Interactions of phospholipid monolayer with single-walled carbon nanotube wrapped by lysophospholipid

In this study, we prepared single-walled carbon nanotubes (SWNTs) wrapped by 1-stearoyl-2-hydroxy-sn-glycero-3-phospho-(1′-rac-glycerol) (LPG), leading to a complex of SWNT–LPG. In an attempt to investigate the interactions of SWNT–LPG with a mimicked cell surface, SWNT–LPG solution was injected into the sub-phase of Langmuir trough to form a mixed monolayer with dipalmitoylphosphatidylcholine (DPPC) and dipalmitoylphosphatidylglycerol (DPPG), respectively. In addition to the measurement of typical surface pressure–area isotherms under compression mode, area changes occurring during insertion of SWNT–LPG into the monolayer were recorded at various surface pressures. Changes in surface potential were also measured for evident tracing of the degree of interactions between sub-phase and monolayer. A systematic comparison of relaxation patterns and insertion behavior along with surface potential data provided a rational basis to distinguish the degree of interactions between SWNT–LPG and the designated monolayer. The observed tendencies were found to be in accordance with the surface topography as revealed by the tapping mode atomic force microscopy. It was consistently observed that SWNT–LPG interacted with DPPC to a greater extent than with DPPG, when the sufficient coverage of nanotube surface by LPG molecules was assured.

► Complex of single-walled carbon nanotubes and lysophospholipid (SWNT-LPG) is formed.
► Composite monolayer is formed by inserting SWNT-LPG into the phospholipid monolayer.
► We measure area-pressure responses and dipole potentials during the insertion process.
► Properties of composite monolayer depend on the kind of phospholipid and LPG content.