1
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Pani I, Sil S, Pal SK. Liquid Crystal Biosensors: A New Therapeutic Window to Point-of-Care Diagnostics. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2023; 39:909-917. [PMID: 36634050 DOI: 10.1021/acs.langmuir.2c02959] [Citation(s) in RCA: 4] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/17/2023]
Abstract
After revolutionizing the field of electro-optic displays, liquid crystals (LCs) are emerging as functional soft materials with wide-ranging biomedical implications. Integrating smart sensor designs with label-free imaging presents exciting opportunities in diagnostics. In this Perspective, we present an elegant collage of the key findings that demonstrate the utility of LC biosensors in diagnosing a disease or infection in clinical samples, cellular microenvironments, or bodily fluids. We emphasize the currently prevalent diagnostic techniques and the advances made using LCs in achieving greater sensitivity, a simplified strategy, multiplexed detection, and so on. We collate the landmark contributions in translational research in LC-based diagnostics. We believe that developing LC-based biosensors presents a new therapeutic window in point-of-care diagnostics.
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Affiliation(s)
- Ipsita Pani
- Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER) Mohali, Mohali 140306, Punjab, India
| | - Soma Sil
- Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER) Mohali, Mohali 140306, Punjab, India
| | - Santanu Kumar Pal
- Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER) Mohali, Mohali 140306, Punjab, India
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2
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Manna U, Zavala YM, Abbott NL, Lynn DM. Structured Liquid Droplets as Chemical Sensors that Function Inside Living Cells. ACS APPLIED MATERIALS & INTERFACES 2021; 13:42502-42512. [PMID: 34469102 DOI: 10.1021/acsami.1c12667] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/13/2023]
Abstract
We report that micrometer-scale droplets of thermotropic liquid crystals (LCs) can be positioned inside living mammalian cells and deployed as chemical sensors to report the presence of toxins in extracellular environments. Our approach exploits droplets of LC enclosed in semi-permeable polymer capsules that enable internalization by cells. The LC droplets are stable in intracellular environments, but undergo optical changes upon exposure of cells to low, sub-lethal concentrations of toxic amphiphiles. Remarkably, LC droplets in intracellular environments respond to extracellular analytes that do not generate an LC response in the absence of cellular internalization. They also do not respond to other chemical stimuli or processes associated with cell growth or manipulation in culture. Our results suggest that droplet activation involves the transport and co-adsorption of amphiphilic toxins and other lipophilic cell components to the surfaces of internalized droplets. This work provides fundamentally new designs of biotic-abiotic systems that can report sensitively and selectively on the presence of select chemical agents outside cells and provides a foundation for the design of structured liquid droplets that can sense and report on other biochemical or metabolic processes inside cells.
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Affiliation(s)
- Uttam Manna
- Department of Chemical and Biological Engineering, University of Wisconsin-Madison, 1415 Engineering Dr., Madison, Wisconsin 53706, United States
| | - Yashira M Zavala
- Department of Chemical and Biological Engineering, University of Wisconsin-Madison, 1415 Engineering Dr., Madison, Wisconsin 53706, United States
| | - Nicholas L Abbott
- Department of Chemical and Biological Engineering, University of Wisconsin-Madison, 1415 Engineering Dr., Madison, Wisconsin 53706, United States
| | - David M Lynn
- Department of Chemical and Biological Engineering, University of Wisconsin-Madison, 1415 Engineering Dr., Madison, Wisconsin 53706, United States
- Department of Chemistry, University of Wisconsin-Madison, 1101 University Avenue, Madison, Wisconsin 53706, United States
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3
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Pani I, K M FN, Sharma M, Pal SK. Probing Nanoscale Lipid-Protein Interactions at the Interface of Liquid Crystal Droplets. NANO LETTERS 2021; 21:4546-4553. [PMID: 34048245 DOI: 10.1021/acs.nanolett.0c05139] [Citation(s) in RCA: 16] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
Abstract
Aqueous interfaces of liquid crystals (LCs) are widely explored in the design of functional interfaces to recapitulate the key aspects of biomolecular interactions in cellular milieu. Herein, using aqueous LC dispersions, we explore the interactions between mitochondrial cardiolipin and membrane-associated cytochrome c which play a pivotal role in the apoptotic signaling cascade. Conventional techniques used to decipher LC ordering at the droplet interface fail to give information about the interactions at a molecular level. Besides, owing to the complexity of LC systems and multiple determinants driving the LC reorientation, accurate analysis of the underlying mechanism responsible for the LC ordering transition remains challenging. Using a combination of atomistic simulations and microscopic and spectroscopic readouts, for the first time, we unveil the lipid-protein interactions that drive the reorientation at the LC droplet interface. The insights from our work are fundamental to the design of these interfaces for a spectrum of interfacial applications.
