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Dabkowska AP, Collins LE, Barlow DJ, Barker R, McLain SE, Lawrence MJ, Lorenz CD. Modulation of dipalmitoylphosphatidylcholine monolayers by dimethyl sulfoxide. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2014; 30:8803-8811. [PMID: 25000494 DOI: 10.1021/la501275h] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The action of the penetration-enhancing agent, dimethyl sulfoxide (DMSO), on phospholipid monolayers was investigated at the air-water interface using a combination of experimental techniques and molecular dynamics simulations. Brewster angle microscopy revealed that DPPC monolayers remained laterally homogeneous at subphase concentrations up to a mole fraction of 0.1 DMSO. Neutron reflectometry of the monolayers in combination with isotopic substitution enabled the determination of solvent profiles as a function of distance perpendicular to the interface for the different DMSO subphase concentrations. These experimental results were compared to those obtained from molecular dynamic (MD) simulations of the corresponding monolayer systems. There was excellent agreement found between the MD-derived reflectivity curves and the measured data for all of the H/D contrast variations investigated. The MD provide a detailed description of the distribution of water and DMSO molecules around the phosphatidylcholine headgroup, and how this distribution changes with increasing DMSO concentrations. Significantly, the measurements and simulations that are reported here support the hypothesis that DMSO acts by dehydrating the phosphatidylcholine headgroup, and as such provide the first direct evidence that it does so primarily by displacing water molecules bound to the choline group.
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Mojumdar EH, Groen D, Gooris GS, Barlow DJ, Lawrence MJ, Deme B, Bouwstra JA. Localization of cholesterol and fatty acid in a model lipid membrane: a neutron diffraction approach. Biophys J 2014; 105:911-8. [PMID: 23972843 DOI: 10.1016/j.bpj.2013.07.003] [Citation(s) in RCA: 46] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2013] [Revised: 06/17/2013] [Accepted: 07/01/2013] [Indexed: 12/18/2022] Open
Abstract
The intercellular lipid matrix of the skin's stratum corneum serves to protect the body against desiccation and simultaneously limits the passage of drugs and other xenobiotics into the body. The matrix is made up of ceramides, free fatty acids, and cholesterol, which are organized as two coexisting crystalline lamellar phases. In studies reported here, we sought to use the technique of neutron diffraction, together with the device of isotopic (H/D) substitution, to determine the molecular architecture of the lamellar phase having a repeat distance of 53.9 ± 0.3 Å. Using hydrogenous samples as well as samples incorporating perdeuterated (C24:0) fatty acids and selectively deuterated cholesterol, the diffraction data obtained were used to construct neutron scattering length density profiles. By this means, the locations within the unit cell were determined for the cholesterol and fatty acids. The cholesterol headgroup was found to lie slightly inward from the unit cell boundary and the tail of the molecule located 6.2 ± 0.2 Å from the unit cell center. The fatty acid headgroups were located at the unit cell boundary with their acyl chains straddling the unit cell center. Based on these results, a molecular model is proposed for the arrangement of the lipids within the unit cell.
