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Gong H, Hu X, Zhang L, Fa K, Liao M, Liu H, Fragneto G, Campana M, Lu JR. How do antimicrobial peptides disrupt the lipopolysaccharide membrane leaflet of Gram-negative bacteria? J Colloid Interface Sci 2023; 637:182-192. [PMID: 36701864 DOI: 10.1016/j.jcis.2023.01.051] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2022] [Revised: 12/24/2022] [Accepted: 01/10/2023] [Indexed: 01/15/2023]
Abstract
HYPOTHESIS It is widely regarded that antimicrobial peptides (AMPs) kill bacteria by physically disrupting microbial membranes and causing cytoplasmic leakage, but it remains unclear how AMPs disrupt the outer membrane (OM) of Gram-negative bacteria (GNB) and then compromise the inner membrane. We hypothesise that different AMPs impose different structural disruptions, with direct implications to their antimicrobial efficacies. EXPERIMENTS The antimicrobial activities of three typical AMPs, including the designed short AMP, G3, and two natural AMPs, melittin and LL37, against E. coli and their haemolytic activities were studied. Lipopolysaccharide (LPS) and anionic di-palmitoyl phosphatidyl glycerol (DPPG) monolayer models were constructed to mimic the outer membrane and inner membrane leaflets of Gram-negative bacteria. The binding and penetration of AMPs to the model lipid monolayers were systematically studied by neutron reflection via multiple H/D contrast variations. FINDING G3 has relatively high antimicrobial activity, low cytotoxicity, and high proteolytic stability, whilst melittin has significant haemolysis and LL37 has weaker antimicrobial activity. G3 could rapidly lyse LPS and DPPG monolayers within 10-20 min. In contrast, melittin was highly active against the LPS membrane, but the dynamic process lasted up to 80 min, with excessive stacking in the OM. LL37 caused rather weak destruction to LPS and DPPG monolayers, leading to massive adsorption on the membrane surface without penetrating the lipid tail region. These findings demonstrate that the rationally designed AMP G3 was well optimised to impose most effective destruction to bacterial membranes, consistent with its highest bactericidal activity. These different interfacial structural features associated with AMP binding shed light on the future development of active and biocompatible AMPs for infection and wound treatments.
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Affiliation(s)
- Haoning Gong
- Biological Physics Laboratory, Department of Physics and Astronomy, Faculty of Science and Engineering, The University of Manchester, Manchester M13 9PL, UK; State Key Laboratory of Biochemical Engineering, Institute of Process Engineering, Chinese Academy of Sciences, Beijing 100190, PR China
| | - Xuzhi Hu
- Biological Physics Laboratory, Department of Physics and Astronomy, Faculty of Science and Engineering, The University of Manchester, Manchester M13 9PL, UK
| | - Lin Zhang
- Biological Physics Laboratory, Department of Physics and Astronomy, Faculty of Science and Engineering, The University of Manchester, Manchester M13 9PL, UK
| | - Ke Fa
- Biological Physics Laboratory, Department of Physics and Astronomy, Faculty of Science and Engineering, The University of Manchester, Manchester M13 9PL, UK
| | - Mingrui Liao
- Biological Physics Laboratory, Department of Physics and Astronomy, Faculty of Science and Engineering, The University of Manchester, Manchester M13 9PL, UK
| | - Huayang Liu
- Biological Physics Laboratory, Department of Physics and Astronomy, Faculty of Science and Engineering, The University of Manchester, Manchester M13 9PL, UK
| | | | - Mario Campana
- ISIS Pulsed Neutron & Muon Source, STFC Rutherford Appleton Laboratory, Didcot OX11 0QX, UK
| | - Jian Ren Lu
- Biological Physics Laboratory, Department of Physics and Astronomy, Faculty of Science and Engineering, The University of Manchester, Manchester M13 9PL, UK.
