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Michalski J, Cłapa T, Narożna D, Syguda A, van Oostrum P, Reimhult E. Morpholinium-based Ionic Liquids as Potent Antibiofilm and Sensitizing Agents for the Control of Pseudomonas aeruginosa. J Mol Biol 2024; 436:168627. [PMID: 38795768 DOI: 10.1016/j.jmb.2024.168627] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2024] [Revised: 05/17/2024] [Accepted: 05/20/2024] [Indexed: 05/28/2024]
Abstract
Rising antimicrobial resistance is a critical threat to worldwide public health. To address the increasing antibiotic tolerance, diverse antimicrobial agents are examined for their ability to decrease bacterial resistance. One of the most relevant and persistent human pathogens is Pseudomonas aeruginosa. Our study investigates the anti-biofilm and sensitizing activity of 12 morpholinium-based ionic liquids with herbicidal anions on four clinically relevant P. aeruginosa strains. Among all tested compounds, four ionic liquids prevented biofilm formation at sub-minimum inhibitory concentrations for all investigated strains. For the first time, we established a hormetic effect on biofilm formation for P. aeruginosa strains subjected to an ionic liquid treatment. Interestingly, while ionic liquids with 4,4-didecylmorpholinium [Dec2Mor]+ are more efficient against planktonic bacteria, 4-decyl-4-ethylmorpholinium [DecEtMor]+ showed more potent inhibition of biofilm formation. Ionic liquids with 4,4-didecylmorpholinium ([Dec2Mor]+) cations even induced biofilm formation by strain 39016 at high concentrations due to flocculation. Morpholinium-based ionic liquids were also shown to enhance the efficacy of commonly used antibiotics from different chemical groups. We demonstrate that this synergy is associated with the mode of action of the antibiotics.
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Affiliation(s)
- Jakub Michalski
- Poznań University of Life Sciences, Department of Biochemistry and Biotechnology, Dojazd 11, 60-632 Poznan, Poland
| | - Tomasz Cłapa
- Poznań University of Life Sciences, Department of Biochemistry and Biotechnology, Dojazd 11, 60-632 Poznan, Poland.
| | - Dorota Narożna
- Poznań University of Life Sciences, Department of Biochemistry and Biotechnology, Dojazd 11, 60-632 Poznan, Poland
| | - Anna Syguda
- Poznan University of Technology, Department of Chemical Technology, Berdychowo 4, 60-965 Poznan, Poland
| | - Peter van Oostrum
- BOKU University, Department of Bionanosciences, Institute of Colloid and Biointerface Science, Muthgasse 11-II, A-1090 Vienna, Austria
| | - Erik Reimhult
- BOKU University, Department of Bionanosciences, Institute of Colloid and Biointerface Science, Muthgasse 11-II, A-1090 Vienna, Austria
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2
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Benedetto A. Ionic liquids meet lipid bilayers: a state-of-the-art review. Biophys Rev 2023; 15:1909-1939. [PMID: 38192351 PMCID: PMC10771448 DOI: 10.1007/s12551-023-01173-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2023] [Accepted: 11/29/2023] [Indexed: 01/10/2024] Open
Abstract
In the past 25 years, a vast family of complex organic salts known as room-temperature ionic liquids (ILs) has received increasing attention due to their potential applications. ILs are composed by an organic cation and either an organic or inorganic anion, and possess several intriguing properties such as low vapor pressure and being liquid around room temperature. Several biological studies flagged their moderate-to-high (cyto)-toxicity. Toxicity is, however, also a synonym of affinity, and this boosted a series of biophysical and chemical-physical investigations aimed at exploiting ILs in bio-nanomedicine, drug-delivery, pharmacology, and bio-nanotechnology. Several of these investigations focused on the interaction between ILs and lipid membranes, aimed at determining the microscopic mechanisms behind their interaction. This is the focus of this review work. These studies have been carried out on a variety of different lipid bilayer systems ranging from 1-lipid to 5-lipids systems, and also on cell-extracted membranes. They have been carried out at different chemical-physical conditions and by the use of a number of different approaches, including atomic force microscopy, neutron and X-ray scattering, dynamic light scattering, differential scanning calorimetry, surface quartz microbalance, nuclear magnetic resonance, confocal fluorescence microscopy, and molecular dynamics simulations. The aim of this "2023 Michèle Auger Award" review work is to provide the reader with an up-to-date overview of this fascinating research field where "ILs meet lipid bilayers (aka biomembranes)," with the aim to boost it further and expand its cross-disciplinary edges towards novel high-impact ideas/applications in pharmacology, drug delivery, biomedicine, and bio-nanotechnology.
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Affiliation(s)
- Antonio Benedetto
- School of Physics, University College Dublin, Dublin, Ireland
- Conway Institute of Biomolecular and Biomedical Research, University College Dublin, Dublin, Ireland
- Department of Science, University of Roma Tre, Rome, Italy
- Laboratory for Neutron Scattering, Paul Scherrer Institute, Villigen, Switzerland
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3
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Beck K, Nandy J, Hoernke M. Membrane permeabilization can be crucially biased by a fusogenic lipid composition - leaky fusion caused by antimicrobial peptides in model membranes. SOFT MATTER 2023; 19:2919-2931. [PMID: 37010846 DOI: 10.1039/d2sm01691e] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
Induced membrane permeabilization or leakage is often taken as an indication for activity of membrane-active molecules, such as antimicrobial peptides (AMPs). The exact leakage mechanism is often unknown, but important, because certain mechanisms might actually contribute to microbial killing, while others are unselective, or potentially irrelevant in an in vivo situation. Using an antimicrobial example peptide (cR3W3), we illustrate one of the potentially misleading leakage mechanisms: leaky fusion, where leakage is coupled to membrane fusion. Like many others, we examine peptide-induced leakage in model vesicles consisting of binary mixtures of anionic and zwitterionic phospholipids. In fact, phosphatidylglycerol and phosphatidylethanolamine (PG/PE) are supposed to reflect bacterial membranes, but exhibit a high propensity for vesicle aggregation and fusion. We describe the implications of this vesicle fusion and aggregation for the reliability of model studies. The ambiguous role of the relatively fusogenic PE-lipids becomes clear as leakage decreases significantly when aggregation and fusion are prevented by sterical shielding. Furthermore, the mechanism of leakage changes if PE is exchanged for phosphatidylcholine (PC). We thus point out that the lipid composition of model membranes can be biased towards leaky fusion. This can lead to discrepancies between model studies and activity in true microbes, because leaky fusion is likely prevented by bacterial peptidoglycan layers. In conclusion, choosing the model membrane might implicate the type of effect (here leakage mechanism) that is observed. In the worst case, as with leaky fusion of PG/PE vesicles, this is not directly relevant for the intended antimicrobial application.
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Affiliation(s)
- Katharina Beck
- Chemistry and Pharmacy, Albert-Ludwigs-Universität, Freiburg i. Br., Germany.
| | - Janina Nandy
- Chemistry and Pharmacy, Albert-Ludwigs-Universität, Freiburg i. Br., Germany.
| | - Maria Hoernke
- Chemistry and Pharmacy, Albert-Ludwigs-Universität, Freiburg i. Br., Germany.
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4
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Shi S, Fan H, Hoernke M. Leaky membrane fusion: an ambivalent effect induced by antimicrobial polycations. NANOSCALE ADVANCES 2022; 4:5109-5122. [PMID: 36504745 PMCID: PMC9680940 DOI: 10.1039/d2na00464j] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/18/2022] [Accepted: 10/24/2022] [Indexed: 05/28/2023]
Abstract
Both antimicrobial peptides and their synthetic mimics are potential alternatives to classical antibiotics. They can induce several membrane perturbations including permeabilization. Especially in model studies, aggregation of vesicles by such polycations is often reported. Here, we show that unintended vesicle aggregation or indeed fusion can cause apparent leakage in model studies that is not possible in most microbes, thus potentially leading to misinterpretations. The interactions of a highly charged and highly selective membrane-active polycation with negatively charged phosphatidylethanolamine/phosphatidylglycerol (PE/PG) vesicles are studied by a combination of biophysical methods. At low polycation concentrations, apparent vesicle aggregation was found to involve exchange of lipids. Upon neutralization of the negatively charged vesicles by the polycation, full fusion and leakage occurred and leaky fusion is suspected. To elucidate the interplay of leakage and fusion, we prevented membrane contacts by decorating the vesicles with PEG-chains. This inhibited fusion and also leakage activity. Leaky fusion is further corroborated by increased leakage with increasing likeliness of vesicle-vesicle contacts. Because of its similar appearance to other leakage mechanisms, leaky fusion is difficult to identify and might be overlooked and more common amongst polycationic membrane-active compounds. Regarding biological activity, leaky fusion needs to be carefully distinguished from other membrane permeabilization mechanisms, as it may be less relevant to bacteria, but potentially relevant for fungi. Furthermore, leaky fusion is an interesting effect that could help in endosomal escape for drug delivery. A comprehensive step-by-step protocol for membrane permeabilization/vesicle leakage using calcein fluorescence lifetime is provided in the ESI.
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Affiliation(s)
- Shuai Shi
- Chemistry and Pharmacy, Albert-Ludwigs-Universität 79104 Freiburg i.Br. Germany
| | - Helen Fan
- Leslie Dan Faculty of Pharmacy, University of Toronto Toronto Canada
| | - Maria Hoernke
- Chemistry and Pharmacy, Albert-Ludwigs-Universität 79104 Freiburg i.Br. Germany
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5
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Shi S, Markl AM, Lu Z, Liu R, Hoernke M. Interplay of Fusion, Leakage, and Electrostatic Lipid Clustering: Membrane Perturbations by a Hydrophobic Antimicrobial Polycation. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2022; 38:2379-2391. [PMID: 35148117 DOI: 10.1021/acs.langmuir.1c03445] [Citation(s) in RCA: 6] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Membrane active compounds are able to induce various types of membrane perturbations. Natural or biomimetic candidates for antimicrobial treatment or drug delivery scenarios are mostly designed and tested for their ability to induce membrane permeabilization, also termed leakage. Furthermore, the interaction of these usually cationic amphiphiles with negatively charged vesicles often causes colloidal instability leading to vesicle aggregation or/and vesicle fusion. We show the interplay of these modes of membrane perturbation in mixed phosphatidyl glycerol (PG)/phosphatidyl ethanolamine (PE) by the statistical copolymer MM:CO comprising, both, charged and hydrophobic subunits. MM:CO is a representative of partially hydrophobic, highly active, but less selective antimicrobial polycations. Cryo-electron microscopy indicates vesicle fusion rather than vesicle aggregation upon the addition of MM:CO to negatively charged PG/PE (1:1) vesicles. In a combination of fluorescence-based leakage and fusion assays, there is support for membrane permeabilization and pronounced vesicle fusion activity as distinct effects. To this end, membrane fusion and aggregation were prevented by including lipids with polyethylene glycol attached to their head groups (PEG-lipids). The leakage activity of MM:CO is very similar in the absence and presence of PEG-lipids. Vesicle aggregation and fusion however are largely suppressed. This strongly suggests that MM:CO induces leakage by asymmetric packing stress because of hydrophobically driven interactions which could lead to leakage. As a further membrane perturbation effect, MM:CO causes lipid clustering in model vesicles. We address potential artifacts and misinterpretations of experiments characterizing leakage and fusion. Additional to the leakage activity, the pronounced fusogenic activity of the polymer and potentially of many other similar compounds likely has implications for antimicrobial activity and beyond.
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Affiliation(s)
- Shuai Shi
- Chemistry and Pharmacy, Albert-Ludwigs-Universität, 79104 Freiburg i.Br., Germany
| | - Anja Madleine Markl
- Chemistry and Pharmacy, Albert-Ludwigs-Universität, 79104 Freiburg i.Br., Germany
| | - Ziyi Lu
- State Key Laboratory of Bioreactor Engineering, Key Laboratory for Ultrafine Materials of Ministry of Education, Frontiers Science Center for Materiobiology and Dynamic Chemistry, Research Center for Biomedical Materials of Ministry of Education, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237, China
| | - Runhui Liu
- State Key Laboratory of Bioreactor Engineering, Key Laboratory for Ultrafine Materials of Ministry of Education, Frontiers Science Center for Materiobiology and Dynamic Chemistry, Research Center for Biomedical Materials of Ministry of Education, School of Materials Science and Engineering, East China University of Science and Technology, Shanghai 200237, China
| | - Maria Hoernke
- Chemistry and Pharmacy, Albert-Ludwigs-Universität, 79104 Freiburg i.Br., Germany
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6
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Rita Pereira A, Gomes IB, Simões M. Choline-based ionic liquids for planktonic and biofilm growth control of Bacillus cereus and Pseudomonas fluorescens. J Mol Liq 2022. [DOI: 10.1016/j.molliq.2021.117077] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/20/2022]
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7
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Hitchner MA, Necelis MR, Shirley D, Caputo GA. Effect of Non-natural Hydrophobic Amino Acids on the Efficacy and Properties of the Antimicrobial Peptide C18G. Probiotics Antimicrob Proteins 2021; 13:527-541. [PMID: 32889698 PMCID: PMC7933317 DOI: 10.1007/s12602-020-09701-3] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
Antimicrobial peptides (AMPs) have been an area of great interest, due to the high selectivity of these molecules toward bacterial targets over host cells and the limited development of bacterial resistance to these molecules through evolution. The peptides are known to selectively bind to bacterial cell surfaces through electrostatic interactions, and subsequently, the peptides insert into the cell membrane and cause local disruptions of membrane integrity leading to cell death. Previous experiments showed that replacing the Leu residues in the AMP C18G with other naturally occurring hydrophobic residues resulted in side-chain-dependent activities. This work extends the investigation to non-natural hydrophobic amino acids and the effect on peptide activity. Minimal inhibitory concentration (MIC) results demonstrated that amino acid substitutions containing long flexible carbon chains maintained or increased antimicrobial activity compared to natural analogues. In solution, the peptide showed aggregation only with the most hydrophobic non-natural amino acid substitutions. Binding assays using Trp fluorescence confirm a binding preference for anionic lipids while quenching experiments demonstrated that the more hydrophobic peptides are more deeply buried in the anionic lipid bilayers compared to the zwitterionic bilayers. The most effective peptides at killing bacteria were also those which showed some level of disruption of bacterial membranes; however, one peptide sequence exhibited very strong activity and very low levels of red blood cell hemolysis, yielding a promising target for future development.
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Affiliation(s)
- Morgan A Hitchner
- Department of Chemistry and Biochemistry, Rowan University, 201 Mullica Hill Road, Glassboro, NJ, 08028, USA
| | - Matthew R Necelis
- Department of Chemistry and Biochemistry, Rowan University, 201 Mullica Hill Road, Glassboro, NJ, 08028, USA
| | - Devanie Shirley
- Department of Chemistry and Biochemistry, Rowan University, 201 Mullica Hill Road, Glassboro, NJ, 08028, USA
| | - Gregory A Caputo
- Department of Chemistry and Biochemistry, Rowan University, 201 Mullica Hill Road, Glassboro, NJ, 08028, USA.
- Department of Molecular and Cellular Biosciences, Rowan University, 201 Mullica Hill Road, Glassboro, NJ, 08028, USA.
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8
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Simões M, Pereira AR, Simões LC, Cagide F, Borges F. Biofilm control by ionic liquids. Drug Discov Today 2021; 26:1340-1346. [PMID: 33549827 DOI: 10.1016/j.drudis.2021.01.031] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2020] [Revised: 01/19/2021] [Accepted: 01/29/2021] [Indexed: 10/22/2022]
Abstract
Ionic liquids (ILs) are remarkable chemical compounds with applications in many areas of modern science. They are increasingly recognized as promising compounds to fight microorganisms in both planktonic and biofilm states, contributing to reinvent the antimicrobial pipeline. Biofilm-related infections are particularly challenging given that the scientific community has not yet identified a reliable control strategy. Understanding of the action of ILs in biofilm control is is still in a very early stage. However, given the highly tunable nature and exceptional properties of ILs, they are excellent candidates for biofilm control. Here, we review the major advances in, and challenges tothe use of ILs for effective biofilm control.
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Affiliation(s)
- Manuel Simões
- LEPABE, Department of Chemical Engineering, Faculty of Engineering, University of Porto, 4200-465 Porto, Portugal.
| | - Ana Rita Pereira
- LEPABE, Department of Chemical Engineering, Faculty of Engineering, University of Porto, 4200-465 Porto, Portugal
| | - Lúcia Chaves Simões
- CEB, Centre of Biological Engineering, University of Minho, Campus de Gualtar 4710-057 Braga, Portugal
| | - Fernando Cagide
- CIQUP, Department of Chemistry and Biochemistry, Faculty of Sciences, University of Porto, 4169-007 Porto, Portugal
| | - Fernanda Borges
- CIQUP, Department of Chemistry and Biochemistry, Faculty of Sciences, University of Porto, 4169-007 Porto, Portugal.
