is hindered by low productivities due to mass transfer resistance between the biocatalyst and the substrate partitioned into two different phases. To overcome the limitation, a new reaction-separation coupling process (RSCP) was configured in this study, based on the novel thermosensitive ionic liquids (ILs) with polyoxyethylene-tail. The solubility of ILs in common solvents was investigated to configure the unique thermosensitive ionic liquids–solvent biphasic system (TIBS) in which the reduction was performed. [(CH3)2N(C2H5)(CH2CH2O)2H][PF6] (c2) in 1,2-dimethoxyethane possesses the thermosensitive function of homogeneous at lower temperatures and phase separating at higher temperatures. The phase transformation temperature (PTT) of the mixed system of c2/1,2-dimethoxyethane (v/v, 5:18) was about 33 °C. The bioreaction takes place in a “homogeneous” liquid phase at 30 °C. At the end of each reduction run, the system temperature is increased upon to the PTT, while c2 is separated from 1,2-dimethoxyethane with turning the system into two phases. The enantiomeric excesses (e.e.) of ethyl (R)-2-hydroxy-4-phenylbutyrate ((R)-EHPB) increased about 25~30% and the yield of ethyl-2-hydroxy-4-phenylbutyrate (EHPB) increased 35% in TIBS, compared with the reduction in 1,2-dimethoxyethane. It is expected that the TIBS established in this study could provide many future opportunities in the biocatalysis. Full article
(This article belongs to the Special Issue Ionic Liquids for Chemical and Biochemical Applications II)
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Open AccessArticle
New Strategy to Preserve Phosphate by Ionic Liquid Matrices in Matrix-Assisted Laser Desorption/Ionization: A Case of Adenosine Nucleotides
Molecules 2020, 25(5), 1217; https://doi.org/10.3390/molecules25051217 - 08 Mar 2020
Abstract
Adenosine -5′-triphosphate (ATP) plays a valuable role in metabolic activity to produce adequate energy in a biosystem. A high ATP/AMP ratio has a correlation with diabetes that induces suppression of AMP-activated protein kinase (AMPK). Matrix-assisted laser desorption/ionization (MALDI)–mass spectrometry (MS) has outstanding potential [...] Read more.
Adenosine -5′-triphosphate (ATP) plays a valuable role in metabolic activity to produce adequate energy in a biosystem. A high ATP/AMP ratio has a correlation with diabetes that induces suppression of AMP-activated protein kinase (AMPK). Matrix-assisted laser desorption/ionization (MALDI)–mass spectrometry (MS) has outstanding potential in determining the ratio of several types of adenosine phosphates in a sample to rapidly understand the primary energy transfer in metabolism. Although MALDI is viewed as a soft ionization technique for MS analysis, excess photon energy might crack the phosphate bonds leading to misinterpretation of the ATP level. In this work, ionic liquid matrices (ILMs) were employed to reduce fragmentation and increase the detection efficiency during the MALDI process. This study demonstrated for the first time that 2,5-dihydroxybenzoic acid pyridine (DHBP) is one of the most effective matrices for further quantitative analysis of adenosine nucleotides. This systematic screening of ILMs also enhances the fundamental understanding of MALDI. Full article
(This article belongs to the Special Issue Ionic Liquids for Chemical and Biochemical Applications II)
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Open AccessCommunication
Reaction-Based Amine and Alcohol Gases Detection with Triazine Ionic Liquid Materials
Molecules 2020, 25(1), 104; https://doi.org/10.3390/molecules25010104 - 27 Dec 2019
Abstract
We demonstrated in this work the use of affinity ionic liquids, AIL 1 and AIL 2, for chemoselective detection of amine and alcohol gases on a quartz crystal microbalance (QCM). These detections of gaseous amines and alcohols were achieved by nucleophilic aromatic [...] Read more.
