Using impedance spectroscopy to monitor the regeneration of newt tails

This paper describes the application of impedance spectroscopy, a standard materials science technique, to biological tissue. Newts can regenerate their limbs; people cannot. In recent years considerable interest has developed regarding what factors control this regeneration with the goal of improving wound healing, or perhaps eventually developing some form of limb regeneration, in mammals. We examine the potential of impedance spectroscopy to provide a relatively simple and inexpensive means to monitor the progress of tail regeneration. Using a Solartron 1260 Impedance Analyzer between 1 Hz and 30 MHz, we measured for nine newts the variation of impedance spectra over time as the tail regenerated. With the corresponding dimensions of the regenerating tail we determined the tissue conductivities. We modeled the tail itself electrically as a series combination of two parallel Constant-Phase Element/Resistance (CPE/R) elements and another resistor that accounts for dispersions above 1 MHz. The conductivities associated with one CPE/R term and the high-frequency term showed a definite increase during the stage when differentiation was beginning in the tail and then leveled off. The conductivity of the other CPE/R term is probably determined by counterion polarization and changes in it may indicate the development of cartilage rod into the spine. We conclude that some impedance changes correlate with stages in the regeneration of a newt tail.