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Fa K, Liu H, Li Z, Gong H, Petkov J, Ren Lu J. Acyl Chain Length Tuning Improves Antimicrobial Potency and Biocompatibility of Short Designed Lipopeptides. J Colloid Interface Sci 2022; 630:911-923. [DOI: 10.1016/j.jcis.2022.10.114] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/06/2022] [Revised: 10/16/2022] [Accepted: 10/22/2022] [Indexed: 11/06/2022]
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Fa K, Liu H, Gong H, Zhang L, Liao M, Hu X, Ciumac D, Li P, Webster J, Petkov J, Thomas RK, Lu JR. In-Membrane Nanostructuring of Cationic Amphiphiles Affects Their Antimicrobial Efficacy and Cytotoxicity: A Comparison Study between a De Novo Antimicrobial Lipopeptide and Traditional Biocides. Langmuir 2022; 38:6623-6637. [PMID: 35587380 PMCID: PMC9161444 DOI: 10.1021/acs.langmuir.2c00506] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 03/01/2022] [Revised: 05/06/2022] [Indexed: 06/15/2023]
Abstract
Cationic biocides have been widely used as active ingredients in personal care and healthcare products for infection control and wound treatment for a long time, but there are concerns over their cytotoxicity and antimicrobial resistance. Designed lipopeptides are potential candidates for alleviating these issues because of their mildness to mammalian host cells and their high efficacy against pathogenic microbial membranes. In this study, antimicrobial and cytotoxic properties of a de novo designed lipopeptide, CH3(CH2)12CO-Lys-Lys-Gly-Gly-Ile-Ile-NH2 (C14KKGGII), were assessed against that of two traditional cationic biocides CnTAB (n = 12 and 14), with different critical aggregation concentrations (CACs). C14KKGGII was shown to be more potent against both bacteria and fungi but milder to fibroblast host cells than the two biocides. Biophysical measurements mimicking the main features of microbial and host cell membranes were obtained for both lipid monolayer models using neutron reflection and small unilamellar vesicles (SUVs) using fluorescein leakage and zeta potential changes. The results revealed selective binding to anionic lipid membranes from the lipopeptide and in-membrane nanostructuring that is distinctly different from the co-assembly of the conventional CnTAB. Furthermore, CnTAB binding to the model membranes showed low selectivity, and its high cytotoxicity could be attributed to both membrane lysis and chemical toxicity. This work demonstrates the advantages of the lipopeptides and their potential for further development toward clinical application.
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Affiliation(s)
- Ke Fa
- Biological
Physics Laboratory, School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, U.K.
| | - Huayang Liu
- Biological
Physics Laboratory, School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, U.K.
| | - Haoning Gong
- Biological
Physics Laboratory, School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, U.K.
| | - Lin Zhang
- Biological
Physics Laboratory, School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, U.K.
| | - Mingrui Liao
- Biological
Physics Laboratory, School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, U.K.
| | - Xuzhi Hu
- Biological
Physics Laboratory, School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, U.K.
| | - Daniela Ciumac
- Biological
Physics Laboratory, School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, U.K.
| | - Peixun Li
- ISIS
Neutron Facility, Rutherford Appleton Laboratory,
STFC, Chilton, Didcot, Oxon OX11 0QX, U.K.
| | - John Webster
- ISIS
Neutron Facility, Rutherford Appleton Laboratory,
STFC, Chilton, Didcot, Oxon OX11 0QX, U.K.
| | - Jordan Petkov
- Arc
UK Biocides Ltd, Arxada,
Hexagon Tower, Delaunays Road, Blackley, Manchester M9 8ZS, U.K.
| | - Robert K. Thomas
- Physical
and Theoretical Chemistry, University of
Oxford, South Parks, Oxford OX1
3QZ, U.K.
| | - Jian Ren Lu
- Biological
Physics Laboratory, School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, U.K.
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Liu H, Fa K, Hu X, Li Z, Zhang L, Ma K, Fragneto G, Li P, Webster JRP, Petkov JT, Thomas RK, Ren Lu J. Structural features of interfacially adsorbed acyl-l-carnitines. J Colloid Interface Sci 2022; 623:368-377. [PMID: 35594595 DOI: 10.1016/j.jcis.2022.05.024] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2022] [Revised: 05/02/2022] [Accepted: 05/04/2022] [Indexed: 11/19/2022]
Abstract
HYPOTHESIS Acyl-l-carnitines (CnLCs) are potentially important as biosurfactants in drug delivery and tissue engineering due to their good biocompatibility. However, little is currently known about the basic interfacial behavior underlying their technological applications. Following our previous characterization of their solution aggregation and adsorption at the air/water interface, this work examines how they adsorb at the hydrophilic solid/liquid interface. EXPERIMENTS As the SiO2/water interface has served as the model substrate for many interfacial adsorption studies, so it has been used in this work as the solid substrate to facilitate dynamic adsorption by spectroscopic ellipsometry (SE) and structural determination of the adsorbed layers by neutron reflection (NR) under different conditions at the SiO2/water interface from a group of CnLC (n = 12, 14, and 16). FINDINGS CnLC surfactants are zwitterionic at neutral pH. They reached saturated adsorption above their critical micellar concentrations (CMCs) and formed a sandwich bilayer with a head-tail-head structure at the hydrophilic SiO2/water interface. The total thicknesses of the adsorbed layers at CMC were found to be 33 ± 2, 35 ± 2, and 37 ± 2 Å for C12LC, C14LC, and C16LC, respectively, with their inner and outer head layers remaining similar but the thickness of the interdigitated middle layer increasing with acyl chain length. As the solution becomes acidic, the carboxyl groups become protonated and the l-carnitine heads are net positively charged, resulting in increased repulsion between the head groups. In this situation, the CnLC surfactants are adsorbed as distinct aggregates to reduce repulsive interaction, resulting in reduced surfactant volume fraction and layer thickness. However, a high ionic strength can screen the repulsive interaction and enhance the adsorbed amount, effectively diminishing the impact of pH. This information provides a useful basis for exploring the technological applications of CnLCs involving a solid substrate.
