engleski

Charge displacement by adhesion and spreading of a cell:Amperometric signals of living cells

The aim of the present work is to trace adhesion response of single particles without influence of electron redox-exchange at the electrode. We have studied amperometric response of single cell adhesion in real time, from the initial attachment to a finite state of spread cell at the growing mercury drop electrode. The technique is based on measurement of double-layer charge displacement. The only hypothesis used in interpreting the signals is the validity of the electrical double-layer model. The flow of compensating current reflects the dynamics of adhesive contact formation and subsequent spreading of a cell. The rate of adhesion and spreading of cells is enhanced by the hydrodynamic regime of electrode’s growing fluid interface. The spike-shaped signals have the peak current in ľA range, duration of 5-10 ms and displaced charge in nC range. The electrochemical technique thus allows a precise measurement of the contact area between the cell and the electrode. The distance of the closest approach of an adhered cell can be estimated with certainty as equal or smaller than the outer Helmholtz plane i.e. 0.3-0.5 nm. There is clear evidence of cell rupture in the potential range of maximum attractive interaction, which is around the potential of zero charge. A surprising similarity to adhesion signals of droplets of liquid hydrocarbons (C12 – C18) suggest that collective properties of cell exterior govern the dynamics of adhesion and rate of spreading, with fluidity playing a major role. Our results demonstrate a general significance of adhesion phenomena in single particle - electrode interaction. When electroactive molecules reside in an organized microenvironment, such as colloidal particles, microdroplets or vesicles, their redox reaction at the electrode is preceded by adhesion step that is likely to become rate-determining.

amperometric signals; algal cells; dropping mercury electrode

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