We demonstrated in this work the use of affinity ionic liquids, AIL 1 and AIL 2, for chemoselective detection of amine and alcohol gases on a quartz crystal microbalance (QCM). These detections of gaseous amines and alcohols were achieved by nucleophilic aromatic substitution reactions with the electrophilic 1,3,5-triazine-based AIL 1 thin-coated on quartz chips. Starting with inexpensive reagents, bicyclic imidazolium ionic liquids AIL 1 and AIL 2 were readily synthesized in six and four synthetic steps with high isolated yields: 51% and 63%, respectively. The QCM platform developed in this work is readily applicable and highly sensitive to low molecular weight amine gases: for isobutylamine gas (a bacterial volatile) at 10 Hz decrease in resonance frequency (i.e., ΔF = −10 Hz), the detectability using AIL 1 was 6.3 ppb. Our preliminary investigation on detection of the much less nucleophilic alcohol gas by AIL 1 was also promising. To our knowledge, no example to date of reports based on nucleophilic aromatic substitution reactions demonstrating sensitive gas detection in these triazine ionic liquids on a QCM has been reported. Full article
(This article belongs to the Special Issue Ionic Liquids for Chemical and Biochemical Applications II)
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Open AccessCommunication
AC Electrodeposition of PEDOT Films in Protic Ionic Liquids for Long-Term Stable Organic Electrochemical Transistors
Molecules 2019, 24(22), 4105; https://doi.org/10.3390/molecules24224105 - 14 Nov 2019
Abstract
Poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS)-based organic electrochemical transistors (OECTs) are widely utilized to construct highly sensitive biosensors. However, the PSS phase exhibits insulation, weak acidity, and aqueous instability. In this work, we fabricated PEDOT OECT by alternating current electrodeposition in protic ionic liquids. The steady-state characteristics [...] Read more.
Poly(3,4-ethylenedioxythiophene):poly(4-styrenesulfonate) (PEDOT:PSS)-based organic electrochemical transistors (OECTs) are widely utilized to construct highly sensitive biosensors. However, the PSS phase exhibits insulation, weak acidity, and aqueous instability. In this work, we fabricated PEDOT OECT by alternating current electrodeposition in protic ionic liquids. The steady-state characteristics were demonstrated to be stable in long-term tests. In detail, the maximum transconductance, the on/off current ratio, and the hysteresis were stable at 2.79 mS, 504, and 0.12 V, respectively. Though the transient behavior was also stable, the time constant could reach 218.6 ms. Thus, the trade-off between switching speed and stability needs to be considered in applications that require a rapid response. Full article
(This article belongs to the Special Issue Ionic Liquids for Chemical and Biochemical Applications II)
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Open AccessArticle
Globular and Fibrous Proteins Modified with Deep Eutectic Solvents: Materials for Drug Delivery
Molecules 2019, 24(19), 3583; https://doi.org/10.3390/molecules24193583 - 04 Oct 2019
Cited by 2
Abstract
Proteinaceous materials have numerous structures, many of which aid in the roles they perform. Some need to impart strength while others need elasticity or toughness. This study is the first to investigate the modification of both globular and fibrous protein, namely, zein, soy [...] Read more.
Proteinaceous materials have numerous structures, many of which aid in the roles they perform. Some need to impart strength while others need elasticity or toughness. This study is the first to investigate the modification of both globular and fibrous protein, namely, zein, soy protein and gelatin, using deep eutectic solvents (DES) to form bioplastics, which may have application in drug delivery systems. The effects of DES content on the thermal and mechanical properties of the material were determined. Zein and soy are globular proteins, which both showed a significant change in the properties by the addition of DES. Both of these materials were, however, weaker and less ductile than the starch based materials previously reported in the literature. The material made from gelatin, a fibrous protein, showed variable properties depending on how long they were in contact with each other before pressing. Conductivity and NMR measurements indicate the existence of a continuous liquid phase, which are useful in the demonstrated application of transdermal drug delivery systems. It is shown that pharmaceutical DESs can be gelled with gelatin and this method is three times faster at delivering a pharmaceutical active ingredient across the skin barrier than from a corresponding solid formulation. Full article
(This article belongs to the Special Issue Ionic Liquids for Chemical and Biochemical Applications II)
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Open AccessArticle
Epoxy-Containing Ionic Liquids with Tunable Functionality
Molecules 2019, 24(14), 2591; https://doi.org/10.3390/molecules24142591 - 17 Jul 2019
Abstract
New types of ionic liquids (ILs) with an epoxy group on a piperidinium-type cation were successfully synthesized by the simple anion exchange reaction of a solid 1-allyl-1-(oxiran-2-ylmethyl)piperidinium bromide, which was designed in this study. Unfortunately, the physicochemical properties, e.g., viscosity and ionic conductivity, [...] Read more.