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Affiliation(s)
- Huayang Liu
- Biological Physics Laboratory, School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK
| | - Ke Fa
- Biological Physics Laboratory, School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK
| | - Xuzhi Hu
- Biological Physics Laboratory, School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK
| | - Zongyi Li
- Biological Physics Laboratory, School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK
| | - Lin Zhang
- Biological Physics Laboratory, School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK
| | - Kun Ma
- ISIS Neutron Facility, Rutherford Appleton Laboratory, STFC, Chilton, Didcot, Oxon OX11 0QX, UK
| | - Giovanna Fragneto
- Institut Laue-Langevin, 71 Avenue des Martyrs, CS20156, 38042 Grenoble Cedex 9, France
| | - Peixun Li
- ISIS Neutron Facility, Rutherford Appleton Laboratory, STFC, Chilton, Didcot, Oxon OX11 0QX, UK
| | - John R P Webster
- ISIS Neutron Facility, Rutherford Appleton Laboratory, STFC, Chilton, Didcot, Oxon OX11 0QX, UK
| | - Jordan T Petkov
- Arxada, Hexagon Tower, Delaunays Road, Blackley, Manchester M9 8ZS, UK
| | - Robert K Thomas
- Physical and Theoretical Chemistry, University of Oxford, South Parks, Oxford OX1 3QZ, UK
| | - Jian Ren Lu
- Biological Physics Laboratory, School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK.
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Liu H, Fa K, Hu X, Li Z, Ma K, Liao M, Zhang L, Schweins R, Maestro A, Li P, Webster JRP, Petkov J, Thomas RK, Lu JR. How do chain lengths of acyl-l-carnitines affect their surface adsorption and solution aggregation? J Colloid Interface Sci 2021; 609:491-502. [PMID: 34863541 DOI: 10.1016/j.jcis.2021.11.056] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2021] [Revised: 11/10/2021] [Accepted: 11/11/2021] [Indexed: 11/26/2022]
Abstract
HYPOTHESIS l-carnitines in our body systems can be readily converted into acyl-l-carnitines which have a prominent place in cellular energy generation by supporting the transport of long-chain fatty acids into mitochondria. As biocompatible surfactants, acyl-l-carnitines have potential to be useful in technical, personal care and healthcare applications. However, the lack of understanding of the effects of their molecular structures on their physical properties has constrained their potential use. EXPERIMENTS This work reports the study of the influence of the acyl chain lengths of acyl-l-carnitines (CnLC) on solubility, surface adsorption and aggregation. Critical micellar concentrations (CMCs) of CnLC were determined by surface tension measurements. Neutron reflection (NR) was used to further examine the structure and composition of the adsorbed CnLC layer. The structural changes of the micellar aggregates under different concentrations of CnLC, pH and ionic strength were determined by dynamic light scattering (DLS) and small angle neutron scattering (SANS). FINDINGS C12LC is fully soluble over a wide temperature and concentration range. There is however a strong decline of solubility with increasing acyl chain length. The adsorption and aggregation behavior of C14LC was therefore studied at 30 °C and C16LC at 45 °C. The solubility boundaries displayed distinct hysteresis with respect to heating and cooling. The CMCs of C12LC, C14LC and C16LC at pH 7 were 1.1 ± 0.1, 0.10 ± 0.02 and 0.010 ± 0.005 mM, respectively, with the limiting values of the area per molecule at the CMC being 45.4 ± 2, 47.5 ± 2 and 48.8 ± 2 Å2 and the thicknesses of the adsorbed CnLC layers at the air/water interface increasing from 21.5 ± 2 to 22.6 ± 2 to 24.2 ± 2 Å, respectively. All three surfactants formed core-shell spherical micelles with comparable dimensional parameters apart from an increase in core radius with acyl chain length. This study outlines the effects of acyl chain length on the physicochemical properties of CnLCs under different environmental conditions, serving as a useful basis for developing their potential applications.