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9
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Yang DD, Paterna NJ, Senetra AS, Casey KR, Trieu PD, Caputo GA, Vaden TD, Carone BR. Synergistic interactions of ionic liquids and antimicrobials improve drug efficacy. iScience 2021; 24:101853. [PMID: 33364575 PMCID: PMC7753145 DOI: 10.1016/j.isci.2020.101853] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2020] [Revised: 10/08/2020] [Accepted: 11/18/2020] [Indexed: 01/16/2023] Open
Abstract
Combinations of ionic liquids (ILs) with antimicrobial compounds have been shown to produce synergistic activities in model liposomes. In this study, imidazolium chloride-based ILs with alkyl tail length variations are combined with commercially available, small-molecule antimicrobials to examine the potential for combinatorial and synergistic antimicrobial effects on P. aeruginosa, E. coli, S. aureus, and S. cerevisiae. The effects of these treatments in a human cell culture model indicate the cytotoxic limits of ILs paired with antimicrobials. The analysis of these ILs demonstrates that the length of the alkyl chain on the IL molecule is proportional to both antimicrobial activity and cytotoxicity. Moreover, the ILs which exhibit synergy with small-molecule antibiotics appear to be acting in a membrane permeabilizing manner. Collectively, results from these experiments demonstrate an increase in antimicrobial efficacy with specific IL + antimicrobial combinations on microbial cultures while maintaining low cytotoxicity in a mammalian cell culture model.
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Affiliation(s)
- Daniel D. Yang
- Department of Chemistry and Biochemistry, Rowan University, 201 Mullica Hill Road, Glassboro, NJ 08028, USA
| | - Nicholas J. Paterna
- Department of Chemistry and Biochemistry, Rowan University, 201 Mullica Hill Road, Glassboro, NJ 08028, USA
| | - Alexandria S. Senetra
- Department of Chemistry and Biochemistry, Rowan University, 201 Mullica Hill Road, Glassboro, NJ 08028, USA
| | - Kaitlyn R. Casey
- Department of Molecular and Cellular Biosciences, Rowan University, 201 Mullica Hill Road, Glassboro, NJ 08028, USA
| | - Phillip D. Trieu
- Department of Chemistry and Biochemistry, Rowan University, 201 Mullica Hill Road, Glassboro, NJ 08028, USA
| | - Gregory A. Caputo
- Department of Chemistry and Biochemistry, Rowan University, 201 Mullica Hill Road, Glassboro, NJ 08028, USA
- Department of Molecular and Cellular Biosciences, Rowan University, 201 Mullica Hill Road, Glassboro, NJ 08028, USA
| | - Timothy D. Vaden
- Department of Chemistry and Biochemistry, Rowan University, 201 Mullica Hill Road, Glassboro, NJ 08028, USA
| | - Benjamin R. Carone
- Department of Molecular and Cellular Biosciences, Rowan University, 201 Mullica Hill Road, Glassboro, NJ 08028, USA
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10
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Takahashi H, Caputo GA, Kuroda K. Amphiphilic polymer therapeutics: an alternative platform in the fight against antibiotic resistant bacteria. Biomater Sci 2021; 9:2758-2767. [DOI: 10.1039/d0bm01865a] [Citation(s) in RCA: 18] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
Amphiphilic antimicrobial polymers show promising potential as polymer therapeutics to fight drug resistant bacteria and biofilms.
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Affiliation(s)
- Haruko Takahashi
- Graduate School of Integrated Sciences for Life
- Hiroshima University
- Hiroshima 739-8526
- Japan
| | | | - Kenichi Kuroda
- Department of Biologic and Materials Sciences
- School of Dentistry
- University of Michigan
- Ann Arbor
- USA
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11
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Amaral M, Pereiro AB, Gaspar MM, Reis CP. Recent advances in ionic liquids and nanotechnology for drug delivery. Nanomedicine (Lond) 2020; 16:63-80. [PMID: 33356551 DOI: 10.2217/nnm-2020-0340] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
In drug discovery and drug development, it is estimated that around 40% of commercialized and 90% of under-study drugs have inadequate pharmaceutical properties, severely impairing its therapeutic efficacy. Thus, there is a strong demand to find strategies to enhance the delivery of such drugs. Ionic liquids are a novel class of liquids composed of a combination of organic salts that are of particular interest alone or in combination with drug delivery systems. This review is focused on the recent efforts using ionic liquids in drug solubility, formulation and drug delivery with specific emphasis on nanotechnology. The latest developments using hybrid delivery systems obtained upon the combination of drug delivery systems and ionic liquids will also be addressed.
