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Dharmadana D, Adamcik J, Ryan TM, Appiah Danso S, Chong CJH, Conn CE, Reynolds NP, Mezzenga R, Valéry C. Human neuropeptide substance P self-assembles into semi-flexible nanotubes that can be manipulated for nanotechnology. NANOSCALE 2020; 12:22680-22687. [PMID: 33165459 DOI: 10.1039/d0nr05622g] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Substance P neuropeptide is here reported to self-assemble into well-defined semi-flexible nanotubes. Using a blend of synchrotron small angle X-ray scattering, atomic force microscopy and other biophysical techniques, the natural peptide is shown to self-assemble into monodisperse 6 nm wide nanotubes, which can closely associate into nano-arrays with nematic properties. Using simple protocols, the nanotubes could be precipitated or mineralised while conserving their dimensions and core-shell morphology. Our discovery expands the small number of available monodisperse peptide nanotube systems for nanotechnology, beyond direct relevance to biologically functional peptide nanostructures since the substance P nanotubes are fundamentally different from typical amyloid fibrils.
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Meikle TG, Keizer DW, Babon JJ, Drummond CJ, Separovic F, Conn CE, Yao S. Physiochemical Characterization and Stability of Lipidic Cubic Phases by Solution NMR. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2020; 36:6254-6260. [PMID: 32418433 DOI: 10.1021/acs.langmuir.0c00949] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Lipidic inverse bicontinuous cubic phases (LCPs), formed via the spontaneous self-assembly of lipids such as monoolein, have found increasing applications in the stabilization and crystallization of integral membrane proteins for structural characterization using X-ray crystallography. Their use as effective drug release matrices has also been demonstrated. Nuclear magnetic resonance (NMR) spectroscopy, both solution and solid state, has previously been employed for the characterization of LCPs and related systems. Herein, we report a number of novel features of solution NMR for probing the fundamental composition and structural properties of monoolein-based LCPs. These include (1) more complete assignments of both 1H and 13C chemical shifts, (2) direct quantification of hydration level in LCPs using one-dimensional (1D) 1H NMR, and (3) monitoring longer-term stability of LCPs and evaluating alterations introduced into standard LCPs at the submolecular level.
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Sarkar S, Tran N, Soni SK, Conn CE, Drummond CJ. Size-Dependent Encapsulation and Release of dsDNA from Cationic Lyotropic Liquid Crystalline Cubic Phases. ACS Biomater Sci Eng 2020; 6:4401-4413. [DOI: 10.1021/acsbiomaterials.0c00085] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Meikle TG, Dyett BP, Strachan JB, White J, Drummond CJ, Conn CE. Preparation, Characterization, and Antimicrobial Activity of Cubosome Encapsulated Metal Nanocrystals. ACS APPLIED MATERIALS & INTERFACES 2020; 12:6944-6954. [PMID: 31917545 DOI: 10.1021/acsami.9b21783] [Citation(s) in RCA: 49] [Impact Index Per Article: 12.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Herein, we demonstrate a method for the functionalization of cubic phase lipid nanoparticles (cubosomes) with a series of magnetite (Fe3O4), copper oxide (Cu2O), and silver (Ag) nanocrystals, with prospective applications across a wide range of fields, including antimicrobial treatments. The resulting cubosomes are characterized using small-angle X-ray scattering and dynamic light scattering, demonstrating the retention of a typical cubic phase structure and particle size following nanocrystal encapsulation at concentrations up to 20% w/w. Cryogenic transmission electron microscopy reveals significant loading and association of each nanocrystal type with both monoolein- and phytantriol-based cubosomes. The antibiotic potential of these hybrid nanoparticles is demonstrated for the first time; cubosomes with embedded silver nanocrystals display a high level of antimicrobial activity against both Gram-positive and Gram-negative bacteria, with observed minimum inhibitory concentration values ranging from 15.6-250 μg/mL. Lastly, total internal reflection fluorescence microscopy is used to visualize cubosome-bacteria interactions, suggesting the involvement of particle interactions as a delivery mechanism.
