Charge Displacement by Adhesion and Spreading of a Cell:  Amperometric Signals of Living Cells

In Situ Amperometric Characterization of Liposome Suspensions with Concomitant Oxygen Reduction

“…Furthermore, the final area of the contact interface of liposome is 5 times smaller than the area of the contact interface of D. tertiolecta cell. The area of the contact interface formed by adhesion of D. tertiolecta cells exceeded up to 100 times the cross-section area of a free cell [7]. This demonstrates larger contribution of cell content to the final area of the contact interface of D. tertiolecta cells, which is missing in the case of rupture and spreading of liposome, filled with aqueous electrolyte solution.…”

“…that the signal amplitudes of liposomes were larger than the signal amplitudes of cells, the individual adhesion events of liposomes did not result in a measurable decrease of oxygen reduction current, i.e., in the increase of surface coverage of the electrode, which is in line with the fact that liposome interior is PBS only. On the other hand, adhesion signals of D. tertiolecta cell are followed by a decrease in oxygen reduction current due to the release of cell surface-active constituents after cell rupture [7]. After 24 adhesion signals of D. tertiolecta cells, oxygen reduction current at the end of drop-life (time of 2 s) falls to a diffusion-controlled value.…”

“…D. tertiolecta cell suspension in 0.1 M aqueous electrolyte solution represents a well-studied model system [7,24] suitable for electrochemical detection due to the cell-size and membrane properties. Cell-growth and separation procedures were described in reference [7].…”

“…Idt [4,7]. If we assume that complete charge displacement takes place, as in the case of oil droplets [4], the area of the contact interface, A c , is determined from the amount of displaced charge, or amperometrically (signal amplitude !…”

“…By potentiostatic control of surface charge and tension, adhesion forces can be fine tuned to study the interplay of complex forces involved in surfaceactive particles (vesicles, microdroplets and cells)/electrode double-layer interactions [4,5]. During their attachment and spreading at the charged interface, surface-active particles displace the double-layer charge from the inner Helmholtz plane, and the transient flow of compensating current can be recorded as an electrical adhesion signal [4,6,7]. After the studies of adhesion signals of non-polar hydrocarbon droplets and of negatively charged living cells [7 -10] we focused here on lipid vesicles (liposomes), the classical model for studying physical mechanisms of cell adhesion [11].…”