The Effects of Electrochemical Potential on the Growth of Escherichia coli and Bacillus megaterium Colonies on Conductive Agar Plates

A recent study by Vomaris et al., demonstrated that a wireless electroceutical device (WED) consisting of a series of silver and zinc electrodes could be used as a “smart” bandage, which inhibits microbial biofilm formation on burn victims. The antibacterial and electrochemical properties of silver and zinc drive the WED technology. This antibacterial effect is complicated by the presence of established antimicrobial metals like Ag and Zn in the device. We performed experiments on biocompatible solid media to determine if this antibacterial effect is based on electrochemical potential and not the metals present in the device. We created carbon-based drop cast electrodes containing either Fe(s)/C, Zn(s)/C versus Ag(s)/C or Pt/Carbon electrodes to inhibit the growth of Escherichia coli or Bacillus megaterium in regions between the electrodes. We created single and dual electrode systems on nutrient rich agar plates with defined electrical conductivities. We confirmed that neither Fe(s)/C nor Pt/C electrodes inhibit the growth of either bacterium. However, the Zn(s)/C electrode inhibits the growth of both E. coli and B. megaterium up to 1 cm from the edge of the electrode. The dual electrode systems containing non-toxic metals have thus far not inhibited the growth of either bacterium when both anodes and cathodes were drop cast on the agar surface. However the devices did generate open circuit potentials starting at 450 mV to approximately 150 mV over 8 days. We present how blending vulcan carbon (XC-72) into the agar can decrease the resistance of the agar by 1000x without impacting the growth of either bacterium. Our results indicate that printable carbon based electrodes can potentially sensitize bacteria to antibacterials, but to date the electrochemical effect is not strong enough to thwart the growth of E. coli or B. megaterium.https://ecommons.udayton.edu/stander_posters/3017/thumbnail.jp