Scanning electrochemical microscopy of living cells. 5. Imaging of fields of normal and metastatic human breast cells

Scanning electrochemical microscopy (SECM) was used to image fields of different types of human breast cells in monolayer culture. The goal of these experiments was to demonstrate the possibility of distinguishing between nontransformed human breast epithelial cells (MCF-10A) and metastatic breast cells (MDA-MB-231) by their redox activities. Imaging of densely packed cells by SECM requires approaches that differ from previously reported experiments with well-separated single cells. The combination of SECM with optical and fluorescence microscopies was used to locate individual cells in a homogeneous or heterogeneous field of cells. To establish that metastatic breast cells can be detected against a field of normal cells, the former were preloaded with fluorescent nanospheres and plated together with unlabeled MCF-10A cells. By matching SECM and fluorescence images of a selected group of metastatic cells, the level of discrimination and fidelity of the SECM signal could be shown. Several factors (distance between the electrode and the cells, cell density, choice of mediator, and its concentration) were identified that can be used to maximize the contrast between images of metastatic and nontransformed cells. These studies provide a framework for future analysis of malignant cells in human breast tissue samples.