RESUMEN
The shell of the Eastern oyster (Crassostrea virginica) is composed of multiple incongruent mineralized layers. This bioceramic composite material was investigated to determine the effects of shell thickness, orientation and layer composition on its electrochemical behavior using electrochemical impedance spectroscopy, potentiodynamic polarization and scanning electron microscopy-energy dispersive spectroscopy. SEM-EDS analysis of the oyster shell revealed that the multilayered biocomposite material is composed of calcium carbonate (CaCO(3)). EIS measurements in 3.5wt.% NaCl indicated that the impedance of the whole oyster shell in the low frequency region exhibited high impedance values which exhibited a decreasing trend with increasing immersion time. In terms of overall shell thickness, limiting currents measured by potentiodynamic techniques through the shell were observed to increase when the outer layers of the shell were sequentially removed by grinding, thus decreasing the shell thickness. These limiting current values remained relatively constant when the inner layers of the shell were removed. The impedance values of the oyster shell material as measured by EIS were shown to decrease with decreasing shell thickness. These findings suggest that the prismatic (outermost) shell layer in combination with the soluble organic matrix between all shell layers may influence the ionic conductivity through the oyster shell.
Asunto(s)
Óxido de Aluminio/análisis , Óxido de Aluminio/química , Carbonato de Calcio/química , Crassostrea/metabolismo , Animales , Espectroscopía Dieléctrica/métodos , Impedancia Eléctrica , Microscopía Electrónica de Rastreo/métodosRESUMEN
Response of a conductive micromechanical cantilever placed in close proximity to a surface undergoing electrical excitation near the resonance frequency of the cantilever is influenced by the presence of microscopic dielectrics in the gap between the cantilever and the sample surface. The variations of the resonance response of unmodified cantilevers at gap distances below a few hundred nanometers are used to discern biomolecular differences of oligomeric nucleic acids in an array format without the use of extrinsic labels. The resonance response variation paves the way for the development of high throughput detection of biomolecular reactions, such as DNA hybridization reactions or antibody-antigen interactions without the use of external labels, in which the need is only to see the presence or absence of interaction. This dynamic method is simple, does not require immobilizing individual elements on a cantilever array, and is compatible with current generation DNA chips in which DNA spots are deposited in micro- and nanoarray format.