Characterization of Monoolein-Based Lipoplexes Using Fluorescence Spectroscopy |
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Authors: | J P Neves Silva P J G Coutinho M E C D Real Oliveira |
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Institution: | (1) Physics Department, University of Minho, Campus of Gualtar, 4710-057 Braga, Portugal |
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Abstract: | Lipoplexes are commonly used as delivery systems in vitro and in vivo, the role of a neutral lipid as helper being of extreme importance in these systems. Cationic liposomes composed of dioctadecyldimethylammonium
bromide (DODAB) with monoolein (MO) as a helper, at different molar ratios (1:2; 1:1 and 1:0.5) were prepared, and subsequently
titrated to DNA. The structural and physicochemical properties of the lipid/DNA complexes were assessed by ethidium bromide
(EtBr) exclusion, 90° static light scattering (90° SLS) assays and fluorescence resonance energy transfer (FRET). In EtBr
exclusion assays, the steady-state fluorescence spectra of EtBr were decomposed into the sum of two lognormal emissions, emanating
from two different environments – H2O and DNA, and the effect of charge ratio (+/-) was observed. 90° SLS assays gave an important contribution, detecting size
variations in systems with different MO fractions on the lipoplexes. In FRET assays, 2-(3-(diphenylhexatrienyl)propanoyl)-1-hexadecanoyl-sn-glycero-3-phosphocholine
(DPH-HPC) was used as donor and EtBr as acceptor. The DNA component previously calculated by EtBr exclusion, was used to determine
the energy transfer efficiency, as an indirect measurement of the lipoplexes structural and physicochemical properties. Our
results demonstrate that the inclusion of monoolein in the cationic liposomes formulation significantly modifies the rate
of DNA complexation, being DODAB:MO (1:1) the system with higher DNA condensation efficiency. |
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Keywords: | Monoolein-based lipoplexes EtBr exclusion FRET 90° SLS |
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