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Affiliation(s)
- Huayang Liu
- Biological Physics Laboratory, Department of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK
| | - Ke Fa
- Biological Physics Laboratory, Department of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK
| | - Xuzhi Hu
- Biological Physics Laboratory, Department of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK
| | - Zongyi Li
- Biological Physics Laboratory, Department of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK
| | - Kun Ma
- ISIS Neutron Facility, Rutherford Appleton Laboratory, STFC, Chilton, Didcot, Oxon OX11 0QX, UK
| | - Mingrui Liao
- Biological Physics Laboratory, Department of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK
| | - Lin Zhang
- Biological Physics Laboratory, Department of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK
| | - Ralf Schweins
- Institut Laue-Langevin, 71 Avenue des Martyrs, CS20156, 38042 Grenoble Cedex 9, France
| | - Armando Maestro
- Institut Laue-Langevin, 71 Avenue des Martyrs, CS20156, 38042 Grenoble Cedex 9, France
| | - Peixun Li
- ISIS Neutron Facility, Rutherford Appleton Laboratory, STFC, Chilton, Didcot, Oxon OX11 0QX, UK
| | - John R P Webster
- ISIS Neutron Facility, Rutherford Appleton Laboratory, STFC, Chilton, Didcot, Oxon OX11 0QX, UK
| | - Jordan Petkov
- Biological Physics Laboratory, Department of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK; Arxada, Hexagon Tower, Delaunays Road, Blackley, Manchester M9 8ZS, UK.
| | - Robert K Thomas
- Physical and Theoretical Chemistry, University of Oxford, South Parks, Oxford OX1 3QZ, UK
| | - Jian Ren Lu
- Biological Physics Laboratory, Department of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK.
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Gong H, Hu X, Liao M, Fa K, Ciumac D, Clifton LA, Sani MA, King SM, Maestro A, Separovic F, Waigh TA, Xu H, McBain AJ, Lu JR. Structural Disruptions of the Outer Membranes of Gram-Negative Bacteria by Rationally Designed Amphiphilic Antimicrobial Peptides. ACS Appl Mater Interfaces 2021; 13:16062-16074. [PMID: 33797891 DOI: 10.1021/acsami.1c01643] [Citation(s) in RCA: 33] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Gram-negative bacteria are covered by both an inner cytoplasmic membrane (IM) and an outer membrane (OM). Antimicrobial peptides (AMPs) must first permeate through the OM and cell wall before attacking the IM to cause cytoplasmic leakage and kill the bacteria. The bacterial OM is an asymmetric bilayer with the outer leaflet primarily composed of lipopolysaccharides (LPSs) and the inner leaflet composed of phospholipids (PLs). Two cationic α-helical AMPs were designed to target Gram-negative bacteria, a full peptide G(IIKK)3I-NH2 (G3), and a hydrophobic lipopeptide C8-G(IIKK)2I-NH2 (C8G2, with C8 denoting the octanoyl chain). LPS dominates OM functions as the first line of defense against antibiotics, thereby reducing drug susceptibility. This work explores how the two AMPs interact with LPS through several carefully chosen OM models that facilitated measurements from solid-state nuclear magnetic resonance (ss-NMR), small-angle neutron scattering (SANS), and neutron reflectivity (NR). The results revealed that G3 molecules bound preferably to the LPS head region and functioned as bridge molecules to reassemble the dislocated lipids into bilayer stacks. In contrast, C8G2 lipopeptides could quickly penetrate into the central region of the OM to cause direct removal of some membrane lipids. Different structural disruptions implicated different antimicrobial efficacies from these AMPs. The demonstration of the structural features underlying different susceptibilities of the OM to AMPs offers a useful route for the future development of strain-specific AMPs against antimicrobial-resistant pathogens.
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Affiliation(s)
- Haoning Gong
- Biological Physics Laboratory, Department of Physics and Astronomy, Faculty of Science and Engineering, The University of Manchester, Oxford Road, Manchester M13 9PL, UK
- Division of Pharmacy and Optometry, Faculty of Biology, Medicine and Health, The University of Manchester, Oxford Road, Manchester M13 9PL, UK
| | - Xuzhi Hu
- Biological Physics Laboratory, Department of Physics and Astronomy, Faculty of Science and Engineering, The University of Manchester, Oxford Road, Manchester M13 9PL, UK
| | - Mingrui Liao
- Biological Physics Laboratory, Department of Physics and Astronomy, Faculty of Science and Engineering, The University of Manchester, Oxford Road, Manchester M13 9PL, UK
- Division of Pharmacy and Optometry, Faculty of Biology, Medicine and Health, The University of Manchester, Oxford Road, Manchester M13 9PL, UK
| | - Ke Fa
- Biological Physics Laboratory, Department of Physics and Astronomy, Faculty of Science and Engineering, The University of Manchester, Oxford Road, Manchester M13 9PL, UK
| | - Daniela Ciumac
- Biological Physics Laboratory, Department of Physics and Astronomy, Faculty of Science and Engineering, The University of Manchester, Oxford Road, Manchester M13 9PL, UK
| | - Luke A Clifton
- ISIS Pulsed Neutron & Muon Source, STFC Rutherford Appleton Laboratory, Harwell Campus, Didcot OX11 0QX, UK
| | - Marc-Antoine Sani
