Vibrating probe technology and its applications in biological engineering.

摘要

Bioelectric currents and the role they play in developmental physiology is a major research area actively pursued by researchers over the last century. Key findings in this area have always been related with subsequent advancement in technology which enables sensitive recording of these currents with minimal impact on the biological system. Initially dominated by intracellular electrodes for measuring bulk tissue and then single cell recordings, the Vibrating Probe technique was a significant breakthrough for electrophysiology. Pioneered by Jaffe and Nuccittelli around the same time that patch clamp technology appeared on the horizon, this technique for the first time allowed non-invasive measurements of current densities associated with small electric fields with high spatial and temporal resolution. This technique was originally developed to measure current densities associated with total ionic current traversing a certain extracellular location of a biological cell, tissue or organ immersed in a medium. Widely used for measuring developmental currents on plant cells, embryos, injury currents and regeneration currents, it has also found widespread application in the corrosion industry. Here, we report for the first time measurement of enormous electric currents (ionic) traversing into the site of injury of guinea pig spinal cords using the 2-D vibrating probe technology. Time dependent decay of this injury current was measured and the diffusion profile of these ionic currents was also studied. Finally, a biophysical analysis was performed on this data to obtain a mathematical model which predicts the instantaneous surface injury current density. Injury current densities associated with ventral portion of the spinal cord were measured to be higher then those associated with the dorsal portion with the highest being close to 1mA/cm2. Additionally the vibrating probe technique was for the first time also applied to characterize the current density profile associated with a MEMS based microelectroporation device. This thesis thus aims to further our understanding of the role of extracellular injury currents in spinal cord injury and regeneration and reviving the vibrating probe technology as an effective tool for developmental biology and other engineering applications.