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Structural characterization of cationic amphiphilic aggregates: a study with the fluorescent probe Laurdan

Grant number: 13/24949-0
Support Opportunities:Scholarships in Brazil - Scientific Initiation
Effective date (Start): January 01, 2014
Effective date (End): May 22, 2015
Field of knowledge:Physical Sciences and Mathematics - Physics - Condensed Matter Physics
Principal Investigator:Maria Teresa Moura Lamy
Grantee:Marcos Kunihiro Masukawa
Host Institution: Instituto de Física (IF). Universidade de São Paulo (USP). São Paulo , SP, Brazil
Associated scholarship(s):14/14682-9 - Mechanics and functionality of the cell interface studied by model systems, BE.EP.IC


The work to be developed by the student Marcos Kunihiro Masukawa is part of a broader project of the Biophysics Group of the Institute of Physics, University of São Paulo, which aims to characterize the structure of amphiphilic aggregates in aqueous solution (FAPESP 2013/14419-3). Particularly, the study of cationic amphiphiles is the topic studied by the post-doctor Dr. Julio H.K. Rozenfeld (FAPESP 2011/13079-9), in collaboration with the laboratory specialist Dr. Evandro L. Duarte, and researchers of the biological field, interested in the pharmacological use of lipid complexes. We propose the study of vesicles of the amphiphilic DODAB (Dioctadecyldimethylammonium bromide), which has a quaternary ammonium at the headgroup. Due to the positive charge of this group, nucleotides, oligonucleotides and DNA associate to the bilayer. We want to characterize pure and associated vesicles, and, for comparison, study the effect of the addition of ions to the medium, which will be responsible for head-group electrostatic shielding. The main techniques to be employed are steady state fluorescence and time-resolved fluorescence, using Laurdan as a probe incorporated into DODAB aggregates. We aim at a better understanding of the superficial structure of these cationic bilayers, comparing with the characteristics of the probe in neutral and anionic lipid vesicles. We expect to understand more about the structure of lipoplexes, which are used in gene therapy. Moreover, we intend to widen our knowledge about the properties of the probe Laurdan, studying its spectroscopic characteristics in cationic bilayers. Auxiliary techniques shall be employed, and studied, to characterize pure and associated vesicles: differential scanning calorimetry (DSC), dynamic light scattering (DLS) and surface potential measurements (zeta-potential). This project will be developed in collaboration with Dr. Evandro L. Duarte.

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Scientific publications
(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)
MASUKAWA, MARCOS K.; VEQUI-SUPLICY, CINTIA C.; DUARTE, EVANDRO L.; LAMY, M. TERESA. A closer look into laurdan as a probe to monitor cationic DODAB bilayers. JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY A-CHEMISTRY, v. 376, p. 238-246, . (13/24949-0, 10/08365-0, 13/14419-3)

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