- School of Chemistry, Bio21 Institute, University of Melbourne, Melbourne, VIC 3010, Australia
| | - Stephen M King
- ISIS Pulsed Neutron & Muon Source, STFC Rutherford Appleton Laboratory, Harwell Campus, Didcot OX11 0QX, UK
| | - Armando Maestro
- Institute Laue Langevin, 71 Avenue des Martyrs, CS-20156, 38042 Grenoble, France
| | - Frances Separovic
- School of Chemistry, Bio21 Institute, University of Melbourne, Melbourne, VIC 3010, Australia
| | - Thomas A Waigh
- Biological Physics Laboratory, Department of Physics and Astronomy, Faculty of Science and Engineering, The University of Manchester, Oxford Road, Manchester M13 9PL, UK
| | - Hai Xu
- State Key Laboratory of Heavy Oil Processing and the Centre for Bioengineering and Biotechnology, China University of Petroleum (East China), 66 Changjiang West Road, Qingdao 266580, China
| | - Andrew J McBain
- Division of Pharmacy and Optometry, Faculty of Biology, Medicine and Health, The University of Manchester, Oxford Road, Manchester M13 9PL, UK
| | - Jian Ren Lu
- Biological Physics Laboratory, Department of Physics and Astronomy, Faculty of Science and Engineering, The University of Manchester, Oxford Road, Manchester M13 9PL, UK
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Liu H, Hu X, Li Z, Fa K, Gong H, Ma K, Liao M, Li P, Webster JRP, Petkov JT, Thomas RK, Ren Lu J. Surface adsorption and solution aggregation of a novel lauroyl-l-carnitine surfactant. J Colloid Interface Sci 2021; 591:106-114. [PMID: 33592522 DOI: 10.1016/j.jcis.2021.01.106] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2020] [Revised: 01/18/2021] [Accepted: 01/31/2021] [Indexed: 11/19/2022]
Abstract
HYPOTHESIS l-carnitine plays a crucial role in the cellular production of energy by transporting fatty acids into mitochondria. Acylated l-carnitines are amphiphilic and if appropriate physical properties were demonstrated, they could replace many currently used surfactants with improved biocompatibility and health benefits. EXPERIMENTS This work evaluated the surface adsorption of lauroyl-l-carnitine (C12LC) and its aggregation behavior. The size and shape of the aggregates of C12LC surfactant were studied at different temperatures, concentrations, pH and ionic strength by dynamic light scattering (DLS) and small-angle neutron scattering (SANS). Surface tension measurements were carried out to determine the critical micellar concentration (CMC) of C12LC. Combining with the Gibbs equation, the surface excess at different concentrations could be determined. Neutron reflection (NR) was used to determine the structure of the adsorbed layer at the air/water interface with the help of isotopic contrast variations. FINDINGS At pH 7, the limiting area per molecule (ACMC) of the zwitterionic C12LC adsorbed layer at the air/water interface was found to be 46 Å2 from surface tension and neutron reflection, smaller than the values of C12PC, C12E5, DTAB, C12C4betaine and C12C8betaine but close to that of SDS. A pronounced surface tension minimum at pH 2 at the low ionic strength was linked to a minimum value of area per molecule of about 30 Å2, indicating the competitive adsorption from traces of lauric acid produced by hydrolysis of C12LC. As the concentration increased, area per molecule reached a plateau of 37-39 Å2, indicating the dissolution of the more surface-active lauric acid into the micelles of C12LC. DLS and SANS showed that the size and shape of micelles had little response to temperature, concentration, ionic strength or pH. The SANS profiles measured under 3 isotopic contrasts could be well fitted by the core-shell model, giving a spherical core radius of 15.7 Å and a shell thickness of 10.5 Å. The decrease of pH led to more protonated carboxyl groups and more positively charged micelles, but the micellar structures remained unchanged, in spite of their stronger interaction. These features make C12LC potentially attractive as a solubilizing agent.
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Affiliation(s)
- Huayang Liu
- Biological Physics Laboratory, School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK
| | - Xuzhi Hu
- Biological Physics Laboratory, School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK
| | - Zongyi Li
- Biological Physics Laboratory, School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK
| | - Ke Fa
- Biological Physics Laboratory, School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK
| | - Haoning Gong
- Biological Physics Laboratory, School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK
| | - Kun Ma
- ISIS Neutron Facility, Rutherford Appleton Laboratory, STFC, Chilton, Didcot, Oxon OX11 0QX, UK
| | - Mingrui Liao
- Biological Physics Laboratory, School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK
| | - Peixun Li
- ISIS Neutron Facility, Rutherford Appleton Laboratory, STFC, Chilton, Didcot, Oxon OX11 0QX, UK
| | - John R P Webster
- ISIS Neutron Facility, Rutherford Appleton Laboratory, STFC, Chilton, Didcot, Oxon OX11 0QX, UK
| | - Jordan T Petkov
- Arch UK Biocides Ltd, Lonza, Hexagon Tower, Delaunays Road, Blackley, Manchester M9 8ZS, UK
| | - Robert K Thomas
- Physical and Theoretical Chemistry, University of Oxford, South Parks, Oxford OX1 3QZ, UK
| | - Jian Ren Lu
- Biological Physics Laboratory, School of Physics and Astronomy, University of Manchester, Oxford Road, Manchester M13 9PL, UK.