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Strachan JB, Dharmadana D, Dyett BP, Valéry C, Conn CE. Encapsulation and Controlled Release of the Therapeutic Neuropeptides Somatostatin and Oxytocin from the Lipidic Bicontinuous Cubic Phase. Aust J Chem 2020. [DOI: 10.1071/ch19573] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Meikle TG, Drummond CJ, Conn CE. Microfluidic Synthesis of Rifampicin Loaded PLGA Nanoparticles and the Effect of Formulation on their Physical and Antibacterial Properties. Aust J Chem 2020. [DOI: 10.1071/ch19359] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
The encapsulation of drugs in nanoparticles serves as an effective way to modify pharmacokinetics and therapeutic efficacy. Nanoparticles comprised of poly(d,l-lactide-co-glycolide) (PLGA) are well suited for this purpose; they are accessible using multiple synthesis methods, are highly biocompatible and biodegradable, and possess desirable drug release properties. In the present study, we have explored the effects of various formulation parameters on the physical properties of PLGA nanoparticles synthesised using a microfluidic assisted nanoprecipitation method and loaded with a model drug. PLGA nanoparticles, with diameters ranging from 165–364nm, were produced using three alternate stabilisers; poly(vinyl alcohol) (PVA), d-α-tocopheryl polyethylene glycol 1000 succinate (TPGS), and didodecyldimethylammonium bromide (DMAB). Three additional formulations used PVA in addition to 20wt-% 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP), 1,2-di-O-octadecenyl-3-trimethylammonium propane (DOTMA), and oleic acid. Spectrophotometric analysis demonstrated that the use of PVA increased the loading efficiency over that of TPGS and DMAB formulations, while the inclusion of oleic acid in the PVA formulation resulted in a further 3-fold increase in loading efficiency. Invitro release studies demonstrate that the inclusion of lipid additives significantly alters release kinetics; release was most rapid and complete in the formulation containing oleic acid, while the addition of DOTAP and DOTMA significantly reduced release rates. Finally, the antimicrobial activity of each formulation was tested against Staphylococcus aureus and Bacillus cereus, with minimum inhibitory concentrations nearing or exceeding that of free rifampicin.
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Dyett BP, Yu H, Strachan J, Drummond CJ, Conn CE. Fusion dynamics of cubosome nanocarriers with model cell membranes. Nat Commun 2019; 10:4492. [PMID: 31582802 PMCID: PMC6776645 DOI: 10.1038/s41467-019-12508-8] [Citation(s) in RCA: 64] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2019] [Accepted: 09/12/2019] [Indexed: 12/24/2022] Open
Abstract
Drug delivery with nanocarriers relies on the interaction of individual nanocarriers with the cell surface. For lipid-based NCs, this interaction uniquely involves a process of membrane fusion between the lipid bilayer that makes up the NC and the cell membrane. Cubosomes have emerged as promising fusogenic NCs, however their individual interactions had not yet been directly observed due to difficulties in achieving adequate resolution or disentangling multiple interactions with common characterization techniques. Moreover, many studies on these interactions have been performed under static conditions which may not mimic the actual transport of NCs. Herein we have observed fusion of lipid cubosome NCs with lipid bilayers under flow. Total internal reflection microscopy has allowed visualisation of the fusion event which was sensitive to the lipid compositions and rationalized by lipid diffusion. The fusion event in supported lipid bilayers has been compared with those in cells, revealing a distinct similarity in kinetics.
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Meikle TG, Sethi A, Keizer DW, Babon JJ, Separovic F, Gooley PR, Conn CE, Yao S. Heteronuclear NMR spectroscopy of proteins encapsulated in cubic phase lipids. JOURNAL OF MAGNETIC RESONANCE (SAN DIEGO, CALIF. : 1997) 2019; 305:146-151. [PMID: 31284168 DOI: 10.1016/j.jmr.2019.06.017] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/03/2019] [Revised: 06/24/2019] [Accepted: 06/29/2019] [Indexed: 06/09/2023]
Abstract
Lipidic cubic phases, which form spontaneously via the self-assembly of certain lipids in an aqueous environment, are highly prospective nanomaterials with applications in membrane protein X-ray crystallography and drug delivery. Here we report 1H-15N heteronuclear single/multiple quantum coherence (HSQC, HMQC) spectra of 15N-enriched proteins encapsulated in inverse bicontinuous lipidic cubic phases obtained on a standard commercial high resolution NMR spectrometer at ambient temperature. 15N-enriched proteins encapsulated in this lipidic cubic phase show: (i) no significant changes in tertiary structure, (ii) significantly reduced solvent chemical exchange of backbone amides, which potentially provides a novel concept for quantifying residue-specific hydration; and (iii) improved spectral sensitivity achieved with band-selective excitation short-transient (BEST) spectroscopy, which is attributed to the presence of an abundant source of 1H nuclear spins originating from the lipid component of the cubic phase.
