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.

Self-assembly of C60 molecules on planar n-or p-type Si(100) has been accomplished by direct tethering onto the Si surface without using any intermediate functional hydrocarbon chain. Photoresponse has been observed on these monolayer modified electrodes in both aqueous and nonaqueous media. The p-type Si(100) surface with a bound C60 monolayer is also capable of mediating redox reactions. These C60 monolayer modified Si electrodes are very stable in both acidic aqueous and polar nonaqueous solvents. Characterization by fast atom bombardment mass spectroscopy (FAB-MS) suggests that simultaneous hydrosilylation and hydrogenation reactions account for the nature of the monolayer formation.

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Electrochemical studies of the products of C60 γ-irradiated in cyclohexane were conducted using the frequency response of hydrodynamic modulation at rotating disk electrodes (HMRDE) to determine transport properties by a methodology independent of the concentration of the electroactive species. The diffusion coefficients of C60 and its γ-irradiated product were separately determined to be 1.9 × 10-6 and 0.96 × 10-6 cm2/s, respectively, at 50 °C. The estimated Stokes radius of the radiolytic product of C60 approaches twice that of the fullerene itself. Such a result for γ-radiolysis in cyclohexane solution is consistent with the formation of cyclohexane adducts and likely some C60 dimer.

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