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Gong H, Sani MA, Hu X, Fa K, Hart JW, Liao M, Hollowell P, Carter J, Clifton LA, Campana M, Li P, King SM, Webster JRP, Maestro A, Zhu S, Separovic F, Waigh TA, Xu H, McBain AJ, Lu JR. How do Self-Assembling Antimicrobial Lipopeptides Kill Bacteria? ACS Appl Mater Interfaces 2020; 12:55675-55687. [PMID: 33259204 DOI: 10.1021/acsami.0c17222] [Citation(s) in RCA: 28] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
Antimicrobial peptides are promising alternatives to traditional antibiotics. A group of self-assembling lipopeptides was formed by attaching an acyl chain to the N-terminus of α-helix-forming peptides with the sequence Cx-G(IIKK)yI-NH2 (CxGy, x = 4-12 and y = 2). CxGy self-assemble into nanofibers above their critical aggregation concentrations (CACs). With increasing x, the CACs decrease and the hydrophobic interactions increase, promoting secondary structure transitions within the nanofibers. Antimicrobial activity, determined by the minimum inhibition concentration (MIC), also decreases with increasing x, but the MICs are significantly smaller than the CACs, suggesting effective bacterial membrane-disrupting power. Unlike conventional antibiotics, both C8G2 and C12G2 can kill Staphylococcus aureus and Escherichia coli after only minutes of exposure under the concentrations studied. C12G2 nanofibers have considerably faster killing dynamics and lower cytotoxicity than their nonaggregated monomers. Antimicrobial activity of peptide aggregates has, to date, been underexploited, and it is found to be a very promising mechanism for peptide design. Detailed evidence for the molecular mechanisms involved is provided, based on superresolution fluorescence microscopy, solid-state nuclear magnetic resonance, atomic force microscopy, neutron scattering/reflectivity, circular dichroism, and Brewster angle microscopy.
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Affiliation(s)
- Haoning Gong
- Biological Physics Laboratory, Department of Physics and Astronomy, Faculty of Science and Engineering, The University of Manchester, Oxford Road, Manchester M13 9PL, U.K
- Division of Pharmacy and Optometry, Faculty of Biology, Medicine and Health, The University of Manchester, Oxford Road, Manchester M13 9PL, U.K
| | - Marc-Antoine Sani
- School of Chemistry, Bio21 Institute, University of Melbourne, Melbourne, Victoria 3010, Australia
| | - Xuzhi Hu
- Biological Physics Laboratory, Department of Physics and Astronomy, Faculty of Science and Engineering, The University of Manchester, Oxford Road, Manchester M13 9PL, U.K
| | - Ke Fa
- Biological Physics Laboratory, Department of Physics and Astronomy, Faculty of Science and Engineering, The University of Manchester, Oxford Road, Manchester M13 9PL, U.K
| | - Jack William Hart
- Biological Physics Laboratory, Department of Physics and Astronomy, Faculty of Science and Engineering, The University of Manchester, Oxford Road, Manchester M13 9PL, U.K
- Photon Science Institute, The University of Manchester, Oxford Road, Manchester M13 9PL, U.K
| | - Mingrui Liao
- Biological Physics Laboratory, Department of Physics and Astronomy, Faculty of Science and Engineering, The University of Manchester, Oxford Road, Manchester M13 9PL, U.K
- Division of Pharmacy and Optometry, Faculty of Biology, Medicine and Health, The University of Manchester, Oxford Road, Manchester M13 9PL, U.K
| | - Peter Hollowell
- Biological Physics Laboratory, Department of Physics and Astronomy, Faculty of Science and Engineering, The University of Manchester, Oxford Road, Manchester M13 9PL, U.K
| | - Jessica Carter
- Biological Physics Laboratory, Department of Physics and Astronomy, Faculty of Science and Engineering, The University of Manchester, Oxford Road, Manchester M13 9PL, U.K