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Dharmadana D, Reynolds NP, Conn CE, Valéry C. pH-Dependent Self-Assembly of Human Neuropeptide Hormone GnRH into Functional Amyloid Nanofibrils and Hexagonal Phases. ACS APPLIED BIO MATERIALS 2019; 2:3601-3606. [DOI: 10.1021/acsabm.9b00468] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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van T Hag L, de Campo L, Tran N, Sokolova A, Trenker R, Call ME, Call MJ, Garvey CJ, Leung AE, Darwish TA, Krause-Heuer A, Knott R, Meikle TG, Drummond CJ, Mezzenga R, Conn CE. Protein-Eye View of the in Meso Crystallization Mechanism. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2019; 35:8344-8356. [PMID: 31122018 DOI: 10.1021/acs.langmuir.9b00647] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/09/2023]
Abstract
For evolving biological and biomedical applications of hybrid protein?lipid materials, understanding the behavior of the protein within the lipid mesophase is crucial. After more than two decades since the invention of the in meso crystallization method, a protein-eye view of its mechanism is still lacking. Numerous structural studies have suggested that integral membrane proteins preferentially partition at localized flat points on the bilayer surface of the cubic phase with crystal growth occurring from a local fluid lamellar L? phase conduit. However, studies to date have, by necessity, focused on structural transitions occurring in the lipid mesophase. Here, we demonstrate using small-angle neutron scattering that the lipid bilayer of monoolein (the most commonly used lipid for in meso crystallization) can be contrast-matched using deuteration, allowing us to isolate scattering from encapsulated peptides during the crystal growth process for the first time. During in meso crystallization, a clear decrease in form factor scattering intensity of the peptides was observed and directly correlated with crystal growth. A transient fluid lamellar L? phase was observed, providing direct evidence for the proposed mechanism for this technique. This suggests that the peptide passes through a transition from the cubic QII phase, via an L? phase to the lamellar crystalline Lc phase with similar layered spacing. When high protein loading was possible, the lamellar crystalline Lc phase of the peptide in the single crystals was observed. These findings show the mechanism of in meso crystallization for the first time from the perspective of integral membrane proteins.
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Chang C, Meikle TG, Su Y, Wang X, Dekiwadia C, Drummond CJ, Conn CE, Yang Y. Encapsulation in egg white protein nanoparticles protects anti-oxidant activity of curcumin. Food Chem 2019; 280:65-72. [DOI: 10.1016/j.foodchem.2018.11.124] [Citation(s) in RCA: 70] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2018] [Revised: 11/21/2018] [Accepted: 11/22/2018] [Indexed: 11/15/2022]
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Sarkar S, Tran N, Rashid MH, Le TC, Yarovsky I, Conn CE, Drummond CJ. Toward Cell Membrane Biomimetic Lipidic Cubic Phases: A High-Throughput Exploration of Lipid Compositional Space. ACS APPLIED BIO MATERIALS 2018; 2:182-195. [DOI: 10.1021/acsabm.8b00539] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
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Dharmadana D, Reynolds NP, Dekiwadia C, Conn CE, Valéry C. Heparin assisted assembly of somatostatin amyloid nanofibrils results in disordered precipitates by hindrance of protofilaments interactions. NANOSCALE 2018; 10:18195-18204. [PMID: 30141801 DOI: 10.1039/c8nr02159g] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
Amyloid nanofibrils are β-sheet rich protein or peptide assemblies that have pathological roles in over 20 neurodegenerative diseases, but also can have essential physiological roles. This wide variety of functions is likely to be due to subtle differences in amyloid structure and assembly mechanisms. Glycosaminoglycans (GAGs), like heparin, are frequently used in vitro to increase the kinetics of assembly of amyloid fibrils. However, little is known about the effects of adding large polymeric sugars on assembly mechanisms and amyloid nanostructures. Here, we provide insights into the kinetics, assembly mechanisms and structural effects of heparin on the self-assembly of a functional-amyloid forming neuropeptide hormone, somatostatin-14. We show that pure somatostatin-14 self-assembles into amyloid fibrils via the formation of antiparallel β-sheet networks, in a typical amyloid aggregation process. These fibrils then laterally assemble into ordered liquid crystalline structures through the generation of further parallel β-sheet networks. If heparin molecules are present, they intercalate between the peptide assemblies during the initial stages of aggregation. This intercalation screens electrostatic repulsions hindering the lateral association of protofilaments, preventing liquid crystal formation and resulting in the rapid formation of disordered micron scale precipitates. Our results show that aggregation promotors like heparin can have large effects not just on the kinetics of aggregation but also on assembly mechanisms, and the architecture of amyloid assemblies. Thus highlighting the dangers of using such polymeric sugars in fundamental studies of amyloid aggregation, especially when drawing conclusions on structure-function relationships or when investigating amyloid-based nanostructures as bionanomaterials.
