Amphiphilic dicationic surfactants, known as gemini surfactants, are currently studied for gene delivery purposes. The gemini surfactant molecule is composed of two hydrophilic “head” groups attached to hydrophobic chains and connected via molecular linker between them. The influence of different concentrations of 1,5-bis (1-imidazolilo-3- decyloxymethyl) pentane chloride (gemini surfactant) on the thermotropic phase behaviour of 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) bilayers with and without the presence of DNA was investigated using Fourier transformed infrared (FTIR) and circular dichroism (CD) spectroscopies, small angle scattering of synchrotron radiation and differential scanning calorimetry. With increasing concentration of surfactant in DMPC/DNA systems, a disappearance of pretransition and a decrease in the main phase transition enthalpy and temperature were observed. The increasing intensity of diffraction peaks as a function of surfactant concentration also clearly shows the ability of the surfactant to promote the organisation of lipid bilayers in the multilayer lamellar phase.

The phospholipidgemini surfactant systems are promising agents for construction of lipoplexes for DNA delivery systems in gene therapy. In this work the inuence of a gemini surfactant 1,1 ′ -(1,6-hexan)bis3-octyloxymethylimidazolium di-chloride) (IMI_Cl_C6_C8) on the structure and phase behaviour of aqueous suspensions of the fully hydrated phospholipid 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC) were characterised using small angle scattering of synchrotron radiation (SAXS), dierential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR). The surfactant studied caused a destabilisation of the lamellar phase typical of DPPC. Addition of the surfactant also shifted to lower temperatures and extended the range of the main phase transition