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4
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Wang Z, Xu T, Noel A, Chen YC, Liu T. Applications of liquid crystals in biosensing. SOFT MATTER 2021; 17:4675-4702. [PMID: 33978639 DOI: 10.1039/d0sm02088e] [Citation(s) in RCA: 45] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/21/2023]
Abstract
Liquid crystals (LCs), as a promising branch of highly-sensitive, quick-response, and low-cost materials, are widely applied to the detection of weak external stimuli and have attracted significant attention. Over the past decade, many research groups have been devoted to developing LC-based biosensors due to their self-assembly potential and functional diversity. In this paper, recent investigations on the design and application of LC-based biosensors are reviewed, based on the phenomenon that the orientation of LCs can be directly influenced by the interactions between biomolecules and LC molecules. The sensing principle of LC-based biosensors, as well as their signal detection by probing interfacial interactions, is described to convert, amplify, and quantify the information from targets into optical and electrical parameters. Furthermore, commonly-used LC biosensing targets are introduced, including glucose, proteins, enzymes, nucleic acids, cells, microorganisms, ions, and other micromolecules that are critical to human health. Due to their self-assembly potential, chemical diversity, and high sensitivity, it has been reported that tunable stimuli-responsive LC biosensors show bright perspectives and high superiorities in biological applications. Finally, challenges and future prospects are discussed for the fabrication and application of LC biosensors to both enhance their performance and to realize their promise in the biosensing industry.
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Affiliation(s)
- Ziyihui Wang
- School of Precision Instrument and Opto-Electronics Engineering, Tianjin University, Tianjin, 300072, China.
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5
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Wilson BA, Ramanathan A, Lopez CF. Cardiolipin-Dependent Properties of Model Mitochondrial Membranes from Molecular Simulations. Biophys J 2019; 117:429-444. [PMID: 31349988 PMCID: PMC6697365 DOI: 10.1016/j.bpj.2019.06.023] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/22/2019] [Revised: 06/17/2019] [Accepted: 06/24/2019] [Indexed: 01/30/2023] Open
Abstract
Cardiolipin is an anionic lipid found in the mitochondrial membranes of eukaryotes ranging from unicellular microorganisms to metazoans. This unique lipid contributes to various mitochondrial functions, including metabolism, mitochondrial membrane fusion and/or fission dynamics, and apoptosis. However, differences in cardiolipin content between the two mitochondrial membranes, as well as dynamic fluctuations in cardiolipin content in response to stimuli and cellular signaling events, raise questions about how cardiolipin concentration affects mitochondrial membrane structure and dynamics. Although cardiolipin’s structural and dynamic roles have been extensively studied in binary mixtures with other phospholipids, the biophysical properties of cardiolipin in higher number lipid mixtures are still not well resolved. Here, we used molecular dynamics simulations to investigate the cardiolipin-dependent properties of ternary lipid bilayer systems that mimic the major components of mitochondrial membranes. We found that changes to cardiolipin concentration only resulted in minor changes to bilayer structural features but that the lipid diffusion was significantly affected by those alterations. We also found that cardiolipin position along the bilayer surfaces correlated to negative curvature deflections, consistent with the induction of negative curvature stress in the membrane monolayers. This work contributes to a foundational understanding of the role of cardiolipin in altering the properties in ternary lipid mixtures composed of the major mitochondrial phospholipids, providing much-needed insights to help understand how cardiolipin concentration modulates the biophysical properties of mitochondrial membranes.
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Affiliation(s)
- Blake A Wilson
- Department of Biochemistry, Vanderbilt University, Nashville, Tennessee
| | - Arvind Ramanathan
- Computational Science and Engineering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee; Health Data Sciences Institute, Oak Ridge National Laboratory, Oak Ridge, Tennessee
| | - Carlos F Lopez
- Department of Biochemistry, Vanderbilt University, Nashville, Tennessee; Department of Biomedical Informatics, Vanderbilt University Medical Center, Nashville, Tennessee; Department of Pharmacology, Vanderbilt University, Nashville, Tennessee.