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Affiliation(s)
- Mariana Amaral
- Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Universidade de Lisboa, Lisboa, 1649-003, Portugal
| | - Ana B Pereiro
- LAQV, REQUIMTE, Department of Chemistry, Faculdade de Ciências e Tecnologia, Universidade Nova de Lisboa, Caparica, 2829-516, Portugal
| | - Maria Manuela Gaspar
- Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Universidade de Lisboa, Lisboa, 1649-003, Portugal
| | - Catarina Pinto Reis
- Research Institute for Medicines (iMed.ULisboa), Faculty of Pharmacy, Universidade de Lisboa, Lisboa, 1649-003, Portugal.,IBEB, Institute of Biophysics & Biomedical Engineering, Faculdade de Ciências, Universidade de Lisboa, Lisboa, 1749-016, Portugal
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12
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Florio W, Rizzato C, Becherini S, Guazzelli L, D'Andrea F, Lupetti A. Synergistic activity between colistin and the ionic liquids 1-methyl-3-dodecylimidazolium bromide, 1-dodecyl-1-methylpyrrolidinium bromide, or 1-dodecyl-1-methylpiperidinium bromide against Gram-negative bacteria. J Glob Antimicrob Resist 2020; 21:99-104. [PMID: 32298808 DOI: 10.1016/j.jgar.2020.03.022] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/11/2019] [Revised: 03/19/2020] [Accepted: 03/23/2020] [Indexed: 01/23/2023] Open
Abstract
OBJECTIVES Ionic liquids have shown potential for applications as antimicrobials. Their antimicrobial activity has been shown to be higher against Gram-positive than Gram-negative bacteria, suggesting a protective role for the outer membrane of Gram-negative microorganisms. Colistin is a last-resort antibiotic often used for treating infections caused by multi-drug resistant Gram-negative bacteria. Colistin interacts with the bacterial lipopolysaccharide, thus altering the structure and increasing the permeability of the outer membrane. The aim of this study was to investigate the interaction between colistin and the ionic liquids 1-methyl-3-dodecylimidazolium bromide, 1-dodecyl-1-methylpyrrolidinium bromide, and 1-dodecyl-1-methylpiperidinium bromide against Gram-negative bacteria of clinical importance such as Escherichia coli, Klebsiella pneumoniae, Pseudomonas aeruginosa, and Acinetobacter baumannii. METHODS The interaction between colistin and ionic liquids against Gram-negative bacteria was evaluated by the checkerboard assay. Bacterial killing assays against P. aeruginosa were carried out to assess whether the synergistic combinations were bactericidal. RESULTS The results of checkerboard assays showed that all three ionic liquids interacted synergistically with colistin against K. pneumoniae, P. aeruginosa, and A. baumannii but not against E. coli, which was more sensitive to all three ionic liquids compared with the other tested species. The synergistic combinations showed no haemolytic activity. Bacterial killing assays showed that the synergistic effect between colistin and each one of the three tested ionic liquids against P. aeruginosa was bactericidal. CONCLUSION Overall, the results obtained suggest that colistin and ionic liquids might be used in combination for possible applications to combat infections caused by multi-drug resistant Gram-negative bacteria.
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Affiliation(s)
- Walter Florio
- Dipartimento di Ricerca Traslazionale e delle Nuove Tecnologie in Medicina e Chirurgia, Università di Pisa, Via San Zeno 37-39, 56127, Pisa, Italy.
| | - Cosmeri Rizzato
- Dipartimento di Ricerca Traslazionale e delle Nuove Tecnologie in Medicina e Chirurgia, Università di Pisa, Via San Zeno 37-39, 56127, Pisa, Italy.
| | - Stefano Becherini
- Dipartimento di Farmacia, Università di Pisa, Via Bonanno Pisano 6, 56126, Pisa, Italy.
| | - Lorenzo Guazzelli
- Dipartimento di Farmacia, Università di Pisa, Via Bonanno Pisano 6, 56126, Pisa, Italy.
| | - Felicia D'Andrea
- Dipartimento di Farmacia, Università di Pisa, Via Bonanno Pisano 6, 56126, Pisa, Italy.
| | - Antonella Lupetti
- Dipartimento di Ricerca Traslazionale e delle Nuove Tecnologie in Medicina e Chirurgia, Università di Pisa, Via San Zeno 37-39, 56127, Pisa, Italy.
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13
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Jiang K, Liu X, He H, Wang J, Zhang S. Insight into the formation and permeability of ionic liquid unilamellar vesicles by molecular dynamics simulation. SOFT MATTER 2020; 16:2605-2610. [PMID: 32096807 DOI: 10.1039/c9sm02339a] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Unilamellar vesicles in solution could open up new horizons for reaction and material delivery, but the formation mechanism especially for the permeability of the small molecule through the vesicle membrane is still unknown. In this study, the formation and permeability of the unilamellar vesicles formed by the ionic liquid 1-dodecyl-3-methylimidazolium salicylate ([C12mim][Sal]) have been investigated by molecular dynamics simulation. Starting from a random distribution of ionic liquids, the entire process of vesicle formation could be observed on a nanosecond time scale, during which planar and cup-like structures are formed at the intermediate stage. Energy analysis reveals that the electrostatic interactions between cations and anions play a dominant role in forming and stabilizing the vesicle. Radial density distribution functions indicate that the final stable vesicle is a spherical bilayer structure. Besides, it was found that the structure of vesicles is maintained with the increase of temperature, while the water molecules in the vesicles could be completely exchanged quickly. These results suggest that vesicles may be beneficial for the enrichment or release of molecules.
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Affiliation(s)
- Kun Jiang
- School of Chemistry and Chemical Engineering, Qingdao University, Qingdao 266071, Shandong, China.