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Dyett B, Zychowski L, Bao L, Meikle TG, Peng S, Yu H, Li M, Strachan J, Kirby N, Logan A, Conn CE, Zhang X. Crystallization of Femtoliter Surface Droplet Arrays Revealed by Synchrotron Small-Angle X-ray Scattering. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2018; 34:9470-9476. [PMID: 30021434 DOI: 10.1021/acs.langmuir.8b01252] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The crystallization of oil droplets is critical in the processing and storage of lipid-based food and pharmaceutical products. Arrays of femtoliter droplets on a surface offer a unique opportunity to study surfactant-free colloidlike systems. In this work, the crystal growth process in these confined droplets was followed by cooling a model lipid (trimyristin) from a liquid state utilizing synchrotron small-angle X-ray scattering (SAXS). The measurements by SAXS demonstrated a reduced crystallization rate and a greater degree of supercooling required to trigger lipid crystallization in droplets compared to those of bulk lipids. These results suggest that surface droplets crystallize in a stochastic manner. Interestingly, the crystallization rate is slower for larger femtoliter droplets, which may be explained by the onset of crystallization from the three-phase contact line. The larger surface nanodroplets exhibit a smaller ratio of droplet volume to the length of three-phase contact line and hence a slower crystallization rate.
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Tran N, Zhai J, Conn CE, Mulet X, Waddington LJ, Drummond CJ. Direct Visualization of the Structural Transformation between the Lyotropic Liquid Crystalline Lamellar and Bicontinuous Cubic Mesophase. J Phys Chem Lett 2018; 9:3397-3402. [PMID: 29809009 DOI: 10.1021/acs.jpclett.8b01110] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/08/2023]
Abstract
The transition between the lyotropic liquid crystalline lamellar and the bicontinuous cubic mesophase drives multiple fundamental cellular processes involving changes in cell membrane topology, including endocytosis and membrane budding. While several theoretical models have been proposed to explain this dynamic transformation, experimental validation of these models has been challenging because of the short-lived nature of the intermediates present during the phase transition. Herein, we report the direct observation of a lamellar-to-bicontinuous cubic phase transition in nanoscale dispersions using a combination of cryogenic transmission electron microscopy and static small-angle X-ray scattering. The results represent the first experimental confirmation of a theoretical model which proposed that the bicontinuous cubic phase originates from the center of a lamellar vesicle then propagates outward via the formation of interlamellar attachments and stalks. The observation was possible because of the precise control of the lipid composition to place the dispersion systems at the phase boundary of a lamellar and a cubic phase, allowing for the creation of long-lived structural intermediates. By the surveying of the nanoparticles using cryogenic transmission electron microscopy, a complete phase transition sequence was established.
