Investigation of the interactions between silver nanoparticles and Hela cells by scanning electrochemical microscopy‡

The interactions between Hela cells and silver nanoparticles (AgNPs) have been studied by scanning electrochemical microscopy (SECM) with both IrCl62−/3− and Fe(CN)63−/4− as the dual mediators. IrCl62−, which can be produced in situ and react with AgNPs, is used as the mediator between the AgNPs on the cells and the SECM tip. Another redox couple, Fe(CN)63−/4−, which has a similar hydrophilicity to IrCl62−/3−, but cannot react with AgNPs, is also employed for the contrast experiments. The cell array is cultured successfully onto a Petri dish by microcontact printing (μCP) technique, which can provide a basic platform for studying of single cells. The approach curve and line scan are the two methods of SECM employed here to study the Hela cells. The former can provide the information about the interaction between Hela cells and AgNPs whereas the later gives the cell imaging. The permeability of cell membranes and morphology are two main factors which have effects on the feedback mode signals when K3Fe(CN)6 is used as the mediator. The permeability of the cell membranes can be ignored after interaction with high concentration of AgNP solution and the height of the Hela cells is slightly decreased in this process. The kinetic rate constants (k0) between IrCl62− and Ag on the Hela cell can be evaluated using K3IrCl6 as the mediator, and they are increased with the higher concentrations of the AgNP solutions. The k0 is changed about 10 times from 0.43 ± 0.04 × 10−4 to 1.25 ± 0.07 × 10−4 and to 3.93 ± 1.9 × 10−4 cm s−1 corresponding to 0, 1 and 5 mM of AgNO3 solution. The experimental results demonstrate that the AgNPs can be adsorbed on the cell surface and detected by SECM. Thus, the amount of AgNPs adsorbed on cell membranes and the permeability or morphology changes can be investigated simultaneously using this approach. The dual mediator system and cell array fabricated by μCP technique can provide better reproducibility because they can simplify experiments, and provide a platform for further single cell detection.