Growth and aggregation of surfactant islands during the displacement of an adsorbed protein monolayer: a Brownian dynamics simulation study

Abstract

We present Brownian dynamics simulations of the displacement of a protein monolayer by competitive adsorption. The protein film is modelled as a network of spherical bonded particles adsorbed at a fluid interface. Spherical displacer particles, which have a stronger affinity for the interface than the protein film particles, are introduced into the system through the sub-phase. At early stages, these particles diffuse to the interface and are adsorbed in the gaps in the network. Soon thereafter, however, further adsorption initiates displacement of the film particles, ultimately leading to the complete removal of the protein layer from the surface. We study the evolution of the number and size of the displacer islands formed at the interface. The introduction of a direct long-range repulsion between film and displacer particles is shown to lead to a phase-separation-type behaviour at intermediate time scales. Further comparisons with the displacement of a non-bonded monolayer are also presented.