Charaterization Of A Plasma Source Used To Accelerate Wound Healing Of The Tadpole Xenopus Laevis*

Abstract

A recent application of plasma jets has involved the healing of wounds in the tadpole species Xenopus laevis 1. The indirect application of the plasma to the amputated tail of the tadpole produced a faster rate of growth, elevated reactive oxygen species in the cellular structures, and an increase in antioxidant enzymes in the regenerate compared to that of the untreated control. The plasma exposure accelerated the dynamics of the wound healing and tail regeneration through its effects on cell proliferation and differentiation, as well as, angiogenesis mediated through reactive oxygen signaling. The discharge source operated with high purity Helium gas at a flow rate of 50sccm that passed through a ¼” quartz tube. A copper electrode was attached to the outer surface of the tube at a point 5.0cm from the end of the tube. Attached to the electrode was an AC power supply operating at 32kHz and 12kV. The system was operated in a regime such that the discharge was restricted to the flow region between the electrode and the exit aperture of the tube. The profiles of the emissions features were measured using a high-resolution spectrometer coupled to an CCD detector. The spectra indicated that molecular nitrogen was present within the tube in both the neutral and ionized states. OH emissions, in the wavelength region between 300–315nm, were observed inside the tube and extending outside of the quartz tube. The emission profile of the Second Positive Systems was used to calculate the vibrational temperature and it was found to be 375±50K. The rotational temperature was determined from a fitting of the Second Positive System transition at 337nm to a Boltzmann distribution and it was found to be 375±50K. The current was measured by monitoring the ground connection from a metal plate that was placed adjacent to the exit aperture of the quartz tube using a current transformer. When the system was powered without a plasma the signal consisted of a sinusoidal wave having an amplitude of less than 0.5mA at a frequency that matched the driving voltage (32kHz). When the plasma was “on” the signal consisted of an additional component superimposed on the sinusoidal wave. The additional component was a short duration (1 μs) positive current pulse (0.75mA) that appeared approximately at the time the high voltage reached its maximum value. The height of this current pulse decreased with distance from the exit aperture of the quartz tube.