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van 't Hag L, Gras SL, Conn CE, Drummond CJ. Lyotropic liquid crystal engineering moving beyond binary compositional space - ordered nanostructured amphiphile self-assembly materials by design. Chem Soc Rev 2018; 46:2705-2731. [PMID: 28280815 DOI: 10.1039/c6cs00663a] [Citation(s) in RCA: 119] [Impact Index Per Article: 19.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
Ordered amphiphile self-assembly materials with a tunable three-dimensional (3D) nanostructure are of fundamental interest, and crucial for progressing several biological and biomedical applications, including in meso membrane protein crystallization, as drug and medical contrast agent delivery vehicles, and as biosensors and biofuel cells. In binary systems consisting of an amphiphile and a solvent, the ability to tune the 3D cubic phase nanostructure, lipid bilayer properties and the lipid mesophase is limited. A move beyond the binary compositional space is therefore required for efficient engineering of the required material properties. In this critical review, the phase transitions upon encapsulation of more than 130 amphiphilic and soluble additives into the bicontinuous lipidic cubic phase under excess hydration are summarized. The data are interpreted using geometric considerations, interfacial curvature, electrostatic interactions, partition coefficients and miscibility of the alkyl chains. The obtained lyotropic liquid crystal engineering design rules can be used to enhance the formulation of self-assembly materials and provides a large library of these materials for use in biomedical applications (242 references).
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Dharmadana D, Reynolds NP, Conn CE, Valéry C. Molecular interactions of amyloid nanofibrils with biological aggregation modifiers: implications for cytotoxicity mechanisms and biomaterial design. Interface Focus 2017; 7:20160160. [PMID: 28630679 PMCID: PMC5474041 DOI: 10.1098/rsfs.2016.0160] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Amyloid nanofibrils are ubiquitous biological protein fibrous aggregates, with a wide range of either toxic or beneficial activities that are relevant to human disease and normal biology. Protein amyloid fibrillization occurs via nucleated polymerization, through non-covalent interactions. As such, protein nanofibril formation is based on a complex interplay between kinetic and thermodynamic factors. The process entails metastable oligomeric species and a highly thermodynamically favoured end state. The kinetics, and the reaction pathway itself, can be influenced by third party moieties, either molecules or surfaces. Specifically, in the biological context, different classes of biomolecules are known to act as catalysts, inhibitors or modifiers of the generic protein fibrillization process. The biological aggregation modifiers reviewed here include lipid membranes of varying composition, glycosaminoglycans and metal ions, with a final word on xenobiotic compounds. The corresponding molecular interactions are critically analysed and placed in the context of the mechanisms of cytotoxicity of the amyloids involved in diverse pathologies and the non-toxicity of functional amyloids (at least towards their biological host). Finally, the utilization of this knowledge towards the design of bio-inspired and biocompatible nanomaterials is explored.
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Meikle TG, Zabara A, Waddington LJ, Separovic F, Drummond CJ, Conn CE. Incorporation of antimicrobial peptides in nanostructured lipid membrane mimetic bilayer cubosomes. Colloids Surf B Biointerfaces 2017; 152:143-151. [DOI: 10.1016/j.colsurfb.2017.01.004] [Citation(s) in RCA: 54] [Impact Index Per Article: 7.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2016] [Revised: 11/27/2016] [Accepted: 01/03/2017] [Indexed: 11/28/2022]
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Feast GC, Lepitre T, Tran N, Conn CE, Hutt OE, Mulet X, Drummond CJ, Savage GP. Inverse hexagonal and cubic micellar lyotropic liquid crystalline phase behaviour of novel double chain sugar-based amphiphiles. Colloids Surf B Biointerfaces 2017; 151:34-38. [DOI: 10.1016/j.colsurfb.2016.12.004] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2016] [Revised: 11/04/2016] [Accepted: 12/06/2016] [Indexed: 12/25/2022]
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Meikle TG, Yao S, Zabara A, Conn CE, Drummond CJ, Separovic F. Predicting the release profile of small molecules from within the ordered nanostructured lipidic bicontinuous cubic phase using translational diffusion coefficients determined by PFG-NMR. NANOSCALE 2017; 9:2471-2478. [PMID: 28045170 DOI: 10.1039/c6nr07382d] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The ordered nanostructured lipidic bicontinuous cubic phase has demonstrated potential as a drug release material, due to its ability to encapsulate a wide variety of compounds, which may undergo sustained, diffusion controlled release over time. Control of drug release has been shown to depend on the nanostructural parameters of the lipid mesophase. Herein, the diffusion and release of two amino acids, encapsulated within a range of different lipidic cubic mesophases are investigated. Pulsed-field gradient NMR was used to determine the diffusion coefficient of the encapsulated amino acid, which was found to be correlated with the nanoscale diameter of the water channels within the cubic mesophase. This information was used to predict the release profiles of encapsulated compounds from within the cubic mesophase, which was verified by directly measuring the release of each amino acid in vitro. Predicted release profiles tracked reasonably close to the measured release profiles, indicating that NMR determined diffusion measurements can be used to predict release profiles.
