Tracking live cell response to cadmium (II) concentrations by scanning electrochemical microscopy

The biological chemistry of toxic heavy metals, such as Cd (II), has become an active area of research due to connections with increased oxidative stress, cytotoxicity, and human/animal carcinogenicity. In this study, scanning electrochemical microscopy (SECM) was used as a noninvasive technique to monitor membrane permeability of single live human bladder cancer cells (T24) subjected to exposure of Cd (II) at various concentrations. The addition of a membrane permeable redox mediator, ferrocenemethanol (FcMeOH), in combination with depth scan imaging provided probe approach curves (PACs) to reveal changes in membrane homeostasis. To demonstrate the strength of SECM as a bioanalytical technique for cell physiology and pathology, we tested responses of live cells after 1h incubations with various concentrations of Cd (II). For the first time, a trend in membrane permeability of Cd (II) treated live T24 cells was discovered. Dependent on the incubation concentration, the trend displayed an initial decrease in membrane permeability coefficient from 75μm/s for control cells to 25μm/s for cells incubated with 75μM Cd (II). This was followed by an eventual return to the permeability coefficient of control cells (75μm/s) with further increases in Cd (II) exposure. The cells were found to respond at as little as 10μM Cd (II) concentrations. This work further demonstrates the use of SECM as a bioanalytical technique to monitor cell physiology and topography. A greater insight into the complex mechanisms behind Cd (II) toxicity is anticipated.