Electrical Stimulation of Titanium for the Prevention and/or Eradication of A. baumannii and S. aureus Biofilm Infections on Osseointegrated Prostheses

PUBLIC ABSTRACT

Many of our troops that are injured serving in Iraq and Afghanistan sustain wounds to their extremities. In severe cases the wounded limb may be amputated and subsequently replaced with a prosthetic limb. The socket-type prosthetics that are currently used have certain limitations that can impair the quality of life for the injured soldier. A new type of prosthetic limb is currently being developed that improves upon the socket-type prosthetic limb and offers several advantages. This new prosthesis is made of titanium and is directly anchored (osseointegrated) to the bone present in the residual limb allowing for direct load transfer to the skeleton and better control of prosthetic movement. In addition, patients with these new osseointegrated limbs report regaining some sensory and tactile function of the limb. However, despite these advantages, the widespread utilization of these prostheses has been limited due to concerns of deep infection originating at the site where the titanium protrudes through the skin. The current project is focused on developing a new way of preventing infections from developing or to successfully treat infections that have already been established on titanium osseointegrated prostheses.

Specifically, the idea behind this project is to essentially utilize the titanium implant as an electrode whose voltage can be controlled to deliver electrical stimulation that is optimized to prevent and/or eradicate implant associated infections. Most implant infections are hard to cure because highly resistant biofilms form on the implants that encase the bacteria in a protective coating. The formation of these biofilms is thought to involve specific electrochemical interactions between the bacteria and the implant. Since the electrochemical properties of titanium are voltage-dependant, we hypothesize that by controlling the voltage of titanium implants we can manipulate the electrochemical interactions between the bacteria and the electrified titanium interface such that biofilm formation will be prevented and/or eradicated.

The project will assess the ability of titanium electrical stimulation, either alone or in combination with antimicrobial therapy, to inhibit two prominent pathogens (methicillin-resistant Staphylococcus aureus, and Acinetobacter baumannii) that are of specific relevance to military trauma care. Studies will initially be conducted in standard biofilm flow chambers that are modified to incorporate electrically polarized titanium samples. Additional studies will be performed where electrically polarized titanium samples will be implanted into a rat soft-tissue infection model. The outcomes of these studies will establish a new titanium electrical stimulation protocol for the prevention and/or eradication of biofilm infections on titanium orthopedic implants. The establishment of definitive infection control for titanium implants would enable the widespread utilization of the new osseointegrated prosthetics, which hold great promise for improving the quality of life for our injured military personnel. Furthermore, these studies may establish a new paradigm for the treatment of infections associated with other orthopedic hardware and devices and may ultimately begin to address the growing problem of antibiotic-resistant bacteria.