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14
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Acharyya A, DiGiuseppi D, Stinger BL, Schweitzer-Stenner R, Vaden TD. Structural Destabilization of Azurin by Imidazolium Chloride Ionic Liquids in Aqueous Solution. J Phys Chem B 2019; 123:6933-6945. [DOI: 10.1021/acs.jpcb.9b04113] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023]
Affiliation(s)
- Arusha Acharyya
- Department of Chemistry, University of Pennsylvania, 231 S. 34 Street, Philadelphia, Pennsylvania 19104, United States
| | - David DiGiuseppi
- Department of Chemistry, Drexel University, 32 S. 32nd Street, Philadelphia, Pennsylvania 19104, United States
| | - Brittany L. Stinger
- Department of Chemistry and Biochemistry, Rowan University, 201 Mullica Hill Road, Glassboro, New Jersey 08028, United States
| | - Reinhard Schweitzer-Stenner
- Department of Chemistry, Drexel University, 32 S. 32nd Street, Philadelphia, Pennsylvania 19104, United States
| | - Timothy D. Vaden
- Department of Chemistry and Biochemistry, Rowan University, 201 Mullica Hill Road, Glassboro, New Jersey 08028, United States
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Lee JY, Selfridge KM, Kohn EM, Vaden TD, Caputo GA. Effects of Ionic Liquid Alkyl Chain Length on Denaturation of Myoglobin by Anionic, Cationic, and Zwitterionic Detergents. Biomolecules 2019; 9:biom9070264. [PMID: 31288435 PMCID: PMC6681400 DOI: 10.3390/biom9070264] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2019] [Revised: 06/30/2019] [Accepted: 07/01/2019] [Indexed: 12/19/2022] Open
Abstract
The unique electrochemical properties of ionic liquids (ILs) have motivated their use as solvents for organic synthesis and green energy applications. More recently, their potential in pharmaceutical chemistry has prompted investigation into their effects on biomolecules. There is evidence that some ILs can destabilize proteins via a detergent-like manner; however, the mechanism still remains unknown. Our hypothesis is that if ILs are denaturing proteins via a detergent-like mechanism, detergent-mediated protein unfolding should be enhanced in the presence of ILs. The properties of myoglobin was examined in the presence of a zwitterionic (N,N-dimethyl-N-dodecylglycine betaine (Empigen BB®, EBB)), cationic (tetradecyltrimethylammonium bromide (TTAB)), and anionic (sodium dodecyl sulfate (SDS)) detergent as well as ILs based on alkylated imidazolium chlorides. Protein structure was measured through a combination of absorbance, fluorescence, and circular dichroism (CD) spectroscopy: absorbance and CD were used to monitor heme complexation to myoglobin, and tryptophan fluorescence quenching was used as an indicator for heme dissociation. Notably, the detergents tested did not fully denature the protein but instead resulted in loss of the heme group. At low IL concentrations, heme dissociation remained a traditional, cooperative process; at high concentrations, ILs with increased detergent-like character exhibited a more complex pattern, which is most likely attributable to micellization of the ionic liquids or direct denaturation or heme dissociation induced by the ILs. These trends were consistent across all species of detergents. 1,6-diphenyl-1,3,5-hexatriene (DPH) fluorescence was further used to characterize micelle formation in aqueous solutions containing detergent and ionic liquid. The dissociation thermodynamics show that EBB- and TTAB-induced dissociation of heme is not significantly impacted by room temperature ionic liquids (RTILs), whereas SDS-induced dissociation is more dramatically impacted by all RTILs examined. Together, these results indicate a complex interaction of detergents, likely based on headgroup charge, and the active component of RTILs to influence heme dissociation and potentially protein denaturation.
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Affiliation(s)
- Joshua Y Lee
- Department of Chemistry and Biochemistry, Rowan University, Glassboro, NJ 08028, USA
- Bantivoglio Honors College, Rowan University, Glassboro, NJ 08028, USA
| | - Katherine M Selfridge
- Department of Chemistry and Biochemistry, Rowan University, Glassboro, NJ 08028, USA
| | - Eric M Kohn
- Department of Chemistry and Biochemistry, Rowan University, Glassboro, NJ 08028, USA
- Bantivoglio Honors College, Rowan University, Glassboro, NJ 08028, USA
| | - Timothy D Vaden
- Department of Chemistry and Biochemistry, Rowan University, Glassboro, NJ 08028, USA
| | - Gregory A Caputo
- Department of Chemistry and Biochemistry, Rowan University, Glassboro, NJ 08028, USA.
- Department of Molecular and Cellular Biosciences, Rowan University, Glassboro, NJ 08028 USA.
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16
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Correlating Lipid Membrane Permeabilities of Imidazolium Ionic Liquids with their Cytotoxicities on Yeast, Bacterial, and Mammalian Cells. Biomolecules 2019; 9:biom9060251. [PMID: 31242711 PMCID: PMC6627299 DOI: 10.3390/biom9060251] [Citation(s) in RCA: 28] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2019] [Revised: 06/19/2019] [Accepted: 06/21/2019] [Indexed: 02/06/2023] Open
Abstract
Alkyl-imidazolium chloride ionic liquids (ILs) have been broadly studied for biochemical and biomedical technologies. They can permeabilize lipid bilayer membranes and have cytotoxic effects, which makes them targets for drug delivery biomaterials. We assessed the lipid-membrane permeabilities of ILs with increasing alkyl chain lengths from ethyl to octyl groups on large unilamellar vesicles using a trapped-fluorophore fluorescence lifetime-based leakage experiment. Only the most hydrophobic IL, with the octyl chain, permeabilizes vesicles, and the concentration required for permeabilization corresponds to its critical micelle concentration. To correlate the model vesicle studies with biological cells, we quantified the IL permeabilities and cytotoxicities on different cell lines including bacterial, yeast, and ovine blood cells. The IL permeabilities on vesicles strongly correlate with permeabilities and minimum inhibitory concentrations on biological cells. Despite exhibiting a broad range of lipid compositions, the ILs appear to have similar effects on the vesicles and cell membranes.
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17
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Hitchner MA, Santiago-Ortiz LE, Necelis MR, Shirley DJ, Palmer TJ, Tarnawsky KE, Vaden TD, Caputo GA. Activity and characterization of a pH-sensitive antimicrobial peptide. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2019; 1861:182984. [PMID: 31075228 DOI: 10.1016/j.bbamem.2019.05.006] [Citation(s) in RCA: 22] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/23/2018] [Revised: 12/20/2018] [Accepted: 01/06/2019] [Indexed: 12/11/2022]
Abstract
Antimicrobial peptides (AMPs) have been an area of great interest, due to the high selectivity of these molecules toward bacterial targets over host cells and the limited development of bacterial resistance to these molecules throughout evolution. Previous work showed that when Histidine was incorporated into the peptide C18G it lost antimicrobial activity. The role of pH on activity and biophysical properties of the peptide was investigated to explain this phenomenon. Minimal inhibitory concentration (MIC) results demonstrated that decreased media pH increased antimicrobial activity. Trichloroethanol (TCE) quenching and red-edge excitation spectroscopy (REES) showed a clear pH dependence on peptide aggregation in solution. Trp fluorescence was used to monitor binding to lipid vesicles and demonstrated the peptide binds to anionic bilayers at all pH values tested, however, binding to zwitterionic bilayers was enhanced at pH 7 and 8 (above the His pKa). Dual Quencher Analysis (DQA) confirmed the peptide inserted more deeply in PC:PG and PE:PG membranes, but could insert into PC bilayers at pH conditions above the His pKa. Bacterial membrane permeabilization assays which showed enhanced membrane permeabilization at pH 5 and 6 but vesicle leakage assays indicate enhanced permeabilization of PC and PC:PG bilayers at neutral pH. The results indicate the ionization of the His side chain affects the aggregation state of the peptide in solution and the conformation the peptide adopts when bound to bilayers, but there are likely more subtle influences of lipid composition and properties that impact the ability of the peptide to form pores in membranes.
