Scanning electrochemical microscopy of HeLa cells – Effects of ferrocene methanol and silver ion

The viability and activity of HeLa cells were probed using scanning electrochemical microscopy (SECM). The feedback generated by HeLa cells during scanning depends on the electrochemical mediator. Living HeLa cells generated positive feedback when ferrocene methanol (FcMeOH) was oxidized at the tip, showing that the cells reduced FcMeOH+. The positive feedback with FcMeOH changed to negative feedback when the HeLa cells were exposed to toxic treatments, i.e. CN− or UVC radiation, suggesting that FcMeOH+ reduction can be used to monitor cell activity. Living HeLa cells also accumulate FcMeOH after exposure times of a few h, but the presence of mM concentrations of FcMeOH has no apparent effect on the cell viability. The effect of Ag+ (known to be toxic to bacteria at the 10 μM level) on HeLa cells was probed using the FcMeOH as an indicator. The activity of the HeLa cells was not affected in a culture medium containing Ag+ up to 10 mM. The uptake of Ag+ by living and dead HeLa cells was small and nearly the same, indicating that even at high Ag+ concentrations in the culture medium, only a small amount of Ag+ is accumulated within the cells.