Cationic liposomes/DNA (lipoplexes) have been widely used as non-viral vectors for
transfection, the role of the neutral lipid in liposome formulation being determinant for the
efficiency of this process [1,2]. In this work, we studied the potential of monoolein (MO)
as helper lipid for cellular transfection. Lipoplexes composed of pDNA and
dioctadecyldimethylammonium bromide (DODAB)/1-monooleoyl-rac-glycerol (MO) at
different molar ratios (4:1, 2:1 and 1:1) were investigated, as well as different cationic
lipid/DNA ratios. The physicochemical properties of the lipoplexes (size and charge), the
formation of the lipoplexes, the effect of MO on pDNA condensation and the effect of
heparin on percentage of pDNA release from the lipoplexes were also studied by
Ethidium Bromide (EtBr) exclusion assays, Dynamic Light Scattering (DLS), Zeta
Potential (æ) and electrophoresis. The cytotoxicity, transfection efficiency, as well as the
intracellular localization of labeled DNA were evaluated on 293T cells. It was found that
the presence of MO not only increases the efficiency of pDNA compactation, but also
affects the physicochemical properties of lipoplexes, which could possibly interfere with
lipoplex-cell interactions. The DODAB:MO (2:1) and (4:1) formulations were capable of
efficiently mediate in vitro cell transfection. These results were consistent with
fluorescence microscopy studies, which illustrated that lipoplexes were able to gain entry
into the cytosol and deliver pDNA to the nucleus. Understanding the structure–activity
relationship of MO based lipoplexes will give direction toward the development of safe
and efficient gene delivery systems.Portuguese Foundation for Science and Technology (FCT) for financial support to Center of
Physics and Center of Molecular & Environmental Biology and funding through projects PTDC/QUI/69795/2006 and SFRH/BD/46968/2009
