Dr Sajal Kumar Ghosh, Assistant Professor, Department of Physics and his Ph.D. student, Ms. Saheli Mitra, have recently published a paper in Langmuir (2020), 36, 328- 339, titled: “Surface activities of a lipid-analogue room temperature ionic liquid and its effects on phospholipid membrane”.
The exceptional physicochemical and tunable properties of room temperature ionic liquids (RTILs) extend their fields of potential applications even in pharmaceutical industry, bio-membrane, drug delivery and bio nano-technology along with polymer synthesis, food processing and energy harvesting industries. Moreover, several recent studies have shown the ILs to inhibit the growth of bacteria exhibiting antibacterial activity. Among various RTILs, imidazolium-based ILs are found to be very effective in developing antimicrobial and antifungal drugs. Some recent studies have shown that in comparison with the 1-alkylated imidazolium salt, 4, 5-alkyl-N-heterocyclic imidazolium salts (lipid analogues with two chains) exhibit many fold stronger anti-tumor activities in C6 glioma cell lines. So, there are great efforts of synthesizing these di-alkylated imidazolium-based ionic liquids (ILs) for developing new antibiotics. In the present study, the lipid analogue (LA) molecule MeIm(COOH)Me(Oleylamine)Iodide has been synthesized and its surface activities along with the effectiveness in restructuring of a model cellular membrane have been quantified. The molecule is found to be highly surface active as estimated from area-pressure isotherm of a monolayer of the molecules formed at air-water interface. The x-ray reflectivity (XRR) studies of a monolayer dip-coated on a hydrophilic substrate have shown the structural properties of the layer which resembles to unsaturated phospholipids. The LA molecules are observed to fluidize a phospholipid bilayer formed by the saturated lipid 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC). At lower surface pressure, the lipid monolayer of DPPC has exhibited a thickening effect at a low concentration of added LA and a thinning effect at higher concentration. However, at high surface pressure of the monolayer, the thickness is found to decrease monotonically. The in-plane pressure dependent interaction of LA molecules with model cellular membrane and corresponding perturbation in the structure and physical properties of the membrane may be linked to the strong lysing effect of these type of molecules.