Polylysine induces changes in membrane electrical properties of K562 cells

The ionic environment of the cell membrane is of extreme importance in maintaining cell integrity and the numerous functions necessary for cell growth, differentiation, etc., as well as in cell-biomaterial interactions. In this study, the effects of polylysine (a basic poly-amino acid with a net positive charge which is often used to coat biomaterials surfaces) on the erythroleukemic K562 cell membrane were investigated. In particular, the effects of this polycation were evaluated using dielectric relaxation studies in the radiofrequency range with which it is possible to measure both active ionic transport across the cell membrane (membrane conductivity) and the static charge distribution present on the cell surface due to the structural components of the cell membrane (membrane permittivity). The conductivity of the cytosol can also be determined. The results demonstrate that while the conductivity of the cytosol is not significantly altered, both the conductivity and permittivity of the K562 cell membrane are varied by exposure of these cells to polylysine. These observations indicate that both active ionic transport and the type, quantity, or distribution of membrane components such as lipids, proteins, and polysaccharides may also be altered. Although the precise mechanisms by which these variations in K562 cells occur are unknown, it can be hypothesized that changes in the growth characteristics of these cells may be in part responsible. In particular, as demonstrated by light microscopic examination of K562 cells directly in the culture flasks, the cells in polylysine-coated flasks do not grow in suspension as do the controls, but rather show anchorage-dependent-like behavior. It is this important change from suspension to monolayer growth induced by polylysine that may be responsible for the changes in membrane electrical parameters.