Carbon Nanodiamond Induced Alterations in Phospholipid Domain Formation Depends on Lipid Saturation and Headgroup Charge

Carbon nanodiamonds are being increasingly used in several applications including energy generation and drug delivery applications. While these engineered carbon nanodiamonds (ECNs) often come in contact with biological membranes, their interactions with these systems is not understood. We describe concentration and time dependent alterations in the lipid domain formation in four phospholipid films at the air/water interface that serve as model biomembranes. We find that ECNs induce a alteration in pure saturated dipalmytolphosphatdylcholine (DPPC) films as well as a mixture of DPPC with and unsaturated lipid POPC (7:3). However, a mixture of DPPC and 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphatidylglygerol(POPG) or saturated dipalmytolphosphatidylglygerol DPPG (7:3) does not show any alterations in the lipid domain formation. These results suggest that ECNs have a tendency to alter the line tension and dipole density distribution in lipids, which in turn explains the observed differences in the lipid domain structures.