Development of the Scanning Electrochemical Microscope for Biological Imaging

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AbstractDEVELOPMENT OF THE SCANNING ELECTROCHEMICAL MICROSCOPE FOR BIOLOGICAL IMAGINGThe scanning electrochemical microscope (SECM) is a scanned-probe microscope with the unique ability to image both the topography and chemistry of a surface. The SECM has been used primarily to examine inanimate objects but, with its potential for monitoring chemical secretion and examining morphology, holds great promise in biological investigations. Indeed, the BioSECM will be used to image the topography and probe the chemistry of living cells.A team of two chemists and a biologist will join forces to develop a new scanning electrochemical microscope for use with biological samples. The new BioSECM will have a combination of features not found in other existing microscopes. Its role is to construct 3-d images of the surfaces of living cells while simultaneously producing sensitive maps and time-resolved analysis of selected chemical processes at the surface of the cells. Unique to this scanning microscope is the ability to observe features as large as 1000 , 1000 , 20 mm (l , w, h) with lateral resolution below 1 mm and to correlate topographic and chemical images for detection of morphological changes accompanying changes in cell secretion. The microscope will incorporate features not available in commercial instruments such as the ability to image surfaces at constant-separation by use of shear-force or impedance mode feedback controllers and the ability to acquire chemical information by employing voltammetric, amperometric, or potentiometric tips. Probes will be developed that are suitable for amperometric and voltammetric detection of biologically important molecules released from sample surfaces. The utility of the BioSECM is minimized if use of an imaging probe perturbs or destroys a living sample. Thus, imaging methods will be developed to avoid damage to samples. Alternately, the probe can be used to intentionally alter or destroy biological structures by transiently generating toxic chemicals near sample surfaces. The ability of the BioSECM to image living cells will be tested by using it to examine PC12 cells, a cell line used to model many aspects of neuron function.The BioSECM will advance biological investigations of cultured living cells. In the near term, the BioSECM will be an invaluable tool for investigations into nerve cell growth and death by allowing changes in morphology and neurotransmitter release to be simultaneously monitored. Additionally, the BioSECM will be useful in many other biologically relevant areas. For example, metallic corrosion investigations will be furthered by the ability to examine biologically induced corrosion processes and biofilms on medical and dental implants. BioSECM will also be an invaluable tool for investigations into neuron degeneration, as changes in cell morphology and chemical environment can be simultaneously measured. Moreover, it is felt that the SECM imaging community at large will appreciate the technological advances of the BioSECM and it is anticipated that other investigators will build one or be the basis of a commercial device.