Low concentrations of negatively charged sub-micron particles alter the microstructure of DPPC at the air–water interface

The function of dipalmitoyl phosphatidylcholine (DPPC) Langmuir monolayers was studied after exposure to various concentrations of 200 nm carboxyl-modified polystyrene particles by a combination of surface pressure and surfactant microstructure studies. The presence of particles in the subphase at the lowest concentrations tested (10−5 to 10−4 g/L) did not influence the π–A isotherms. However, at the highest concentration (10−3 g/L), changes in the hysteresis areas of the isotherms were observed. The formation of LC domains during compression was significantly altered by the presence of the particles, resulting in the formation of smaller but more numerous domains. Fluorescence and atomic force microscopy images suggested that particles remained in the subphase but were closely associated with the condensed domains.

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► Negatively charged polystyrene particles did not alter DPPC monolayer collapse.
► Particles increased the hysteresis area of DPPC surface pressure isotherm during cycling.
► Particles resulted in smaller but more numerous condensed DPPC domains.
► Particles were associated with the condensed DPPC domains.