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6
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Boyd KJ, Alder NN, May ER. Molecular Dynamics Analysis of Cardiolipin and Monolysocardiolipin on Bilayer Properties. Biophys J 2019; 114:2116-2127. [PMID: 29742405 DOI: 10.1016/j.bpj.2018.04.001] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2017] [Revised: 03/04/2018] [Accepted: 04/02/2018] [Indexed: 11/29/2022] Open
Abstract
The mitochondrial lipid cardiolipin (CL) contributes to the spatial protein organization and morphological character of the inner mitochondrial membrane. Monolysocardiolipin (MLCL), an intermediate species in the CL remodeling pathway, is enriched in the multisystem disease Barth syndrome. Despite the medical relevance of MLCL, a detailed molecular description that elucidates the structural and dynamic differences between CL and MLCL has not been conducted. To this end, we performed comparative atomistic molecular dynamics studies on bilayers consisting of pure CL or MLCL to elucidate similarities and differences in their molecular and bulk bilayer properties. We describe differential headgroup dynamics and hydrogen bonding patterns between the CL variants and show an increased cohesiveness of MLCL's solvent interfacial region, which may have implications for protein interactions. Finally, using the coarse-grained Martini model, we show that substitution of MLCL for CL in bilayers mimicking mitochondrial composition induces drastic differences in bilayer mechanical properties and curvature-dependent partitioning behavior. Together, the results of this work reveal differences between CL and MLCL at the molecular and mesoscopic levels that may underpin the pathomechanisms of defects in cardiolipin remodeling.
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Affiliation(s)
- Kevin J Boyd
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, Connecticut
| | - Nathan N Alder
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, Connecticut
| | - Eric R May
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, Connecticut.
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7
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Yang X, Tian Y, Li F, Yu Q, Tan SF, Chen Y, Yang Z. Investigation of the Assembly Behavior of an Amphiphilic Lipopeptide at the Liquid Crystal-Aqueous Interface. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:2490-2497. [PMID: 30696245 DOI: 10.1021/acs.langmuir.8b03294] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
In this article, we designed an amphiphilic lipopeptide molecule, 5(6)-carboxyfluorescein-KKKKKKSKTK-Cys(C12H25)-OMe (FAM-lipopeptide-C12), and studied its assembly behavior at the 4-cyano-4'-pentylbiphenyl (5CB)-aqueous interface. The ordering transitions of liquid crystals (LCs) revealed that FAM-lipopeptide-C12 can assemble at the LC-aqueous interface (both planar and curved interfaces). The assembly can be destroyed by adding trypsin, which catalyzes the hydrolysis of lipopeptides. Fluorescence measurements further confirmed the assembly and deassembly behavior of FAM-lipopeptide-C12 at the LC-aqueous interface. Overall, our work provides a general method for the construction of a biointerface by directly assembling amphiphilic lipopeptides at the LC-aqueous interface, which can potentially be used in selectively detecting the activity of specific enzymes and other biomolecular interactions.
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8
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Zhou L, Hu Q, Kang Q, Fang M, Yu L. Construction of a Liquid Crystal-Based Sensing Platform for Sensitive and Selective Detection of l-Phenylalanine Based on Alkaline Phosphatase. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:461-467. [PMID: 30576146 DOI: 10.1021/acs.langmuir.8b03682] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
The detection of l-phenylalanine (l-Phe) has become one of the most pressing issues concerning diagnosis and treatment of phenylketonuria in neonates; however, a simple and robust methodology is yet to be developed. Here, the application of novel liquid crystals (LCs)-sensing platform for sensitive, selective, and label-free detection of l-Phe was reported at the first time. We devised a strategy to fabricate the sodium monododecyl phosphate (SMP)-decorated LC sensing platform with the appearance of dark. Then, a dark to bright (D-B) optical images alteration of LCs was observed after transferring alkaline phosphatase (ALP) to the interface, owing to cleavage of SMP induced by ALP. LCs remained dark images after the SMP-decorated interface in contact with the pre-incubated ALP and l-Phe. Such optical appearance resulted from the inhibition of ALP by l-Phe, which was further verified by the isothermal titration calorimetry (ITC). The strategy was applied to sensing l-Phe, which have been proven to allow for sensitively and selectively differentiation of l-Phe from interfering compounds with similar aromatic groups, as well as seven other essential amino acids. More importantly, the detection limit of l-Phe reached 1 pg/mL in urine samples, further demonstrating its value in the practical applications. Results obtained in this study clearly demonstrated the superiority of LCs toward the l-Phe detection, which can pave a way for the development of high performance and robust probes for l-Phe detection in clinical applications.
