Cell Pairs Information Scanning Electrochemical Microscopy Imaging Studies

In the preface, first of all, the basic apparatus, the operation modes of scanning electrochemical microscopy (SECM) were introduced briefly. Then, the tips in SECM including ultramicroelectrode (UME), dual electrode, chemical modified electrodes, ionic selected microelectrode (ISME) etc, and the applications of SECM in the investigation for cells and enzyme were reviewed.In the first part, dual-Au electrodes were fabricated and characterized, compared with single electrode. There is no marked difference between them. Then approach curves for the dual-Au electrodes over both insulating and conductive substrates were obtained numerically. By fitting an experimental current/distance curve to theoretical curves, it is founded that the two curves coincide, which demonstrates our dual-electrodes can used in SECM experiments.In the second part, peroxidase (PO) in a single neutrophil cell and topography are imaged at the same time. First of all, the optimum condition of detection was 1.00×10^-3 mol/L H₂Q, 1.00×10^-3 mol/L H₂O₂ for substrate and PBS for buffer. Digitionin (Dig) in PBS could dissolve cholesterol on the cell membrane and form microhole on it. Such low mass molecules could pass through the membrane while macromolecules such as enzyme were still within the cell (the cell is still live after treated with Dig) .Consequently, H₂Q and H₂O₂ could enter the cell and react under the catalysis of PO to produce BQ and H₂O. When the tip moved above the surface of substrate, which immobilized cells with collagen, it could determine the changes of the concentration of BQ, find cells and detect the activity of intracellular PO by SECM. At the same time, 1.00×10^-3 mol/L K₄Fe(CN)₆ were added in the solution. Immobiled the potential of the other electrode of dual-Au electrodes to the potential that K₄Fe(CN)₆ is oxidated. When the tip moved above the surface of cell, the oxidation current will reduce because of the height of cell. Then the topography is determined.In the third part, alkaline phosphatase (ALP) in a single rat liver cell and activity of respiration are determined at the same time. First of all, the optimum condition of detection was 7.5×10^-4 mol/L p-aminophenylphosphate(PAPP) for substrate and PBS for buffer. After treated with Dig, PAPP could enter the cell and react under the catalysis ofALP to produce p-aminophenol (PAP) . When the tip moved above the surface of substrate, which immobilized cells with collagen, it could determine the changes of the concentration of PAP, find cells and detect the activity of intracellular ALP by SECM. At the same time, the oxygen around the cell will decrease because of the respiration of cell. When the tip move above the cell, the reduction current of oxygen will decrease. So that we can detect the activity of respiration of cell.