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Gupta T, Mondal AK, Pani I, Chattopadhyay K, Pal SK. Elucidating liquid crystal-aqueous interface for the study of cholesterol-mediated action of a β-barrel pore forming toxin. SOFT MATTER 2022; 18:5293-5301. [PMID: 35790122 DOI: 10.1039/d2sm00447j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/15/2023]
Abstract
Pore-forming toxins (PFTs) produced by pathogenic bacteria serve as prominent virulence factors with potent cell-killing activity. Most of the β-barrel PFTs form transmembrane oligomeric pores in the membrane lipid bilayer in the presence of cholesterol. The pore-formation mechanisms of the PFTs highlight well-orchestrated regulated events in the membrane environment, which involve dramatic changes in the protein structure and organization. Also, concerted crosstalk between protein and membrane lipid components appears to play crucial roles in the process. Membrane-damaging lesions formed by the pore assembly of the PFTs would also be expected to impose drastic alterations in the membrane organization, details of which remain obscure in most of the cases. Prior reports have established that aqueous interfaces of liquid crystals (LCs) offer promise as responsive interfaces for biomolecular events (at physiologically relevant concentrations), which can be visualized as optical signals. Inspired by this, herein, we sought to understand the lipid membrane interactions of a β-barrel PFT i.e., Vibrio cholerae cytolysin (VCC), using LC-aqueous interfaces. Our results show the formation of dendritic patterns upon the addition of VCC to the lipid embedded with cholesterol over the LC film. In contrast, we did not observe any LC reorientation upon the addition of VCC to the lipid-laden LC-aqueous interface in the absence of cholesterol. An array of techniques such as polarizing optical microscopy (POM), atomic force microscopy (AFM), and fluorescence measurements were utilized to decipher the LC response to the lipid interactions of VCC occurring at these interfaces. Altogether, the results obtained from our study provide a novel platform to explore the mechanistic aspects of the protein-membrane interactions, in the process of membrane pore-formation by the membrane-damaging PFTs.
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Affiliation(s)
- Tarang Gupta
- Department of Chemical Sciences, Indian Institute of Science Education and Research Mohali, Knowledge City, Sector-81, SAS Nagar, Mohali 140306, India.
| | - Anish Kumar Mondal
- Department of Biological Sciences, Indian Institute of Science Education and Research Mohali, Knowledge City, Sector-81, SAS Nagar, Mohali 140306, India.
| | - Ipsita Pani
- Department of Chemical Sciences, Indian Institute of Science Education and Research Mohali, Knowledge City, Sector-81, SAS Nagar, Mohali 140306, India.
| | - Kausik Chattopadhyay
- Department of Biological Sciences, Indian Institute of Science Education and Research Mohali, Knowledge City, Sector-81, SAS Nagar, Mohali 140306, India.
| | - Santanu Kumar Pal
- Department of Chemical Sciences, Indian Institute of Science Education and Research Mohali, Knowledge City, Sector-81, SAS Nagar, Mohali 140306, India.
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Abstract
Phase transitions in materials are accompanied by drastic changes in their properties. Systems abruptly become softer, more conductive, have better heat storage, or support chemical reactions more efficiently. Since changes take place over small variations in external conditions (tension, temperature, pH, calcium), they appear like an on/off switch. Here, we provide experimental evidence that membrane patches of single living cells can go through a reversible phase transition. It is extremely “sharp” (highly nonlinear), and from a thermodynamic point of view we conclude it cannot only be triggered by temperature but also by pH changes (as produced by enzymes). The results strongly support the idea that phase transitions may be a tool for living systems to control their functions even specifically. The origin of nonlinear responses in cells has been suggested to be crucial for various cell functions including the propagation of the nervous impulse. In physics, nonlinear behavior often originates from phase transitions. Evidence for such transitions on the single-cell level, however, has so far not been provided, leaving the field unattended by the biological community. Here, we demonstrate that single cells of a human neuronal cell line display all optical features of a sharp, highly nonlinear phase transition within their membrane. The transition is reversible and does not originate from protein denaturation. Triggered by temperature and modified by pH here, a thermodynamic approach strongly suggests that similar nonlinear state changes can be induced by other variables such as calcium or mechanical stress. At least in lipid membranes, such state changes are accompanied by significant changes in permeability, enzyme activity, elastic, and electrical properties.