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Affiliation(s)
- Lele Zhou
- Key Laboratory of Colloid and Interface Chemistry, Ministry of Education , Shandong University , Jinan 250100 , P.R. China
- School of Chemistry and Chemical Engineering , Qufu Normal University , Qufu 273165 , P.R. China
| | - Qiongzheng Hu
- Department of Chemistry , University of Houston , Houston , Texas 77204 , United States
| | - Qi Kang
- College of Chemistry, Chemical Engineering and Materials Science , Shandong Normal University , Jinan 250014 , P. R. China
| | - Ming Fang
- Department of Chemistry , University of Houston , Houston , Texas 77204 , United States
| | - Li Yu
- Key Laboratory of Colloid and Interface Chemistry, Ministry of Education , Shandong University , Jinan 250100 , P.R. China
- School of Chemistry and Chemical Engineering , Qufu Normal University , Qufu 273165 , P.R. China
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9
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Nandi R, Loitongbam L, De J, Jain V, Pal SK. Gold nanoparticle-mediated signal amplification of liquid crystal biosensors for dopamine. Analyst 2019; 144:1110-1114. [DOI: 10.1039/c8an02171f] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
A new design was developed for detection of dopamine using a boronic acid based amphiphile at aqueous–liquid crystal interface. The detection was highly enhanced in presence of gold nanoparticles.
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Affiliation(s)
- Rajib Nandi
- Department of Chemical Sciences
- Indian Institute of Science Education and Research (IISER) Mohali
- Manauli-140306
- India
| | - Lisha Loitongbam
- Department of Chemical Sciences
- Indian Institute of Science Education and Research (IISER) Mohali
- Manauli-140306
- India
| | - Joydip De
- Department of Chemical Sciences
- Indian Institute of Science Education and Research (IISER) Mohali
- Manauli-140306
- India
| | - Varsha Jain
- Department of Chemical Sciences
- Indian Institute of Science Education and Research (IISER) Mohali
- Manauli-140306
- India
| | - Santanu Kumar Pal
- Department of Chemical Sciences
- Indian Institute of Science Education and Research (IISER) Mohali
- Manauli-140306
- India
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10
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Abstract
Liquid crystal (LC) based optical sensors have been found to be very promising for detecting aqueous biological samples due to the ease of optical detection, their cost effectiveness and the removal of the need for labelling biological species with fluorescent dyes. To date, all LC based sensors are studied in laboratories using conventional polarizing optical microscopy (POM), and no attention has been paid towards the fabrication of portable LC sensing devices for use in commercial purposes. Here, we designed and fabricated a 3D printed portable, lightweight, and inexpensive sensing device using a smartphone to detect the optical signal of LC based sensors. The accuracy of the optical signal using the fabricated sensing device is similar to that obtained using conventional POM. The fabricated sensing device, using a smartphone, gives a novel and new platform to LC based sensors for practical applications in the industrial world and people's daily lives.
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Affiliation(s)
- Rajib Nandi
- Department of Chemical Sciences, Indian Institute of Science Education and Research (IISER) Mohali, Sector-81, Knowledge City, Manauli-140306, India.
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11
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Boyd KJ, Alder NN, May ER. Buckling Under Pressure: Curvature-Based Lipid Segregation and Stability Modulation in Cardiolipin-Containing Bilayers. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2017; 33:6937-6946. [PMID: 28628337 PMCID: PMC5654595 DOI: 10.1021/acs.langmuir.7b01185] [Citation(s) in RCA: 54] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2023]
Abstract
Mitochondrial metabolic function is affected by the morphology and protein organization of the mitochondrial inner membrane. Cardiolipin (CL) is a unique tetra-acyl lipid that is involved in the maintenance of the highly curved shape of the mitochondrial inner membrane as well as spatial organization of the proteins necessary for respiration and oxidative phosphorylation. Cardiolipin has been suggested to self-organize into lipid domains due to its inverted conical molecular geometry, though the driving forces for this organization are not fully understood. In this work, we use coarse-grained molecular dynamics simulations to study the mechanical properties and lipid dynamics in heterogeneous bilayers both with and without CL, as a function of membrane curvature. We find that incorporation of CL increases bilayer deformability and that CL becomes highly enriched in regions of high negative curvature. We further show that another mitochondrial inverted conical lipid, phosphatidylethanolamine (PE), does not partition or increase the deformability of the membrane in a significant manner. Therefore, CL appears to possess some unique characteristics that cannot be inferred simply from molecular geometry considerations.
