Table 3.

A summary of the in vitro studies that evaluated effects of electrical stimulation on bacteria that were cultured directly on the stimulating electrode

Reference	Stimulation type	Electrical configuration	Electrode materials*	Stimulation parameters	Bacteria	Results
van der Borden et al. [106]	Current-controlled	Two electrodes connected to a constant current source and placed in a parallel plate flow chamber with potassium phosphate buffer	Stainless steel (WE) Indium-tin-oxide (CE)	15 or 100 µA applied for 2.5 h	Staphylococcus epidermidis initially adhered to stainless steel	Application of 100 µA for 150 min caused an average detachment of 54% of initially adherent bacteria from stainless steel cathodes
van der Borden et al. [94]	Current-controlled	Two electrodes connected to a constant current source and placed in a parallel plate flow chamber with phosphate buffered saline	Stainless steel (WE) Indium-tin-oxide (CE)	15, 60, or 100 µA block currents (5–50% duty cycle at 0.1–2 Hz) applied for 2.5 h	Staphylococcus epidermidis initially adhered to stainless steel	Application of electric block currents of 100 µA (25–50% duty cycle, 0.1–2 Hz) caused an average detachment of 76% of initially adherent bacteria from stainless steel cathodes
van der Borden et al. [95]	Current-controlled	Two electrodes connected to a constant current source and placed in a parallel plate flow chamber with phosphate buffered saline	Stainless steel (WE) Indium-tin-oxide (CE)	60 or 100 µA either DC or block current (50% duty cycle at 1 Hz) for 360 min	Staphylococcus epidermidis biofilms preformed on electrodes	Application of 100 µA for 360 min caused an average detachment of 78% of biofilm associated bacteria, while 100 µA electric block current (50% duty cycle, 1 Hz) yielded only 31% detachment
Rabinovitch et al. [87]	Voltage-controlled	Two electrodes connected to 6 V battery and placed in a beaker or dish filled with saline	Stainless steel	6 V applied from 10 s to 5 min	Staphylococcus epidermidis biofilms pre-formed on electrodes	Electrodes connected to the negative terminal of the battery for 30 s had physically disrupted biofilms and reduced the amount of surface-associated viable bacteria by four orders of magnitude
Dargahi et al. [71]	Voltage-controlled	Three electrodes connected to a potentiostat and placed in unspecified chamber filled with phosphate buffered saline	Stainless steel (WE) Graphite (CE) Ag/AgCl (RE)	− 0.5 V to − 3.0 V for up to 60 s	Pseudomonas aeruginosa biofilms pre-formed on stainless steel electrodes	Cathodic polarization greater than − 1.5 V versus Ag/AgCl for 60 s or less removed the biofilms
Costerton et al. [70]	Current-controlled	Three electrodes connected to a direct current generator and placed into a flow cell with culture media	Stainless steel	polarity of adjacent electrodes alternate every 64 s with an average current density of 1.7 mA/cm2	Pseudomonas aeruginosa biofilms pre-formed on stainless steel electrodes	Application of this electrical stimulation pattern for 48 h in the presence of five times the minimal inhibitory concentration of tobramycin produced an almost complete kill of P. aeruginosa biofilms preformed on the stainless steel
Mohn et al. [80]	Current-controlled	Two electrodes connected to an unspecified electric circuit. Electrodes separated by electrically conductive ballistics gel	Titanium dental implants	2, 5, 7.5, 10 mA for 15 min	Escherichia coli biofilms pre-formed on electrodes	7.5 mA and 10 mA completely killed all bacteria at the anode and reduced viable bacteria by two orders of magnitude at the cathode
Schneider et al. [89]	Voltage-controlled	Two electrodes connected to a potentiostat. Electrodes separated in an electrolysis chamber	Titanium dental implants (cathode) and platinum (anode)	7.0 V and 300 mA for 30 s	Mixed species wildtype biofilms pre-formed on titanium electrode	Bacterial biofilm was completely removed from a titanium dental implant (cathode) upon application of optimized electrolysis stimulation of 30 s at 7.0 V and 300 mA
Ehrensberger et al. [65]	Voltage-controlled	Three electrodes connected to a potentiostat. Electrodes were immersed in saline and separated by electrically conductive agar	Titanium (WE) Graphite (CE) Ag/AgCl (RE)	− 1.8 V for 1 h	Methicillin-resistant Staphylococcus aureus biofilms pre-formed on titanium electrode	Application of − 1.8 V for 1 h significantly reduced the CFU enumerated from the pre-formed biofilm on the titanium by 97% and from the planktonic bacteria in the surrounding solution by 92%
Canty et al. [100]	Voltage-controlled	Three electrodes connected to a potentiostat. Electrodes were immersed in culture media and separated by electrically conductive agar	Titanium (WE) Graphite (CE) Ag/AgCl (RE)	− 1.5 V or − 1.8 V for 2, 4, 8 h	Methicillin-resistant Staphylococcus aureus or Acinetobacter baumannii planktonic	No detectable titanium coupon-associated or planktonic CFU for either MRSA or A. baumannii were enumerated following − 1.8 V for 8 h. Applying − 1.8 V for 4 h reduced titanium coupon-associated MRSA and A. baumannii CFU by 99.9% and reduced planktonic CFU below detectable levels for both strains
Canty et al. [69]	Voltage-controlled	Three electrodes connected to a potentiostat. Electrodes were immersed in culture media and separated by electrically conductive agar	Titanium (WE) Graphite (CE) Ag/AgCl (RE)	− 1.0 V, − 1.5 V, or − 1.8 V for 24 h	Methicillin-resistant Staphylococcus aureus or Pseudomonas aeruginosa planktonic and biofilms pre-formed on titanium electrode	Applying − 1.8 V for 24 h eradicates MRSA and P. aeruginosa biofilms pre-formed on titanium surfaces. Synergistic reductions in MRSA and P. aeruginosa biofilms when CVCES at − 1.5 V was delivered to the titanium for 24 h in combination with clinically relevant antibiotics. 24 h of CVCES at − 1.5 V in combination with antibiotic prophylaxis was able to prevent MRSA and P. aeruginosa attachment on titanium coupons

*Note that WE is the working electrode, CE is the counter electrode, and RE is the reference electrode