Electrochemical corrosion of STS304 acupuncture needles by electrical stimulation.

We present the first investigation of electrical corrosion in acupuncture needles after electrical stimulation. Using scanning electron microscopy, we observed the occurrence of electrochemical corrosion on the surface of stainless steel 304 acupuncture needles after electrical stimulation in the tibial muscles of rats. Biphasic pulse electrical stimuli with 10-Hz frequency, 1-mA intensity and 1-ms pulse width were applied to the needles. The terminal deoxynucleotidyl transferase-mediated dUTP-biotin nick end labeling (TUNEL) method labels fragmented DNA. Positive staining using this test indicates apoptotic cells in electrically stimulated tissues. The risk of electrical corrosion was found to be less in bipolar, short-duration, low-current or voltage and short-period stimulation than in monopolar, long-duration, high-current or voltage and long-period stimulation. Evaluation with a scanning electron microscope revealed that electrical stimulation can increase the electrical corrosion of stainless steel 304 acupuncture needles. In biocompatibility studies of stainless steel 304 acupuncture needles for electrical stimulation, TUNEL-positive cells were detected in the tibial muscle within 5 days after electrical stimulation. The results of this study demonstrate that the corrosion products of stainless steel 304 acupuncture needles might affect the post-electrical stimulation tissue response.