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van 't Hag L, Anandan A, Seabrook SA, Gras SL, Drummond CJ, Vrielink A, Conn CE. Direct demonstration of lipid phosphorylation in the lipid bilayer of the biomimetic bicontinuous cubic phase using the confined enzyme lipid A phosphoethanolamine transferase. SOFT MATTER 2017; 13:1493-1504. [PMID: 28125111 DOI: 10.1039/c6sm02487d] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Retention of amphiphilic protein activity within the lipid bilayer membrane of the nanostructured biomimetic bicontinuous cubic phase is crucial for applications utilizing these hybrid protein-lipid self-assembly materials, such as in meso membrane protein crystallization and drug delivery. Previous work, mainly on soluble and membrane-associated enzymes, has shown that enzyme activity may be modified when immobilized, including membrane bound enzymes. The effect on activity may be even greater for amphiphilic enzymes with a large hydrophilic domain, such as the Neisserial enzyme lipid A phosphoethanolamine transferase (EptA). Encapsulation within the biomimetic but non-endogenous lipid bilayer membrane environment may modify the enzyme conformation, while confinement of the large hydrophilic domain with the nanoscale water channels of a continuous lipid bilayer structure may prevent full function of this enzyme. Herein we show that NmEptA remains active despite encapsulation within a nanostructured bicontinuous cubic phase. Full transfer of the phosphoethanolamine (PEA) group from a 1,2-dioleoyl-glycero-phosphoethanolamine (DOPE) doped lipid to monoolein (MO), which makes up the bicontinuous cubic phase, is shown. The reaction was found to be non-specific to the alkyl chain identity. The observed rate of enzyme activity is similar to other membrane bound enzymes, with complete transfer of the PEA group occurring in vitro, under the conditions studied, over a 24 hour timescale.
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Zabara A, Meikle TG, Newman J, Peat TS, Conn CE, Drummond CJ. The nanoscience behind the art of in-meso crystallization of membrane proteins. NANOSCALE 2017; 9:754-763. [PMID: 27976759 DOI: 10.1039/c6nr07634c] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
The structural changes occurring at the nanoscale level within the lipid bilayer and driving the in-meso formation of large well-diffracting membrane protein crystals have been uniquely characterized for a model membrane protein, intimin. Importantly, the order to order transitions taking place within the bilayer and the lipidic nanostructures required for crystal growth have been shown to be general, occurring for both the cubic and the sponge mesophase crystallization pathways. For the first time, a transient fluid lamellar phase has been observed and unambiguously assigned for both crystallization pathways, present at the earliest stages of protein crystallogenesis but no longer observed once the crystals surpass the size of the average lyotropic liquid crystalline domain. The reported time-resolved structural investigation provides a significantly improved and general understanding of the nanostructural changes taking place within the mesophase during in-meso crystallization which is a fundamental advance in the enabling area of membrane protein structural biology.
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van 't Hag L, Shen HH, Lin TW, Gras SL, Drummond CJ, Conn CE. Effect of Lipid-Based Nanostructure on Protein Encapsulation within the Membrane Bilayer Mimetic Lipidic Cubic Phase Using Transmembrane and Lipo-proteins from the Beta-Barrel Assembly Machinery. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2016; 32:12442-12452. [PMID: 27326898 DOI: 10.1021/acs.langmuir.6b01800] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
A fundamental understanding of the effect of amphiphilic protein encapsulation on the nanostructure of the bicontinuous cubic phase is crucial to progressing biomedical and biological applications of these hybrid protein-lipid materials, including as drug delivery vehicles, as biosensors, biofuel cells and for in meso crystallization. The relationship between the lipid nanomaterial and the encapsulated protein, however, remains poorly understood. In this study, we investigated the effect of incorporating the five transmembrane and lipo-proteins which make up the β-barrel assembly machinery from Gram-negative bacteria within a series of bicontinuous cubic phases. The transmembrane β-barrel BamA caused an increase in lattice parameter of the cubic phase upon encapsulation. By contrast, the mainly hydrophilic lipo-proteins BamB-E caused the cubic phase lattice parameters to decrease, despite their large size relative to the diameter of the cubic phase water channels. Analysis of the primary amino acid sequence was used to rationalize this effect, based on specific interactions between aromatic amino acids within the proteins and the polar-apolar interface. Other factors that were found to have an effect were lateral bilayer pressure and rigidity within the lipid bilayer, water channel diameter, and size and structure of the lipo-proteins. The data presented suggest that hydrophilic bioactive molecules can be selectively encapsulated within the cubic phase by using a lipid anchor or aromatic amino acids, for drug delivery or biosensing applications.