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Shrivastava S. Shock and detonation waves at an interface and the collision of action potentials. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2021; 162:111-121. [PMID: 33516823 DOI: 10.1016/j.pbiomolbio.2020.12.002] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/14/2020] [Revised: 11/24/2020] [Accepted: 12/13/2020] [Indexed: 10/22/2022]
Abstract
Action potentials in neurons are known to annihilate each other upon collision, while there are cases where they might penetrate each other. The fate of two waves upon collision is critically dependent on the underlying mechanism of propagation and therefore an understanding of possible outcomes of collision under different conditions is important. Previously, compression waves that travel within the plasma membrane of a neuron have been proposed as a thermodynamic basis for the propagation of action potentials. In this context, it was recently shown that two-dimensional compressive shock waves in the model system of lipid monolayers behave strikingly similar to action potentials in neurons and can even annihilate each other upon head-on collision. However, even a qualitative mechanism remained unclear. To this end, we summarise the fundamentals of shock physics as applied to an interface and recap how it explained the observation of threshold and saturation of shockwaves in the lipid monolayer (all - or - none). We then compare the theory with the soliton model that has the same fundamental premise, i.e. the conservation laws and thermodynamics, and was previously proposed as a model for the nerve pulse propagation. We elaborate on how the two approaches make different predictions with regards to collisions and the detailed structure of the wave-front. As a case study and a new qualitative result, we finally show that previously unexplained annihilation of shock waves in the lipid monolayer is a direct consequence of the nature of state changes, i.e. jump conditions, within these shockwaves.
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Single cell electrophysiological alterations under dynamic loading at ultrasonic frequencies. BRAIN MULTIPHYSICS 2021. [DOI: 10.1016/j.brain.2021.100031] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
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Kruglikov I. Acoustic Waves in Axonal Membrane and Caveolins are the New Targets for Pain Treatment with High Frequency Ultrasound. J Pain Res 2020; 13:2791-2798. [PMID: 33173328 PMCID: PMC7646452 DOI: 10.2147/jpr.s281468] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2020] [Accepted: 10/14/2020] [Indexed: 12/18/2022] Open
Abstract
Reciprocal interaction between electrical and mechanical waves observed in axonal membrane during its excitation leads to a paradigm shift in pain research making the uncoupling of electro-mechanical signals an interesting target in pain treatment. This uncoupling can be realized either through direct disturbance of the mechanical surface waves in axonal membrane or through shifting of the thermodynamic state of this membrane far from its phase transition point. Both effects can be effectively realized through application of the very high frequency ultrasound waves. Additional target for application of ultrasound in pain treatment is the caveolin-1, which is abundantly present in Schwann cells as well as in the non-axonal tissues. Both targets demonstrate frequency-dependent reactions, thus making a very high frequency ultrasound a promising treatment modality in pain treatment.
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Affiliation(s)
- Ilja Kruglikov
- Scientific Department, Wellcomet GmbH, Karlsruhe, Germany
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Fabiunke S, Fillafer C, Paeger A, Schneider MF. Optical studies of membrane state during action potential propagation. PROGRESS IN BIOPHYSICS AND MOLECULAR BIOLOGY 2020; 162:69-78. [DOI: 10.1016/j.pbiomolbio.2020.11.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/15/2020] [Revised: 10/05/2020] [Accepted: 11/13/2020] [Indexed: 10/23/2022]
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Browning RJ, Aron M, Booth A, Rademeyer P, Wing S, Brans V, Shrivastava S, Carugo D, Stride E. Spectral Imaging for Microbubble Characterization. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2020; 36:609-617. [PMID: 31855435 DOI: 10.1021/acs.langmuir.9b03828] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Microbubbles stabilized by an outer lipid shell have been studied extensively for both diagnostic and therapeutic applications. The shell composition can significantly influence microbubble behavior, but performing quantitative measurements of shell properties is challenging. The aim of this study is to investigate the use of spectral imaging to characterize the surface properties of a range of microbubble formulations representing both commercial and research agents. A lipophilic dye, C-laurdan, whose fluorescence emission varies according to the properties of the local environment, was used to compare the degree and uniformity of the lipid order in the microbubble shell, and these measurements were compared with the acoustic response and stability of the different formulations. Spectral imaging was found to be suitable for performing rapid and hence relatively high throughput measurements of microbubble surface properties. Interestingly, despite significant differences in lipid molecule size and charge, all of the different formulations exhibited highly ordered lipid shells. Measurements of liposomes with the same composition and the debris generated by destroying lipid microbubbles with ultrasound (US) showed that these exhibited a lower and more varied lipid order than intact microbubbles. This suggests that the high lipid order of microbubbles is due primarily to compression of the shell as a result of surface tension and is only minimally affected by composition. This also explains the similarity in acoustic response observed between the formulations, because microbubble dynamics are determined by the diameter and shell viscoelastic properties that are themselves a function of the lipid order. Within each population, there was considerable variability in the lipid order and response between individual microbubbles, suggesting the need for improved manufacturing techniques. In addition, the difference in the lipid order between the shell and lipid debris may be important for therapeutic applications in which shedding of the shell material is exploited, for example, drug delivery.
