Nanorheology of poly - and monodispersed polymer brushes under oscillatory flow as models of epithelial cancerous and healthy cell brushes

In this work we study the rheology of polymeric brushes at the nanoscale interacting with an explicitly included atomic force microscopy (AFM) tip, using dissipative particle dynamics simulations, as models for pericellular brushes on epithelial cells. Two types of cells brushes are modeled: normal cells, whose surface is covered by brushes of uniform length, and cancer cells, which are covered by brushes of non-uniform length. To study their rheology, an external oscillatory shear acting on the surface of the model cells is applied, at two values of stiffness of the chains that conform the brushes. Properties such as viscosity, the coefficient of friction and interfacial tension are reported as profiles along the direction normal to the surface of the cell and are found to depend on the amplitude of the external oscillatory shear. Additionally, it was found that the mean thickness of the brush decreases with increasing amplitude of the external motion. Moreover, it is noteworthy that the properties of the uniform brush are qualitatively different from those of the polydispersed one when the oscillatory shear acts on the sample. It is argued that these differences arise from the collective effect of the chains that conform the brushes. These results illustrate the usefulness of applying physical methods such as AFM in studies of diagnosis and characterization of cancer cells. (C) 2017 Elsevier Ltd. All rights reserved.