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.
News published in Agência FAPESP Newsletter about the scholarship: