Reducing bacterial adhesion to titanium surfaces using low intensity alternating electrical pulses

Abstract

Background: Orthopedic implant-related infection remains one of the most serious complications after orthopedic surgery. In recent years, there has been an increased scientific interest to improve prevention and treatment strategies. However, many of these strategies have focused on chemical measures.

Aim: To analyze the effect of alternating current electrical fields on bacterial adherence to titanium surfaces.

Methods: Staphylococcus aureus (S. aureus) and Escherichia coli (E. coli) were exposed to 6.5 V electrical currents at different frequencies: 0.5 Hz, 0.1 Hz, and 0.05 Hz. After exposure, a bacterial count was then performed and compared to the control model. Other variables registered included the presence of electrocoagulation of the medium, electrode oxidation and/or corrosion, and changes in pH of the medium.

Results: The most effective electrical model for reducing S. aureus adhesion was 6.5 V alternating current at 0.05 Hz achieving a 90% adhesion reduction rate. For E. coli, the 0.05 Hz frequency model also showed the most effective results with a 53% adhesion reduction rate, although these were significantly lower than S. aureus. Notable adhesion reduction rates were observed for S. aureus and E.coli in the studied conditions. However, the presence of electrode oxidation makes us presume these conditions are not optimal for in vivo use.

Conclusion: Although our findings suggest electrical currents may be useful in preventing bacterial adhesion to metal surfaces, further research using other electrical conditions must be examined to consider their use for in vivo trials.

Keywords: Bacterial adhesion; Electrical fields; Metal surfaces; Orthopedic infection; Titanium.

Figure 1

Design of the 12-well culture plate. A: The connection to the generator, the amplifier, and both electrodes in one of the wells of the plate. The lower electrode acted as a cathode, and the upper electrode acted as an anode; B: Photograph of the function generator with four separate connections to allow four different trials to be performed simultaneously. There are three rows of wells on the culture plate allowing tests to be triplicated.

Figure 2

Electrical field application without bacteria. A: Initial setup of the titanium disks; B: Microscope used to visualize titanium oxidation and bubble formation.

Figure 3

Microbubble formation test and results. A: Microbubble formation at the cathode using a 7 V current; B: Bubble rate formation on the X-axis compared to voltage. Exponential formation of bubbles after 5V.

Figure 4

Results for colony-forming units. A: Results for colony-forming units of Staphylococcus aureus for the studied conditions; B: Results for colony-forming units of Escherichia coli for the studied conditions. S. aureus: Staphylococcus aureus; E. coli: Escherichia coli.

Figure 5

Bacteria inside the lumps formed by electrocoagulation of the medium.

Figure 6

Anodizing of the titanium surfaces.