Scanning electrochemical microscopy: detection of human breast cancer cells by redox environment.

Scanning electrochemical microscopy (SECM) can be used to measure the redox activity of individual human breast cells. A chemical mediator (e.g. quinone) that rapidly crosses the membrane participates in intracellular redox reactions that are recorded on a microsecond timescale by an ultramicroelectrode positioned close to the membrane. Measurements of redox reactivity yield rate constants that are different for cancerous and non-transformed human breast cells. With non-transformed or metastatic cells, rate constants are modulated by altered expression or activity of protein kinase Calpha, an enzyme involved in the mechanism of cell metastasis. When used in two-dimensional scanning, SECM produces a spatially resolved redox map of an individual cell or field of cells and can detect individual breast cancer cells in a field of non-transformed cells. These studies identify a new technology for cancer detection and establish a framework for future analysis of malignant cells in human breast tissues and biopsies.