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Dabkowska AP, Barlow DJ, Clifton LA, Hughes AV, Webster JRP, Green RJ, Quinn PJ, Lawrence MJ. Calcium-mediated binding of DNA to 1,2-distearoyl-sn-glycero-3-phosphocholine-containing mixed lipid monolayers. SOFT MATTER 2014; 10:1685-1695. [PMID: 24652078 DOI: 10.1039/c3sm52747f] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
The calcium-mediated interaction of DNA with monolayers of the non-toxic, zwitterionic phospholipid, 1,2-distearoyl-sn-glycero-3-phosphocholine when mixed with 50 mol% of a second lipid, either the zwitteronic 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine or neutral cholesterol was investigated using a combination of surface pressure-area isotherms, Brewster angle microscopy, external reflectance Fourier transform infrared spectroscopy and specular neutron reflectivity in combination with contrast variation. When calcium and DNA were both present in the aqueous subphase, changes were observed in the compression isotherms as well as the surface morphologies of the mixed lipid monolayers. In the presence of calcium and DNA, specular neutron reflectivity showed that directly underneath the head groups of the lipids comprising the monolayers, DNA occupied a layer comprising approximately 13 and 18% v/v DNA for the 1,2-dioleoyl-sn-glycero-3-phosphoethanolamine and cholesterol-containing monolayers, respectively. The volume of the corresponding layer for 1,2-distearoyl-sn-glycero-3-phosphocholine only containing monolayers was ∼15% v/v DNA. Furthermore regardless of the presence and nature of the second lipid and the surface pressure of the monolayer, the specular neutron reflectivity experiments showed that the DNA-containing layer was 20-27 Å thick, suggesting the presence of a well-hydrated layer of double-stranded DNA. External reflectance Fourier transform infrared studies confirmed the presence of double stranded DNA, and indicated that the strands are in the B-form conformation. The results shed light on the interaction between lipids and nucleic acid cargo as well as the role of a second lipid in lipid-based carriers for drug delivery.
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Harvey RD, Ara N, Heenan RK, Barlow DJ, Quinn PJ, Lawrence MJ. Stabilization of distearoylphosphatidylcholine lamellar phases in propylene glycol using cholesterol. Mol Pharm 2013; 10:4408-17. [PMID: 24171434 DOI: 10.1021/mp400140u] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Phospholipid vesicles (liposomes) formed in pharmaceutically acceptable nonaqueous polar solvents such as propylene glycol are of interest in drug delivery because of their ability to improve the bioavailability of drugs with poor aqueous solubility. We have demonstrated a stabilizing effect of cholesterol on lamellar phases formed by dispersion of distearoylphosphatidylcholine (DSPC) in water/propylene glycol (PG) solutions with glycol concentrations ranging from 0 to 100%. The stability of the dispersions was assessed by determining the effect of propylene glycol concentration on structural parameters of the lamellar phases using a complementary combination of X-ray and neutron scattering techniques at 25 °C and in the case of X-ray scattering at 65 °C. Significantly, although stable lamellar phases (and liposomes) were formed in all PG solutions at 25 °C, the association of the glycol with the liposomes' lamellar structures led to the formation of interdigitated phases, which were not thermostable at 65 °C. With the addition of equimolar quantities of cholesterol to the dispersions of DSPC, stable lamellar dispersions (and indeed liposomes) were formed in all propylene glycol solutions at 25 °C, with the significant lateral phase separation of the bilayer components only detectable in propylene glycol concentrations above 60% (w/w). We propose that the stability of lamellar phases of the cholesterol-containing liposomes formed in propylene glycol concentrations of up to 60% (w/w) represent potentially very valuable drug delivery vehicles for a variety of routes of administration.
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Goodwin DJ, Sepassi S, King SM, Holland SJ, Martini LG, Lawrence MJ. Characterization of Polymer Adsorption onto Drug Nanoparticles Using Depletion Measurements and Small-Angle Neutron Scattering. Mol Pharm 2013; 10:4146-58. [DOI: 10.1021/mp400138e] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
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Wasutrasawat P, Al-Obaidi H, Gaisford S, Lawrence MJ, Warisnoicharoen W. Drug solubilisation in lipid nanoparticles containing high melting point triglycerides. Eur J Pharm Biopharm 2013; 85:365-71. [PMID: 23688806 DOI: 10.1016/j.ejpb.2013.04.020] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2013] [Revised: 04/20/2013] [Accepted: 04/25/2013] [Indexed: 11/25/2022]
Abstract
The effect of lipid (either the triglyceride trilaurin or tripalmitin, melting points of 43 and 64 °C, respectively) on the properties of lipid nanoparticles (LN) stabilised by the surfactant, polyoxyethylene-10-oleyl ether (C18:1E10) at a temperature of 22 °C, has been determined. LN were prepared by heating lipid, surfactant and water to 70 °C and cooling to ambient temperature with constant stirring. While lipid type influenced LN formation in that trilaurin-containing LN formed over the greatest range of compositions, phase inversion studies suggested that both lipids formed a core within the LN while light scattering studies indicated that the size of both types of LN varied with lipid concentration: in an approximately linear fashion for clear or opalescent LN and exponentially for cloudy LN. Additionally, both types of preformed LN exhibited an increase in solubilisation capacity of the hydrophobic drug, testosterone propionate compared to C18:1E10 micelles, although the trilaurin-containing LN exhibited the greatest increase. Differential scanning calorimetry studies demonstrated that trilaurin formed a 'fluid-like' core and therefore liquefied-lipid nanoparticles, which allowed dissolution of testosterone propionate in the lipid core. In contrast, tripalmitin was present in a 'solid-like' state forming solid lipid nanoparticles which did not allow testosterone propionate dissolution in the core.