New types of ionic liquids (ILs) with an epoxy group on a piperidinium-type cation were successfully synthesized by the simple anion exchange reaction of a solid 1-allyl-1-(oxiran-2-ylmethyl)piperidinium bromide, which was designed in this study. Unfortunately, the physicochemical properties, e.g., viscosity and ionic conductivity, of the ILs were inferior to those of common ILs such as 1-ethyl-3-methylimidazolium tetrafluoroborate ([C2mim][BF4]) and 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)amide ([C4mim][Tf2N]). However, the resulting ILs are of great interest as reaction intermediates: For example, the epoxy group on the cation could react with various reagents, including CO2. Consequently, the modification of the cation structure in the ILs was possible. This is particularly interesting because it is very difficult to modify commonly used ILs. The approach established in this article will provide a favorable synthetic route for creating novel functional ILs in the future. Full article
(This article belongs to the Special Issue Ionic Liquids for Chemical and Biochemical Applications II)
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Planned Papers

The below list represents only planned manuscripts. Some of these manuscripts have not been received by the Editorial Office yet. Papers submitted to MDPI journals are subject to peer-review.

Type of the paper: Communication
Tentative title: Alternating current electrodeposition of poly(3,4-ethylenedioxythiophene) from protic ionic liquids to construct organic electrochemical transistors
Authors: Jianlong Ji 1,*, Xiaoxian Zhu 1, Er Hua 2,*, Shengbo Sang 1, Zhengdong Cheng 3
Affiliations: 1 College of Information and Computer, Taiyuan University of Technology, Taiyuan 030024, China
2 Chemical Science and Engineering College, North Minzu University, Ningxia 750021, China
3 Artie McFerrin Department of Chemical Engineering, Texas A & M University, Texas 77843, USA
Abstract: Poly (3,4-ethylenedioxythiophene) (PEDOT) based organic electrochemical transistors (OECTs) are usually utilized to construct highly sensitive biosensors. In this work, the PEDOT channel-layer of the OECT was prepared by alternating current (AC) electrodeposition of ethylenedioxythiophene (EDOT) monolayer in the protic ionic liquid. The PEDOT channel-layer was prepared between the microelectrodes having a gap of 10 microns on the silicon dioxide substrate. Raman spectroscopy demonstrates that the anion of the ionic liquid was deposited as a dopant in the PEDOT channel-layer. Through this method, we obtained a high on/off ratio (1000) OECT, which was promising to be used as the low-power biosensors.

Type of the paper: Article
Tentative title: Ionic Liquid Matrices for Soft Ionization in Matrix-Assisted Laser Desorption/Ionization (MALDI)
Authors: Chih-Hao Lin, I-Chung Lu*
Affiliations: Department of Chemistry, National Chung Hsing University, Taichung City, Taiwan
Abstract: Mass spectrometry (MS) has outstanding potential in analytical chemistry these two decades. To ionize the analyte efficiently, most of the conventional ionization technique apply additional energy such as photons, heat, or the electrical potential to produce ions for mass analysis. However, these excess energies might induce fragmentation because of the increased internal energy. For example, matrix-assisted laser desorption/ionization (MALDI) employs small molecules as a matrix to absorb photon energy. The analyte is then ionized and desorbed into gas phase for sample analysis by a mass spectrometer. Although MALDI has been widely used as a soft ionization technique in mass spectrometry, it is still incapable of observing the labile biomolecule. Ionic liquids can be MALDI matrices and solvents for the analyte. It showed high stability with negligible sublimation under vacuum and excellent capability for quantitative analyses previously. In this study, we compared the conventional matrices of MALDI with ionic liquid matrices to demonstrate a softer characteristic of ionization, providing fewer fragments during the ionization processes. The results showed a potential method to observe intact biomolecules based on the ionic liquids.