| | - Luke A Clifton
- ISIS Pulsed Neutron & Muon Source, STFC Rutherford Appleton Laboratory, Harwell Campus, Didcot OX11 0QX, U.K
| | - Mario Campana
- ISIS Pulsed Neutron & Muon Source, STFC Rutherford Appleton Laboratory, Harwell Campus, Didcot OX11 0QX, U.K
| | - Peixun Li
- ISIS Pulsed Neutron & Muon Source, STFC Rutherford Appleton Laboratory, Harwell Campus, Didcot OX11 0QX, U.K
| | - Stephen M King
- ISIS Pulsed Neutron & Muon Source, STFC Rutherford Appleton Laboratory, Harwell Campus, Didcot OX11 0QX, U.K
| | - John R P Webster
- ISIS Pulsed Neutron & Muon Source, STFC Rutherford Appleton Laboratory, Harwell Campus, Didcot OX11 0QX, U.K
| | - Armando Maestro
- Institute Laue Langevin, 71 Avenue des Martyrs, CS-20156, Grenoble 38042, France
| | - Shiying Zhu
- School of Chemistry, Bio21 Institute, University of Melbourne, Melbourne, Victoria 3010, Australia
| | - Frances Separovic
- School of Chemistry, Bio21 Institute, University of Melbourne, Melbourne, Victoria 3010, Australia
| | - Thomas A Waigh
- Biological Physics Laboratory, Department of Physics and Astronomy, Faculty of Science and Engineering, The University of Manchester, Oxford Road, Manchester M13 9PL, U.K
- Photon Science Institute, The University of Manchester, Oxford Road, Manchester M13 9PL, U.K
| | - Hai Xu
- State Key Laboratory of Heavy Oil Processing and the Centre for Bioengineering and Biotechnology, China University of Petroleum (East China), 66 Changjiang West Road, Qingdao 266580, China
| | - Andrew J McBain
- Division of Pharmacy and Optometry, Faculty of Biology, Medicine and Health, The University of Manchester, Oxford Road, Manchester M13 9PL, U.K
| | - Jian Ren Lu
- Biological Physics Laboratory, Department of Physics and Astronomy, Faculty of Science and Engineering, The University of Manchester, Oxford Road, Manchester M13 9PL, U.K
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9
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Gong H, Liao M, Hu X, Fa K, Phanphak S, Ciumac D, Hollowell P, Shen K, Clifton LA, Campana M, Webster JRP, Fragneto G, Waigh TA, McBain AJ, Lu JR. Aggregated Amphiphilic Antimicrobial Peptides Embedded in Bacterial Membranes. ACS Appl Mater Interfaces 2020; 12:44420-44432. [PMID: 32909733 DOI: 10.1021/acsami.0c09931] [Citation(s) in RCA: 27] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Molecular dynamics (MD) simulations, stochastic optical reconstruction microscopy (STORM), and neutron reflection (NR) were combined to explore how antimicrobial peptides (AMPs) can be designed to promote the formation of nanoaggregates in bacterial membranes and impose effective bactericidal actions. Changes in the hydrophobicity of the designed AMPs were found to have a strong influence on their bactericidal potency and cytotoxicity. G(IIKK)3I-NH2 (G3) achieved low minimum inhibition concentrations (MICs) and effective dynamic kills against both antibiotic-resistant and -susceptible bacteria. However, a G3 derivative with weaker hydrophobicity, KI(KKII)2I-NH2 (KI), exhibited considerably lower membrane-lytic activity. In contrast, the more hydrophobic G(ILKK)3L-NH2 (GL) peptide achieved MICs similar to those observed for G3 but with worsened hemolysis. Both the model membranes studied by Brewster angle microscopy, zeta potential measurements, and NR and the real bacterial membranes examined with direct STORM contained membrane-inserted peptide aggregates upon AMP exposure. These structural features were well supported by MD simulations. By revealing how AMPs self-assemble in microbial membranes, this work provides important insights into AMP mechanistic actions and allows further fine-tuning of antimicrobial potency and cytotoxicity.