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Al-Obaidi H, Lawrence MJ, Shah S, Moghul H, Al-Saden N, Bari F. Effect of drug–polymer interactions on the aqueous solubility of milled solid dispersions. Int J Pharm 2013; 446:100-5. [DOI: 10.1016/j.ijpharm.2013.02.009] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2012] [Revised: 01/31/2013] [Accepted: 02/01/2013] [Indexed: 10/27/2022]
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Dabkowska AP, Lawrence MJ, McLain SE, Lorenz CD. On the nature of hydrogen bonding between the phosphatidylcholine head group and water and dimethylsulfoxide. Chem Phys 2013. [DOI: 10.1016/j.chemphys.2012.10.016] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Welser K, Campbell F, Kudsiova L, Mohammadi A, Dawson N, Hart SL, Barlow DJ, Hailes HC, Lawrence MJ, Tabor AB. Gene Delivery Using Ternary Lipopolyplexes Incorporating Branched Cationic Peptides: The Role of Peptide Sequence and Branching. Mol Pharm 2012; 10:127-41. [DOI: 10.1021/mp300187t] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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Foglia F, Lawrence MJ, Demė B, Fragneto G, Barlow D. Neutron diffraction studies of the interaction between amphotericin B and lipid-sterol model membranes. Sci Rep 2012; 2:778. [PMID: 23110248 PMCID: PMC3482691 DOI: 10.1038/srep00778] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2012] [Accepted: 09/18/2012] [Indexed: 12/13/2022] Open
Abstract
Over the last 50 years or so, amphotericin has been widely employed in treating life-threatening systemic fungal infections. Its usefulness in the clinic, however, has always been circumscribed by its dose-limiting side-effects, and it is also now compromised by an increasing incidence of pathogen resistance. Combating these problems through development of new anti-fungal agents requires detailed knowledge of the drug's molecular mechanism, but unfortunately this is far from clear. Neutron diffraction studies of the drug's incorporation within lipid-sterol membranes have here been performed to shed light on this problem. The drug is shown to disturb the structures of both fungal and mammalian membranes, and co-localises with the membrane sterols in a manner consistent with trans-membrane pore formation. The differences seen in the membrane lipid ordering and in the distributions of the drug-ergosterol and drug-cholesterol complexes within the membranes are consistent with the drug's selectivity for fungal vs. human cells.
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Edwards S, Da-Costa-Rocha I, Lawrence MJ, Cable C, Heinrich M. A reappraisal of herbal medicinal products. NURSING TIMES 2012; 108:24-27. [PMID: 23155905] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Subscribe] [Scholar Register] [Indexed: 06/01/2023]
Abstract
Complementary and alternative medicine is increasingly popular, and encompasses a number of systems and therapies based on diverse theories and practices, such as homoeopathy, traditional herbalism, reiki, ayurvedic medicine and traditional Chinese medicine. While many are based on metaphysical concepts for which there is no sound evidence, for herbal medicines there is a rational, scientific basis and increasing clinical evidence. This article suggests herbal medicines should no longer be considered part of CAM, but instead sit alongside conventional medicines.