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Affiliation(s)
- Richard J Browning
- Department of Engineering Science, Institute of Biomedical Engineering , University of Oxford , Oxford OX3 7DQ , U.K
| | - Miles Aron
- Department of Engineering Science, Institute of Biomedical Engineering , University of Oxford , Oxford OX3 7DQ , U.K
| | - Anna Booth
- Department of Engineering Science, Institute of Biomedical Engineering , University of Oxford , Oxford OX3 7DQ , U.K
- Department of Chemistry , University of Oxford , Oxford OX1 3QR , U.K
| | - Paul Rademeyer
- Department of Engineering Science, Institute of Biomedical Engineering , University of Oxford , Oxford OX3 7DQ , U.K
| | - Sarah Wing
- Department of Engineering Science, Institute of Biomedical Engineering , University of Oxford , Oxford OX3 7DQ , U.K
| | - Veerle Brans
- Department of Engineering Science, Institute of Biomedical Engineering , University of Oxford , Oxford OX3 7DQ , U.K
| | - Shamit Shrivastava
- Department of Engineering Science, Institute of Biomedical Engineering , University of Oxford , Oxford OX3 7DQ , U.K
| | - Dario Carugo
- Department of Engineering Science, Institute of Biomedical Engineering , University of Oxford , Oxford OX3 7DQ , U.K
- Faculty of Engineering and Physical Sciences , University of Southampton , Highfield, Southampton SO17 1BJ , U.K
| | - Eleanor Stride
- Department of Engineering Science, Institute of Biomedical Engineering , University of Oxford , Oxford OX3 7DQ , U.K
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Zhang J, Shrivastava S, Cleveland RO, Rabbitts TH. Lipid-mRNA Nanoparticle Designed to Enhance Intracellular Delivery Mediated by Shock Waves. ACS APPLIED MATERIALS & INTERFACES 2019; 11:10481-10491. [PMID: 30788952 PMCID: PMC6602409 DOI: 10.1021/acsami.8b21398] [Citation(s) in RCA: 29] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/12/2023]
Abstract
Cellular membranes are, in general, impermeable to macromolecules (herein referred to as macrodrugs, e.g., recombinant protein, expression plasmids, or mRNA), which is a major barrier for clinical translation of macrodrug-based therapies. Encapsulation of macromolecules in lipid nanoparticles (LNPs) can protect the therapeutic agent during transport through the body and facilitate the intracellular delivery via a fusion-based pathway. Furthermore, designing LNPs responsive to stimuli can make their delivery more localized, thus limiting the side effects. However, the principles and criteria for designing such nanoparticles remain unclear. We show that the thermodynamic state of the lipid membrane of the nanoparticle is a key design principle for acoustically responsive fusogenic nanoparticles. We have optimized a cationic LNP (designated LNPLH) with two different phase transitions near physiological conditions for delivering mRNA. A bicistronic mRNA encoding a single domain intracellular antibody fragment and green fluorescent protein (GFP) was introduced into a range of human cancer cell types using LNPLH, and the protein expression was measured via fluorescence corresponding to the GFP expression. The LNPLH/mRNA complex demonstrated low toxicity and high delivery, which was significantly enhanced when the transfection occurred in the presence of acoustic shock waves. The results suggest that the thermodynamic state of LNPs provides an important criterion for stimulus responsive fusogenic nanoparticles to deliver macrodrugs to the inside of cells.
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Affiliation(s)
- Jing Zhang
- MRC Molecular Haematology
Unit, MRC Weatherall Institute of Molecular Medicine, Radcliffe Department
of Medicine, University of Oxford, John
Radcliffe Hospital, Oxford OX3 9DS, U.K.
| | - Shamit Shrivastava
- Institute
of Biomedical Engineering, University of
Oxford, Old Road Campus Research Building, Oxford OX3 7DQ, U.K.
| | - Robin O. Cleveland
- Institute
of Biomedical Engineering, University of
Oxford, Old Road Campus Research Building, Oxford OX3 7DQ, U.K.
- E-mail: (R.O.C.)
| | - Terence H. Rabbitts
- MRC Molecular Haematology
Unit, MRC Weatherall Institute of Molecular Medicine, Radcliffe Department
of Medicine, University of Oxford, John
Radcliffe Hospital, Oxford OX3 9DS, U.K.
- E-mail: (T.H.R.)
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