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Zychowski LM, Logan A, Augustin MA, Kelly AL, Zabara A, O'Mahony JA, Conn CE, Auty MAE. Effect of Phytosterols on the Crystallization Behavior of Oil-in-Water Milk Fat Emulsions. JOURNAL OF AGRICULTURAL AND FOOD CHEMISTRY 2016; 64:6546-6554. [PMID: 27476512 DOI: 10.1021/acs.jafc.6b01722] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
Milk has been used commercially as a carrier for phytosterols, but there is limited knowledge on the effect of added plant sterols on the properties of the system. In this study, phytosterols dispersed in milk fat at a level of 0.3 or 0.6% were homogenized with an aqueous dispersion of whey protein isolate (WPI). The particle size, morphology, ζ-potential, and stability of the emulsions were investigated. Emulsion crystallization properties were examined through the use of differential scanning calorimetry (DSC) and Synchrotron X-ray scattering at both small and wide angles. Phytosterol enrichment influenced the particle size and physical appearance of the emulsion droplets, but did not affect the stability or charge of the dispersed particles. DSC data demonstrated that, at the higher level of phytosterol addition, crystallization of milk fat was delayed, whereas, at the lower level, phytosterol enrichment induced nucleation and emulsion crystallization. These differences were attributed to the formation of separate phytosterol crystals within the emulsions at the high phytosterol concentration, as characterized by Synchrotron X-ray measurements. X-ray scattering patterns demonstrated the ability of the phytosterol to integrate within the milk fat triacylglycerol matrix, with a concomitant increase in longitudinal packing and system disorder. Understanding the consequences of adding phytosterols, on the physical and crystalline behavior of emulsions may enable the functional food industry to design more physically and chemically stable products.
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van 't Hag L, Knoblich K, Seabrook SA, Kirby NM, Mudie ST, Lau D, Li X, Gras SL, Mulet X, Call ME, Call MJ, Drummond CJ, Conn CE. Exploring the in meso crystallization mechanism by characterizing the lipid mesophase microenvironment during the growth of single transmembrane α-helical peptide crystals. PHILOSOPHICAL TRANSACTIONS. SERIES A, MATHEMATICAL, PHYSICAL, AND ENGINEERING SCIENCES 2016; 374:rsta.2015.0125. [PMID: 27298442 PMCID: PMC4920275 DOI: 10.1098/rsta.2015.0125] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Accepted: 02/12/2016] [Indexed: 05/19/2023]
Abstract
The proposed mechanism for in meso crystallization of transmembrane proteins suggests that a protein or peptide is initially uniformly dispersed in the lipid self-assembly cubic phase but that crystals grow from a local lamellar phase, which acts as a conduit between the crystal and the bulk cubic phase. However, there is very limited experimental evidence for this theory. We have developed protocols to investigate the lipid mesophase microenvironment during crystal growth using standard procedures readily available in crystallography laboratories. This technique was used to characterize the microenvironment during crystal growth of the DAP12-TM peptide using synchrotron small angle X-ray scattering (SAXS) with a micro-sized X-ray beam. Crystal growth was found to occur from the gyroid cubic mesophase. For one in four crystals, a highly oriented local lamellar phase was observed, providing supporting evidence for the proposed mechanism for in meso crystallization. A new observation of this study was that we can differentiate diffraction peaks from crystals grown in meso, from peaks originating from the surrounding lipid matrix, potentially opening up the possibility of high-throughput SAXS analysis of in meso grown crystals.This article is part of the themed issue 'Soft interfacial materials: from fundamentals to formulation'.
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