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12
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Das D, Pal SK. Liquid Crystal Unveiled Interactions between Melittin and Phospholipids at Aqueous-Liquid Crystal Interface. ChemistrySelect 2017. [DOI: 10.1002/slct.201700604] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Affiliation(s)
- Dibyendu Das
- Department of Chemical Sciences; Indian Institute of Science Education and Research Mohali (IISERM), Sector-81, SAS Nagar, Knowledge City; Manauli- 140306 India
| | - Santanu Kumar Pal
- Department of Chemical Sciences; Indian Institute of Science Education and Research Mohali (IISERM), Sector-81, SAS Nagar, Knowledge City; Manauli- 140306 India
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13
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Sidiq S, Prasad GVRK, Mukhopadhaya A, Pal SK. Poly(l-lysine)-Coated Liquid Crystal Droplets for Cell-Based Sensing Applications. J Phys Chem B 2017; 121:4247-4256. [DOI: 10.1021/acs.jpcb.7b00551] [Citation(s) in RCA: 31] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Sumyra Sidiq
- Department
of Chemical Sciences and §Department of Biological Sciences, Indian Institute of Science Education and Research Mohali (IISERM), Knowledge
City, Sector-81, SAS Nagar, Mohali 140306, India
| | - G. V. R. Krishna Prasad
- Department
of Chemical Sciences and §Department of Biological Sciences, Indian Institute of Science Education and Research Mohali (IISERM), Knowledge
City, Sector-81, SAS Nagar, Mohali 140306, India
| | - Arunika Mukhopadhaya
- Department
of Chemical Sciences and §Department of Biological Sciences, Indian Institute of Science Education and Research Mohali (IISERM), Knowledge
City, Sector-81, SAS Nagar, Mohali 140306, India
| | - Santanu Kumar Pal
- Department
of Chemical Sciences and §Department of Biological Sciences, Indian Institute of Science Education and Research Mohali (IISERM), Knowledge
City, Sector-81, SAS Nagar, Mohali 140306, India
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14
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Popov P, Mann EK, Jákli A. Thermotropic liquid crystal films for biosensors and beyond. J Mater Chem B 2017; 5:5061-5078. [DOI: 10.1039/c7tb00809k] [Citation(s) in RCA: 118] [Impact Index Per Article: 16.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Recent results on structural properties and possible bio-sensing applications of planar liquid crystal films are reviewed.
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Affiliation(s)
- Piotr Popov
- Department of Physics
- Kent State University
- Kent
- USA
- Liquid Crystal Institute
| | | | - Antal Jákli
- Liquid Crystal Institute
- Kent State University
- Kent
- USA
- Complex Fluid Group
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15
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Sathappa M, Alder NN. The ionization properties of cardiolipin and its variants in model bilayers. BIOCHIMICA ET BIOPHYSICA ACTA-BIOMEMBRANES 2016; 1858:1362-72. [PMID: 26965987 DOI: 10.1016/j.bbamem.2016.03.007] [Citation(s) in RCA: 65] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/30/2015] [Revised: 02/25/2016] [Accepted: 03/03/2016] [Indexed: 01/01/2023]
Abstract
The anionic phospholipid cardiolipin has an unusual dimeric structure with a two-phosphate headgroup and four acyl chains. Cardiolipin is present in energy-transducing membranes that maintain electrochemical gradients, including most bacterial plasma membranes and the mitochondrial inner membrane, where it mediates respiratory complex assembly and activation, among many other roles. Dysfunctional biogenesis of cardiolipin is implicated in the pathogenesis of several diseases including Barth syndrome. Because cardiolipin is a dominant anionic lipid in energy-conserving membranes, its headgroup is a major contributor to surface charge density and the bilayer electrostatic profile. However, the proton dissociation behavior of its headgroup remains controversial. In one model, the pKa values of the phosphates differ by several units and the headgroup exists as a monoanion at physiological pH. In another model, both phosphates ionize as strong acids with low pKa values and the headgroup exists in dianionic form at physiological pH. Using independent electrokinetic and spectroscopic approaches, coupled with analysis using Gouy-Chapman-Stern formalism, we have analyzed the ionization properties of cardiolipin within biologically relevant lipid bilayer model systems. We show that both phosphates of the cardiolipin headgroup show strong ionization behavior with low pKa values. Moreover, cardiolipin variants lacking structural features proposed to be required to maintain disparate pKa values--namely the secondary hydroxyl on the central glycerol or a full complement of four acyl chains--were shown to have ionization behavior identical to intact cardiolipin. Hence, these results indicate that within the physiological pH range, the cardiolipin headgroup is fully ionized as a dianion. We discuss the implications of these results with respect to the role of cardiolipin in defining membrane surface potential, activating respiratory complexes, and modulating membrane curvature.
