A primary current distribution model of a novel micro-electroporation channel configuration

Traditional macro and micro-electroporation devices utilize facing electrodes, which generate electric fields inversely proportional to their separation distance. Although the separation distances in micro-electroporation devices are significantly smaller than those in macro-electroporation devices, they are limited by cell size. Because of this, significant potential differences are required to induce electroporation. These potential differences are often large enough to cause water electrolysis, resulting in electrode depletion and bubble formation, both of which adversely affect the electroporation process. Here, we present a theoretical study of a novel micro-electroporation channel composed of an electrolyte flowing over a series of adjacent electrodes separated by infinitesimally small insulators. Application of a small, non-electrolysis inducing potential difference between the adjacent electrodes results in radially-varying electric fields that emanate from these insulators, causing cells flowing through the channel to experience a pulsed electric field. This eliminates the need for a pulse generator, making a minimal power source (such as a battery) the only electrical equipment that is needed. A non-dimensional primary current distribution model of the novel micro-electroporation channel shows that decreasing the channel height results in an exponential increase in the electric field magnitude, and that cells experience exponentially greater electric field magnitudes the closer they are to the channel walls. Finally, dimensional primary current distribution models of two potential applications, water sterilization and cell transfection, demonstrate the practical feasibility of the novel micro-electroporation channel

1H magnetic resonance imaging of freezing and thawing in freeze-tolerant frogs

Proton magnetic resonance imaging (MRI) of the processes of freezing and thawing in the wood frog Rana sylvatica provided noninvasive and real-time analysis of the mode of ice propagation through the body of a freeze-tolerant vertebrate. MRI revealed a directional movement of ice from the exterior inward that required several hours to reach completion. Freezing in core organs such as liver, which produces and exports cryoprotectant, and heart, which circulates it, was delayed and occurred well after the organs were surrounded by extraorgan ice. Natural thawing was a very different process; thawing began uniformly throughout the body, but core organs melted more rapidly than peripheral ones, an adaptation that may be key to the early restoration of heartbeat and breathing. The images presented demonstrate the sensitivity and power of MRI and its potential to become a critical monitoring technology in the development of cryopreservation techniques for mammalian organ explants