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This article describes a novel electrochemical technique for the real-time monitoring of changes in the behaviour of adherent human cells in vitro: i.e., a biosensor that combines a biological recognition mechanism with a physical transduction technique, described collectively as Oncoprobe. Confluent viable cells adherent to gold electrodes (sensors) modify the extracellular microenvironment at the cell:sensor interface to produce a change in the electrochemical potential compared to that measured in the absence of cells. The potential was measured as an open circuit potential (OCP) with respect to a saturated calomel reference in the bulk culture medium. Typical OCP values for confluent cultures of human breast carcinoma cells, 8701-BC, approximated -100 mV compared with cell-free values of approximately -15 mV. The OCP for 8701-BC cells was modified in response to temperature changes over the range 32 to 40 degrees C and also to treatments with phytohemagglutinin (PHA, 25 microg/mL), cycloheximide (30 microM) and interleukin-1 beta (IL-1, 0.5 ng/mL) over 24 h. Cultures of synovial fibroblasts also responded to the same treatments with similar responses, producing negative shifts in the OCP signal with PHA and IL-I, but a positive shift in OCP signal with cycloheximide, all relative to the untreated control cultures. From experimental data and theoretical considerations it is proposed that the cell-derived signals are mixed electrode potentials reflecting a "conditioned," more reducing environment at the cell:sensor interface. Only viable cells caused a negative shift in the OCP signal, this being lost when cells were rendered nonviable by formalin exposure. This technology appears unique in its ability to passively "listen in" on cell surface activities, suggesting numerous applications in the fields of drug discovery, chemotherapy, and cell behaviour.

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The anodic behavior of zinc has been studied in sulfamic acid‐formamide solutions as a function of sulfamic acid concentration, temperature, and water content of solutions. It has been shown that anodic polarization curves for Zn are typical of polishing systems, and it has been found that linear relationships exist between limiting current densities and the reciprocal viscosities of the solutions. The processes in solution are controlled by diffusion of cations or of solvent species. Film formation occurs at the onset of polishing as shown by a‐c impedance studies, and this film is either highly soluble or unstable in the presence of considerable amounts of water. The over‐all conclusion is that the mechanisms of polishing in sulfamic acid‐formamide solutions are in agreement with those proposed by Hoar for anodic polishing in other environments.

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