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Affiliation(s)
- Haoning Gong
- Biological Physics Laboratory, Department of Physics and Astronomy, Faculty of Science and Engineering, The University of Manchester, Oxford Road, Manchester M13 9PL, U.K
- Division of Pharmacy and Optometry, Faculty of Biology, Medicine and Health, The University of Manchester, Oxford Road, Manchester M13 9PL, U.K
| | - Mingrui Liao
- Biological Physics Laboratory, Department of Physics and Astronomy, Faculty of Science and Engineering, The University of Manchester, Oxford Road, Manchester M13 9PL, U.K
- Division of Pharmacy and Optometry, Faculty of Biology, Medicine and Health, The University of Manchester, Oxford Road, Manchester M13 9PL, U.K
| | - Xuzhi Hu
- Biological Physics Laboratory, Department of Physics and Astronomy, Faculty of Science and Engineering, The University of Manchester, Oxford Road, Manchester M13 9PL, U.K
| | - Ke Fa
- Biological Physics Laboratory, Department of Physics and Astronomy, Faculty of Science and Engineering, The University of Manchester, Oxford Road, Manchester M13 9PL, U.K
| | - Sorasak Phanphak
- Biological Physics Laboratory, Department of Physics and Astronomy, Faculty of Science and Engineering, The University of Manchester, Oxford Road, Manchester M13 9PL, U.K
| | - Daniela Ciumac
- Biological Physics Laboratory, Department of Physics and Astronomy, Faculty of Science and Engineering, The University of Manchester, Oxford Road, Manchester M13 9PL, U.K
| | - Peter Hollowell
- Biological Physics Laboratory, Department of Physics and Astronomy, Faculty of Science and Engineering, The University of Manchester, Oxford Road, Manchester M13 9PL, U.K
| | - Kangcheng Shen
- Biological Physics Laboratory, Department of Physics and Astronomy, Faculty of Science and Engineering, The University of Manchester, Oxford Road, Manchester M13 9PL, U.K
| | - Luke A Clifton
- STFC ISIS Facility, Rutherford Appleton Laboratory, Didcot OX11 0QX, U.K
| | - Mario Campana
- STFC ISIS Facility, Rutherford Appleton Laboratory, Didcot OX11 0QX, U.K
| | - John R P Webster
- STFC ISIS Facility, Rutherford Appleton Laboratory, Didcot OX11 0QX, U.K
| | - Giovanna Fragneto
- Institute of Laue Langevin, 71 Avenue des Martyrs, CS-20156, Grenoble 38042, France
| | - Thomas A Waigh
- Biological Physics Laboratory, Department of Physics and Astronomy, Faculty of Science and Engineering, The University of Manchester, Oxford Road, Manchester M13 9PL, U.K
| | - Andrew J McBain
- Division of Pharmacy and Optometry, Faculty of Biology, Medicine and Health, The University of Manchester, Oxford Road, Manchester M13 9PL, U.K
| | - Jian Ren Lu
- Biological Physics Laboratory, Department of Physics and Astronomy, Faculty of Science and Engineering, The University of Manchester, Oxford Road, Manchester M13 9PL, U.K
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10
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Gong H, Zhang J, Hu X, Li Z, Fa K, Liu H, Waigh TA, McBain A, Lu JR. Hydrophobic Control of the Bioactivity and Cytotoxicity of de Novo-Designed Antimicrobial Peptides. ACS Appl Mater Interfaces 2019; 11:34609-34620. [PMID: 31448889 DOI: 10.1021/acsami.9b10028] [Citation(s) in RCA: 53] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Antimicrobial peptides (AMPs) can target bacterial membranes and kill bacteria through membrane structural damage and cytoplasmic leakage. A group of surfactant-like cationic AMPs was developed from substitutions to selective amino acids in the general formula of G(IIKK)3I-NH2, (called G3, a de novo AMP), to explore the correlation between AMP hydrophobicity and bioactivity. A threshold surface pressure over 12 mN/m was required to cause measurable antimicrobial activity and this corresponded to a critical AMP concentration. Greater surface activity exhibited stronger antimicrobial activity but had the drawback of worsening hemolytic activity. Small unilamellar vesicles (SUVs) with specific lipid compositions were used to model bacterial and host mammalian cell membranes by mimicking the main structural determinants of the charge and composition. Leakage from the SUVs of encapsulated carboxyfluorescein measured by fluorescence spectroscopy indicated a negative correlation between hydrophobicity and model membrane selectivity, consistent with measurements of the zeta potential that demonstrated the extent of AMP binding onto model SUV lipid bilayers. Experiments with model lipid membranes thus explained the trend of minimum inhibitory concentrations and selectivity measured from real cell systems and demonstrated the dominant influence of hydrophobicity. This work provides useful guidance for the improvement of the potency of AMPs via structural design, whilst taking due consideration of cytotoxicity.
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11
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Kumar AM, Fa K, Vankawala R, Vora M, Kode RK, Pankewycz OG, Lattavi MR, Fyfe B, Damask AM, Ferry E, Stabler S, Tomeny MB, Phillips K, Lingaraju R, Kumar MS. Simulect, calcineurin inhibitor, mycophenolate mofetil, and prednisone is more effective than OKT3, calcineurin inhibitor, hycophendate mofetil, and prednisone in African American kidney recipients in reducing acute rejections and prolonging graft survival. Transplant Proc 2001; 33:3195-6. [PMID: 11750370 DOI: 10.1016/s0041-1345(01)02359-4] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
Affiliation(s)
- A M Kumar
- Department of Transplantation, MCP Hahnemann University, Philadelphia, Pennsylvania 19102, USA
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