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Affiliation(s)
- Murugappan Sathappa
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, CT 06269, United States
| | - Nathan N Alder
- Department of Molecular and Cell Biology, University of Connecticut, Storrs, CT 06269, United States.
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16
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Guo X, Manna U, Abbott NL, Lynn DM. Covalent Immobilization of Caged Liquid Crystal Microdroplets on Surfaces. ACS APPLIED MATERIALS & INTERFACES 2015; 7:26892-903. [PMID: 26562466 DOI: 10.1021/acsami.5b09595] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/25/2023]
Abstract
Microscale droplets of thermotropic liquid crystals (LCs) suspended in aqueous media (e.g., LC-in-water emulsions) respond sensitively to the presence of contaminating amphiphiles and, thus, provide promising platforms for the development of new classes of droplet-based environmental sensors. Here, we report polymer-based approaches to the immobilization of LC droplets on surfaces; these approaches introduce several new properties and droplet behaviors and thus also expand the potential utility of LC droplet-based sensors. Our approach exploits the properties of microscale droplets of LCs contained within polymer-based microcapsule cages (so-called "caged" LCs). We demonstrate that caged LCs functionalized with primary amine groups can be immobilized on model surfaces through both weak/reversible ionic interactions and stronger reactive/covalent interactions. We demonstrate using polarized light microscopy that caged LCs that are covalently immobilized on surfaces can undergo rapid and diagnostic changes in shape, rotational mobility, and optical appearance upon the addition of amphiphiles to surrounding aqueous media, including many useful changes in these features that cannot be attained using freely suspended or surface-adsorbed LC droplets. Our results reveal these amphiphile-triggered orientational transitions to be reversible and that arrays of immobilized caged LCs can be used (and reused) to detect both increases and decreases in the concentrations of model contaminants. Finally, we report changes in the shapes and optical appearances of LC droplets that occur when immobilized caged LCs are removed from aqueous environments and dried, and we demonstrate that dried arrays can be stored for months without losing the ability to respond to the presence of analytes upon rehydration. Our results address practical issues associated with the preparation, characterization, storage, and point-of-use application of conventional LC-in-water emulsions and provide a basis for approaches that could enable the development of new "off-the-shelf" LC droplet-based sensing platforms.
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Affiliation(s)
- Xuanrong Guo
- Department of Chemical and Biological Engineering and ‡Department of Chemistry, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States
| | - Uttam Manna
- Department of Chemical and Biological Engineering and ‡Department of Chemistry, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States
| | - Nicholas L Abbott
- Department of Chemical and Biological Engineering and ‡Department of Chemistry, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States
| | - David M Lynn
- Department of Chemical and Biological Engineering and ‡Department of Chemistry, University of Wisconsin-Madison , Madison, Wisconsin 53706, United States
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17
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Mohiuddin G, Punjani V, Pal SK. Three-Ring-Based Room-Temperature Bent-Core Nematic Compounds: Synthesis and Characterization. Chemphyschem 2015. [DOI: 10.1002/cphc.201500435] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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18
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Das D, Sidiq S, Pal SK. Design of bio-molecular interfaces using liquid crystals demonstrating endotoxin interactions with bacterial cell wall components. RSC Adv 2015. [DOI: 10.1039/c5ra09640e] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
Liquid crystals offer a promising approach to study and quantify the interactions between different bacterial cell membrane components with endotoxin at an aqueous interface.
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Affiliation(s)
- Dibyendu Das
- Department of Chemical Sciences
- Indian Institute of Science Education and Research (IISER) Mohali
- India
| | - Sumyra Sidiq
- Department of Chemical Sciences
- Indian Institute of Science Education and Research (IISER) Mohali
- India
| | - Santanu Kumar Pal
- Department of Chemical Sciences
- Indian Institute of Science Education and Research (IISER) Mohali
- India
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