engleski

Probing Polymer Adsorption by Cell Adhesion at an Electrified Aqueous Interface

Unicellular marine algae Dunaliella tertiolecta (cell diameter 6-9 µ m) can be characterized through their adhesion at mercury electrode that results in well-defined adhesion signals at millisecond time scale, both at dropping and static mercury electrodes. It was previously shown that the frequency of adhesion signals depends on biopolymer surface concentration. For the given cell density frequency of cell adhesion decreases with the increase in surface coverage of dextran molecules. In this study, we want to show that the existence and the extent of polymer adsorption at the charged mercury electrode/electrolyte interface can be probed by cell adhesion. Nonpolar dextran and negatively charged dextran sulfate sodium salt, both of average molecular weight 500 000, were used as models of dissolved biopolymers. Dextrans are known for their specific adsorption (displacement of water molecules and ions) at mercury electrode/aqueous solution interface in a range of positive but also negative surface charges. Adsorption of dextran molecules is fast and controlled by mass transport from the solution. The competition between polymer adsorption and cell adhesion was studied at the positively (σ Hg = +3.8 µ C cm-2) and negatively (σ Hg = -6.5 µ C cm-2) charged static mercury drop electrode/0.1M NaCl solution interface using electrochemical technique – chronoamperometry. As expected, the frequency of cell adhesion signals decreases significantly at positively and negatively charged mercury electrode upon the addition of nonpolar dextran. In contrast, the frequency of adhesion signals of Dunaliella tertiolecta cells decreases significantly with the addition of dextran sulfate only at the positively charged mercury electrode/electrolyte interface. Obtained results provide clear evidence for the electrostatic repulsion between dextran sulfate molecules and negatively charged mercury electrode since the frequency of adhesion signals is not affected by the addition of dextran sulfate up to the concentration of 150 mg L-1.

adsorption of biopolymers; cell adhesion; mercury electrode; dextran sulfate adsorption

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