title: Measuring the lamellarity of giant lipid vesicles with differential interference contrast microscopy.
abstract: Giant unilamellar vesicles are a widely utilized model membrane system, providing free-standing bilayers unaffected by support-induced artifacts. To measure the lamellarity of such vesicles, fluorescence microscopy is one commonly utilized technique, but it has the inherent disadvantages of requiring lipid staining, thereby affecting the intrinsic physical and chemical properties of the vesicles, and it requires a calibration by statistical analysis of a vesicle ensemble. Herein we present what we believe to be a novel label-free optical method to determine the lamellarity of giant vesicles based on quantitative differential interference contrast (qDIC) microscopy. The method is validated by comparison with fluorescence microscopy on a statistically significant number of vesicles, showing correlated quantization of the lamellarity. Importantly, qDIC requires neither sample-dependent calibration nor sample staining, and thus can measure the lamellarity of any giant vesicle without additional preparation or interference with subsequent investigations. Furthermore, qDIC requires only a microscope equipped with differential interference contrast and a digital camera.
authors.affiliation: School of Biosciences and School of Physics and Astronomy, Cardiff University, Cardiff, United Kingdom.
authors.forename: C I
authors.initials: CI
authors.lastname: McPhee
authors.forename: G
authors.initials: G
authors.lastname: Zoriniants
authors.forename: W
authors.initials: W
authors.lastname: Langbein
authors.forename: P
authors.initials: P
authors.lastname: Borri
mesh_terms: D008858:Microscopy, Phase-Contrast; D013050:Spectrometry, Fluorescence; D053835:Unilamellar Liposomes / Q000737:chemistry*
chemical_list: D053835:Unilamellar Liposomes
references.citation: Chemphyschem. 2007 Apr 23;8(6):834-48
references.pmid: 17394281
references.citation: J Biophotonics. 2014 Jan;7(1-2):68-76
references.pmid: 23193020
references.citation: Acta Biochim Pol. 2009;56(1):33-9
references.pmid: 19287805
references.citation: Anal Chem. 2008 May 15;80(10):3666-76
references.pmid: 18422336
references.citation: Lab Chip. 2013 Mar 7;13(5):752-67
references.pmid: 23291662
references.citation: Curr Opin Chem Biol. 2007 Dec;11(6):581-7
references.pmid: 17976391
references.citation: Biophys J. 1984 May;45(5):891-9
references.pmid: 6733240
references.citation: Biophys J. 2001 Mar;80(3):1417-28
references.pmid: 11222302
references.citation: Biophys J. 1996 Dec;71(6):3242-50
references.pmid: 8968594
references.citation: Biophys J. 1990 Jun;57(6):1179-86
references.pmid: 2393703
references.citation: Chemphyschem. 2007 Oct 22;8(15):2156-70
references.pmid: 17768730