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Affiliation(s)
- Morgan A Hitchner
- Department of Chemistry and Biochemistry, Rowan University, 201 Mullica Hill Road, Glassboro, NJ 08028, United States of America
| | - Luis E Santiago-Ortiz
- Department of Chemistry and Biochemistry, Rowan University, 201 Mullica Hill Road, Glassboro, NJ 08028, United States of America
| | - Matthew R Necelis
- Department of Chemistry and Biochemistry, Rowan University, 201 Mullica Hill Road, Glassboro, NJ 08028, United States of America
| | - David J Shirley
- Department of Chemistry and Biochemistry, Rowan University, 201 Mullica Hill Road, Glassboro, NJ 08028, United States of America
| | - Thaddeus J Palmer
- Department of Chemistry and Biochemistry, Rowan University, 201 Mullica Hill Road, Glassboro, NJ 08028, United States of America
| | - Katharine E Tarnawsky
- Department of Chemistry and Biochemistry, Rowan University, 201 Mullica Hill Road, Glassboro, NJ 08028, United States of America
| | - Timothy D Vaden
- Department of Chemistry and Biochemistry, Rowan University, 201 Mullica Hill Road, Glassboro, NJ 08028, United States of America
| | - Gregory A Caputo
- Department of Chemistry and Biochemistry, Rowan University, 201 Mullica Hill Road, Glassboro, NJ 08028, United States of America; Department of Molecular and Cellular Biosciences, Rowan University, 201 Mullica Hill Road, Glassboro, NJ 08028, United States of America.
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18
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Xu WG, Qi WS, Zhang ZH, Tong J. Volumetric and viscometric investigation of aqueous solution of [Bmim][BF4] from 288.15 to 318.15 K. J Mol Liq 2019. [DOI: 10.1016/j.molliq.2019.01.057] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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19
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Sidat Z, Marimuthu T, Kumar P, du Toit LC, Kondiah PPD, Choonara YE, Pillay V. Ionic Liquids as Potential and Synergistic Permeation Enhancers for Transdermal Drug Delivery. Pharmaceutics 2019; 11:E96. [PMID: 30813375 PMCID: PMC6409523 DOI: 10.3390/pharmaceutics11020096] [Citation(s) in RCA: 75] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2018] [Revised: 02/07/2019] [Accepted: 02/15/2019] [Indexed: 11/16/2022] Open
Abstract
Transdermal drug delivery systems (TDDS) show clear advantages over conventional routes of drug administration. Nonetheless, there are limitations to current TDDS which warrant further research to improve current TDD platforms. Spurred by the synthesis of novel biodegradable ionic liquids (ILs) and favorable cytotoxicity studies, ILs were shown to be a possible solution to overcome these challenges. Their favorable application in overcoming challenges ranging from synthesis, manufacture, and even therapeutic benefits were documented. In this review, said ILs are highlighted and their role in TDDS is reviewed in terms of (a) ILs as permeation enhancers (single agents or combined), (b) ILs in drug modification, and (c) ILs as active pharmaceutical ingredients. Furthermore, future combination of ILs with other chemical permeation enhancers (CPEs) is proposed and discussed.
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Affiliation(s)
- Zainul Sidat
- Wits Advanced Drug Delivery Platform Research Unit, Department of Pharmacy and Pharmacology, School of Therapeutic Sciences, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, 7 York Road, Parktown 2193, South Africa.
| | - Thashree Marimuthu
- Wits Advanced Drug Delivery Platform Research Unit, Department of Pharmacy and Pharmacology, School of Therapeutic Sciences, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, 7 York Road, Parktown 2193, South Africa.
| | - Pradeep Kumar
- Wits Advanced Drug Delivery Platform Research Unit, Department of Pharmacy and Pharmacology, School of Therapeutic Sciences, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, 7 York Road, Parktown 2193, South Africa.
| | - Lisa C du Toit
- Wits Advanced Drug Delivery Platform Research Unit, Department of Pharmacy and Pharmacology, School of Therapeutic Sciences, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, 7 York Road, Parktown 2193, South Africa.
| | - Pierre P D Kondiah
- Wits Advanced Drug Delivery Platform Research Unit, Department of Pharmacy and Pharmacology, School of Therapeutic Sciences, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, 7 York Road, Parktown 2193, South Africa.
| | - Yahya E Choonara
- Wits Advanced Drug Delivery Platform Research Unit, Department of Pharmacy and Pharmacology, School of Therapeutic Sciences, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, 7 York Road, Parktown 2193, South Africa.
| | - Viness Pillay
- Wits Advanced Drug Delivery Platform Research Unit, Department of Pharmacy and Pharmacology, School of Therapeutic Sciences, Faculty of Health Sciences, University of the Witwatersrand, Johannesburg, 7 York Road, Parktown 2193, South Africa.