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Davies GR, Stanford SN, Lawrence MJ, Gill D, Williams PR, Morris K, Thomas D, Evans PA. Fractal analysis: a new biomarker for determining clot characteristics in critically ill patients. Crit Care 2012. [PMCID: PMC3363848 DOI: 10.1186/cc11037] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
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Hawkins K, Badiei N, Weisel J, Chernysh I, Williams PR, Lawrence MJ, Evans PA. Fractal dimension: a biomarker for detecting acute thromboembolic disease. Crit Care 2012. [PMCID: PMC3363849 DOI: 10.1186/cc11038] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
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Dabkowska AP, Foglia F, Lawrence MJ, Lorenz CD, McLain SE. On the solvation structure of dimethylsulfoxide/water around the phosphatidylcholine head group in solution. J Chem Phys 2011; 135:225105. [DOI: 10.1063/1.3658382] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
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Peixoto MPG, Treter J, de Resende PE, da Silveira NP, Ortega GG, Jayne Lawrence M, Dreiss CA. Wormlike micellar aggregates of saponins from Ilex paraguariensis A. St. Hil. (mate): A characterisation by cryo-TEM, rheology, light scattering and small-angle neutron scattering. J Pharm Sci 100:536–546. J Pharm Sci 2011. [DOI: 10.1002/jps.22698] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
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Kudsiova L, Fridrich B, Ho J, Mustapa MFM, Campbell F, Welser K, Keppler M, Ng T, Barlow DJ, Tabor AB, Hailes HC, Lawrence MJ. Lipopolyplex Ternary Delivery Systems Incorporating C14 Glycerol-Based Lipids. Mol Pharm 2011; 8:1831-47. [DOI: 10.1021/mp2001796] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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Dabkowska AP, Barlow DJ, Hughes AV, Campbell RA, Quinn PJ, Lawrence MJ. The effect of neutral helper lipids on the structure of cationic lipid monolayers. J R Soc Interface 2011; 9:548-61. [PMID: 21831895 DOI: 10.1098/rsif.2011.0356] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Successful drug delivery via lipid-based systems has often been aided by the incorporation of 'helper lipids'. While these neutral lipids enhance the effectiveness of cationic lipid-based delivery formulations, many questions remain about the nature of their beneficial effects. The structure of monolayers of the cationic lipid dimethyldioctadecylammonium bromide (DODAB) alone, and mixed with a neutral helper lipid, either diolelyphosphatidylethanolamine or cholesterol at a 1 : 1 molar ratio was investigated at the air-water interface using a combination of surface pressure-area isotherms, Brewster angle microscopy (BAM) and specular neutron reflectivity in combination with contrast variation. BAM studies showed that while pure DODAB and DODAB with cholesterol monolayers showed fairly homogeneous surfaces, except in the regions of phase transition, monolayers of DODAB with diolelyphosphatidylethanolamine were, in contrast, inhomogeneous exhibiting irregular bean-shaped domains throughout. Neutron reflectivity data showed that while the thickness of the DODAB monolayer increased from 17 to 24 Å as it was compressed from a surface pressure of 5-40 mN m(-1), the thickness of the helper lipid-containing monolayers, over the same range of surface pressures, was relatively invariant at between 25 and 27 Å. In addition, the monolayers containing diolelyphosphatidylethanolamine were found to be more heavily hydrated than the monolayers of cationic lipid, alone or in combination with cholesterol, with hydration levels of 18 molecules of water per molecule of lipid being recorded for the diolelyphosphatidylethanolamine-containing monolayers at a surface pressure of 30 mN m(-1) compared with only six and eight molecules of water per molecule of lipid for the pure DODAB monolayer and the cholesterol-containing DODAB monolayer, respectively.
