Effect of intra-membrane C-60 fullerenes on the modulus of elasticity and the mechanical resistance of gel and fluid lipid bilayers

Penetration and partition of C-60 to the lipid bilayer core are both relevant to C60 toxicity, and useful to realise C-60 biomedical potential. A key aspect is the effect of C-60 on bilayer mechanical properties. Here, we present an experimental study on the mechanical effect of the incorporation of C-60 into the hydrophobic core of fluid and gel phase zwitterionic phosphatidylcholine (PC) lipid bilayers. We demonstrate its incorporation inside the hydrophobic lipid core and the effect on the packing of the lipids and the vesicle size using a combination of infrared (IR) spectroscopy, atomic force microscopy (AFM) and laser light scattering. Using AFM we measured the Young's modulus of elasticity (E) of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC), 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) and 1,2-distearoyl-snglycero-3-phosphocholine (DSPC) in the absence (presence) of intra-membranous C-60 at 24.5 degrees C. E of fluid phase supported bilayers is not altered by C-60, but E increases with incorporation of C-60 in gel phase bilayers. The increase is higher for longer hydrocarbon chains: 1.6 times for DPPC and 2 times for DSPC. However the mechanical resistance of gel phase bilayers of curved bilayered structures decreases with the incorporation of C-60. Our combined results indicate that C-60 causes a decrease in gel phase lipid mobility, i.e. an increase in membrane viscosityChinese Scholarship Council; Oxford Martin SchoolSCI(E)EIARTICLEs.antoranzcontera1@physics.ox.ac.uk4017102-17108