Tentative title: Globular and fibrous proteins modified with deep eutectic solvents
Authors: Wanwan Qu, Riina Häkkinen, Jack Allen, Carmine D’Agostino and Andrew P. Abbott*
Affiliations:
1. School of Chemistry, University of Leicester, University Road, Leicester LE1 7RH,
2. VTT Technical Research Centre of Finland Ltd, Tietotie 4 E, FI-02150 VTT, Finland
3. School of Chemical Engineering and Analytical Science, University of Manchester, Oxford Rd, Manchester, M13 9PL, UK
Abstract: Proteinaceous materials have numerous structures, many of which aid in the roles they perform. Some need to impart strength while others need elasticity or toughness. This study is the first to investigate the modification of both globular and fibrous protein, namely, zein, soy protein and gelatin, using deep eutectic solvents (DES) to form bioplastics which may have application in drug delivery systems. The effects of DES content on the thermal and mechanical properties of the material were determined. Zein and soy are globular proteins which both showed a significant change in the properties by the addition of DES. Both of these materials were, however, weaker and less ductile than the starch based materials previously reported in the literature. The material made from gelatin, a fibrous protein, showed variable properties depending on how long they were in contact with each other before pressing. Conductivity and NMR measurements indicate the existence of a continuous phase which are useful in the demonstrated application of transdermal drug delivery systems.

Title: Comparison of Chemotherapeutic Activities of Rhodamine based GUMBOS and nanoGUMBOS
Authors: Dr. Nimisha Bhattarai,a,1 Dr. Mi Chen,a,2 Dr. Rocío L. Pérez,a Dr. Sudhir Ravula,a,3 Dr. Robert M. Strongin,b Karen McDonough,c and Dr. Isiah M. Warner a*
Affiliation: aDepartment of Chemistry, Louisiana State University, Baton Rouge, LA 70803, USA bDepartment of Chemistry, Portland State University, Portland, OR 97207, USA cAgCenter Biotechnology Labs, Louisiana State University, Baton Rouge, LA 70803, USA. 1 Present address - Department of Biochemistry and Molecular Biology, School of Medicine, Tulane University, New Orleans, LA 70118. 2 Present address – Pharmaceutical Product Development Bioanalytical Laboratory, Middleton, WI 53562. 3 Present address - Louisiana State University Health Sciences Center New Orleans, New Orleans, LA 70112. * Corresponding Author: Isiah M. Warner, email: [email protected], Phone: 225-578-2829, Fax: 225-578-3971
Abstract: Rhodamine derivatives have been widely investigated for their mitochondrial targeting and chemotherapeutic properties that result from their lipophilic cationic structures. In previous research, we have found that conversion of Rhodamine 6G into nanoGUMBOS, i.e. nanomaterials derived from a group of uniform materials based on organic salts (GUMBOS), led to selective chemotherapeutic toxicity for cancer cells over normal cells. Herein, we investigate the chemotherapeutic activity of GUMBOS derived from four different rhodamine derivatives, two bearing an ester group, i.e. Rhodamine 123 (R123) and SNAFR-5, and two bearing a carboxylic acid group, i.e. rhodamine 110 (R110) and rhodamine B (RB). In this study, we evaluate 1) relative hydrophobicity via octanol-water partition coefficients, 2) cytotoxicity, and 3) cellular uptake in order to evaluate possible structure activity relationship between these different compounds. Intriguingly, we found that while GUMBOS derived from R123 and SNAFR-5 formed nanoGUMBOS in aqueous medium, no distinct nanoparticles are observed for RB and R110 GUMBOS. Further investigation revealed that the relatively high water solubility of R110 and RB GUMBOS hinders nanoparticle formation. Subsequently, while R123 and SNAFR-5 displayed selective chemotherapeutic toxicity similar to that of previously investigated R6G nanoGUMBOS, the R110 and RB GUMBOS were lacking in this property. Additionally, the chemotherapeutic toxicities of R123 and SNAFR-5 nanoGUMBOS were also significantly greater than R110 and RB GUMBOS. Observed results were consistent with decreased cellular uptake of R110 and RB as compared to R123 and SNAFR-5 compounds. Moreover, these results are also consistent with previous observations that suggest that nanoparticle formation is critical to the observed selective chemotherapeutic properties as well as chemotherapeutic efficacy of rhodamine nanoGUMBOS.

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