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Foglia F, Barlow DJ, Szoka FC, Huang Z, Rogers SE, Lawrence MJ. Structural studies of the monolayers and bilayers formed by a novel cholesterol-phospholipid chimera. LANGMUIR : THE ACS JOURNAL OF SURFACES AND COLLOIDS 2011; 27:8275-8281. [PMID: 21634402 DOI: 10.1021/la200739y] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/30/2023]
Abstract
Langmuir isotherm, neutron reflectivity, and small angle neutron scattering studies have been conducted to characterize the monolayers and vesicular bilayers formed by a novel chimeric phospholipid, ChemPPC, that incorporates a cholesteryl moeity and a C-16 aliphatic chain, each covalently linked via a glycerol backbone to phosphatidylcholine. The structures of the ChemPPC monolayers and bilayers are compared against those formed from pure dipalmitoylphoshatidylcholine (DPPC) and those formed from a 60:40 mol % mixture of DPPC and cholesterol. In accord with previous findings showing that very similar macroscopic properties were exhibited by ChemPPC and 60:40 mol % DPPC/cholesterol vesicles, it is found here that the chimeric lipid and lipid/sterol mixture have very similar monolayer structures (each having a monolayer thickness of ∼26 Å), and they also form vesicles with similar lamellar structure, each having a bilayer thickness of ∼50 Å and exhibiting a repeat spacing of ∼65 Å. The interfacial area of ChemPPC, however, is around 10 Å(2) greater than that of the combined DPPC/cholesterol unit in the mixed lipid monolayer (viz., 57 ± 1 vs 46 ± 1 Å(2), at 35 mN·m(-1)), and this difference in area is attributed to the succinyl linkage which joins the ChemPPC steroid and glyceryl moieties. The larger area of the ChemPPC is reflected in a slightly thicker monolayer solvent distribution width (9.5 vs 9 Å for the DPPC/cholesterol system) and by a marginal increase in the level of lipid headgroup hydration (16 vs 13 H(2)O per lipid, at 35 mN·m(-1)).
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Groen D, Gooris GS, Barlow DJ, Lawrence MJ, van Mechelen JB, Demé B, Bouwstra JA. Disposition of ceramide in model lipid membranes determined by neutron diffraction. Biophys J 2011; 100:1481-9. [PMID: 21402030 DOI: 10.1016/j.bpj.2011.02.001] [Citation(s) in RCA: 49] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/01/2010] [Revised: 02/01/2011] [Accepted: 02/01/2011] [Indexed: 10/18/2022] Open
Abstract
The lipid matrix present in the uppermost layer of the skin, the stratum corneum, plays a crucial role in the skin barrier function. The lipids are organized into two lamellar phases. To gain more insight into the molecular organization of one of these lamellar phases, we performed neutron diffraction studies. In the diffraction pattern, five diffraction orders were observed attributed to a lamellar phase with a repeat distance of 5.4 nm. Using contrast variation, the scattering length density profile could be calculated showing a typical bilayer arrangement. To obtain information on the arrangement of ceramides in the unit cell, a mixture that included a partly deuterated ceramide was also examined. The scattering length density profile of the 5.4-nm phase containing this deuterated ceramide demonstrated a symmetric arrangement of the ceramides with interdigitating acyl chains in the center of the unit cell.
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Srijayanta S, Jones PM, Persaud S, Lawrence MJ, Raman A. In-vitro screening of medicinal plants for potential antidiabetic effects. J Pharm Pharmacol 2011. [DOI: 10.1111/j.2042-7158.1998.tb02419.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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71
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Myles AMC, Barlow DJ, France G, Lawrence MJ. A Comparison of Indomethacin/Cyclodextrin Complexes. J Pharm Pharmacol 2011. [DOI: 10.1111/j.2042-7158.1990.tb14380.x] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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72
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Rees GD, Kantaria S, Lawrence MJ. Microemulsion-based organogels: A novel matrix for transdermal drug delivery. J Pharm Pharmacol 2011. [DOI: 10.1111/j.2042-7158.1998.tb02300.x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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73
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Patel N, Marlow M, Lawrence MJ. Surface properties of fluorinated surfactants. J Pharm Pharmacol 2011. [DOI: 10.1111/j.2042-7158.1998.tb02389.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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Thomas M, Satra C, Lawrence MJ. Solubilization of testosterone propionate in oil-in-water lecithin-based microemulsions. J Pharm Pharmacol 2011. [DOI: 10.1111/j.2042-7158.1998.tb02345.x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
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