Success and side effects of different treatment options in the low current attack of bacterial biofilms on titanium implants

[Display omitted] •Combinations of anodic and cathodic treatment in chloride containing electrolytes.•Optimized electrochemical attack on E. coli biofilms for short treatments.•High killing efficacies (greater than 98%) for low current densities of 1 and 2 mA/cm2.•Combined anodic and cathodic treatment not superior to pure cathodic treatment.•First signs of pitting corrosion for anodic treatment even with low current densities.•Synergistic effects of cathodic treatment with chlorhexidine in attacking biofilms. The long-term success of peri-implantitis treatments is generally insufficient. Attacking the bacteria on the titanium implant surface using electrochemical polarization could be an alternative approach. In this study an E. coli biofilm in phosphate buffered saline was treated with low current densities (0.25 to 2 mA/cm2) using anodic, cathodic, or combined polarization regimes, either alone or with the antiseptic chlorhexidine. The antibacterial effect was assessed using LIVE/DEAD® staining and through quantification of viable bacteria, sample surfaces were characterized pre- and post-treatment with electrochemical impedance spectroscopy. All polarization treatments had an antibacterial effect that increased with current density, with at least 1 mA/cm2 necessary to reduce colony forming units by four orders of magnitude. Cathodic treatment was slightly superior to anodic treatment, and there was no difference between alternating polarization and single-type polarization. Neither treatment resulted in a significant detachment of bacteria, but combination with chlorhexidine improved the antibacterial effect synergistically. The use of chloride containing electrolytes is not recommended in this context. The low current densities used here were not sufficient to generate adequate bactericidal chlorine reactive species, but first signs of pitting corrosion were already detected for anodic polarization at 1 mA/cm2.