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20
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Effects of Hydrophobic Amino Acid Substitutions on Antimicrobial Peptide Behavior. Probiotics Antimicrob Proteins 2019; 10:408-419. [PMID: 29103131 DOI: 10.1007/s12602-017-9345-z] [Citation(s) in RCA: 66] [Impact Index Per Article: 13.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Abstract
Antimicrobial peptides (AMPs) are naturally occurring components of the immune system that act against bacteria in a variety of organisms throughout the evolutionary hierarchy. There have been many studies focused on the activity of AMPs using biophysical and microbiological techniques; however, a clear and predictive mechanism toward determining if a peptide will exhibit antimicrobial activity is still elusive, in addition to the fact that the mechanism of action of AMPs has been shown to vary between peptides, targets, and experimental conditions. Nonetheless, the majority of AMPs contain hydrophobic amino acids to facilitate partitioning into bacterial membranes and a net cationic charge to promote selective binding to the anionic surfaces of bacteria over the zwitterionic host cell surfaces. This study explores the role of hydrophobic amino acids using the peptide C18G as a model system. These changes were evaluated for the effects on antimicrobial activity, peptide-lipid interactions using Trp fluorescence spectroscopy, peptide secondary structure formation, and bacterial membrane permeabilization. The results show that while secondary structure formation was not significantly impacted by the substitutions, antibacterial activity and binding to model lipid membranes were well correlated. The variants containing Leu or Phe as the sole hydrophobic groups bound bilayers with highest affinity and were most effective at inhibiting bacterial growth. Peptides with Ile exhibited intermediate behavior while those with Val or α-aminoisobutyric acid (Aib) showed poor binding and activity. The Leu, Phe, and Ile peptides demonstrated a clear preference for anionic bilayers, exhibiting significant emission spectrum shifts upon binding. Similarly, the Leu, Phe, and Ile peptides demonstrated greater ability to disrupt lipid vesicles and bacterial membranes. In total, the data indicate that hydrophobic moieties in the AMP sequence play a significant role in the binding and ability of the peptide to exhibit antibacterial activity.
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21
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Egorova KS, Ananikov VP. Fundamental importance of ionic interactions in the liquid phase: A review of recent studies of ionic liquids in biomedical and pharmaceutical applications. J Mol Liq 2018. [DOI: 10.1016/j.molliq.2018.09.025] [Citation(s) in RCA: 82] [Impact Index Per Article: 13.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022]
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22
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Frank-Bertoncelj M, Pisetsky DS, Kolling C, Michel BA, Gay RE, Jüngel A, Gay S. TLR3 Ligand Poly(I:C) Exerts Distinct Actions in Synovial Fibroblasts When Delivered by Extracellular Vesicles. Front Immunol 2018; 9:28. [PMID: 29434584 PMCID: PMC5797482 DOI: 10.3389/fimmu.2018.00028] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2017] [Accepted: 01/04/2018] [Indexed: 01/03/2023] Open
Abstract
Extracellular vesicles (EV) can modulate the responses of cells to toll-like receptor (TLR) ligation; conversely, TLR ligands such as double-stranded RNA (dsRNA) can enhance the release of EV and influence of the composition and functions of EV cargos. Inflamed synovial joints in rheumatoid arthritis (RA) are rich in EV and extracellular RNA; besides, RNA released from necrotic synovial fluid cells can activate the TLR3 signaling in synovial fibroblasts (SFs) from patients with RA. Since EV occur prominently in synovial joints in RA and may contribute to the pathogenesis, we questioned whether EV can interact with dsRNA, a TLR3 ligand, and modify its actions in arthritis. We have used as model the effects on RA SFs, of EV released from monocyte U937 cells and peripheral blood mononuclear cells upon stimulation with Poly(I:C), a synthetic analog of dsRNA. We show that EV released from unstimulated cells and Poly(I:C)-stimulated U937 cells [Poly(I:C) EV] differ in size but bind similar amounts of Annexin V and express comparable levels of MAC-1, the receptor for dsRNA, on the vesicular membranes. Specifically, Poly(I:C) EV contain or associate with Poly(I:C) and at least partially protect Poly(I:C) from RNAse III degradation. Poly(I:C) EV shuttle Poly(I:C) to SFs and reproduce the proinflammatory and antiviral gene responses of SFs to direct stimulation with Poly(I:C). Poly(I:C) EV, however, halt the death receptor-induced apoptosis in SFs, thereby inverting the proapoptotic nature of Poly(I:C). These prosurvival effects sharply contrast with the high toxicity of cationic liposome-delivered Poly(I:C) and may reflect the route of Poly(I:C) delivery via EV or the fine-tuning of Poly(I:C) actions by molecular cargo in EV. The demonstration that EV may safeguard extracellular dsRNA and allow dsRNA to exert antiapoptotic effects on SFs highlights the potential of EV to amplify the pathogenicity of dsRNA in arthritis beyond inflammation (by concurrently enhancing the expansion of the invasive synovial stroma).
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Affiliation(s)
- Mojca Frank-Bertoncelj
- Center of Experimental Rheumatology, Department of Rheumatology, University Hospital Zurich, Schlieren, Switzerland
| | - David S Pisetsky
- Department of Medicine, Duke University Medical Center, Durham, NC, United States.,Medical Research Service, Durham VA Medical Center (VHA), Durham, NC, United States
| | | | - Beat A Michel
- Center of Experimental Rheumatology, Department of Rheumatology, University Hospital Zurich, Schlieren, Switzerland
| | - Renate E Gay
- Center of Experimental Rheumatology, Department of Rheumatology, University Hospital Zurich, Schlieren, Switzerland
| | - Astrid Jüngel
- Center of Experimental Rheumatology, Department of Rheumatology, University Hospital Zurich, Schlieren, Switzerland
| | - Steffen Gay
- Center of Experimental Rheumatology, Department of Rheumatology, University Hospital Zurich, Schlieren, Switzerland
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