Smart Bandage to Monitor Combat Wounds and Control Bacterial Infections During Military Operations

Bhansali, Shekhar

In the United States Army, nearly 50% of soldiers experience 1 or more injuries a year during deployment and mission operations. The most common injuries during these operations can be classified between saturable wounds, such as lacerations and punctures, and non-saturable wounds, such as blast wounds, gunshot wounds, head injuries, bone fractures, burns, and ulcers. In all cases, the leading post-wound treatment are complications associated with wound infections; with sepsis being the leading cause of death in after wound care. Gram-positive, gram-negative, and fungal infections are the most prevalent types of infections seen in the U.S. Army, with Staphylococcus aureus (s. aureus) being the most common infection recorded in about 20% of soldiers. Present techniques are limited to using pressure pads and antibacterial gels for preventing infections. These approaches cannot be integrated into a wearable construct and do not offer a reliable method of management. Therefore, monitoring and treating infection in combat wounds is a major healthcare challenge in wound care management for army application.

Our work focuses on developing a wearable smart bandage that can detect a change in pH and lactate using an electrochemical sensing approach that responds as a function of bacterial infection and can monitor in real-time using data generated by sensors. Further, the pH sensing causes a triggered release of drug molecules that control bacterial infection in the wound bed. The electrochemical pH sensors were fabricated by printing commercial flexible inks onto a stretchable thermoplastic polyurethane (TPU, TE-11C DuPontTM) film, and subsequently heat laminating over a cotton gauze (thickness: 100 μm). A conventional three-electrode cell assembly consisting of SPCE, Ag/AgCl as a reference electrode, and a Pt wire as a counter electrode was used for the experiments. CV was performed to assess the performance of the electrodeposited polyaniline. The measurements were performed at a scan rate of 0.02 V s-1 in a potential window of 1 V and -0.2 V. Sensor stability was characterized under room temperature and physiological conditions (RT) over 3 days. In case of the triggered drug release, we synthesized chitosan-pH responsive polymer using an ionic gelation process and drug ampicillin and kanamycin were encapsulated with a 64% efficiency. The polymer released drug above pH 6.5 which correlated to 10⁵ bacterial CFU/ml, thus was incorporated in the bandage matrix and served as a controlled release when infection occurs. It was observed that pH tends to rise as infection progress therefore ideal for drug release in an alkaline environment.

Finally, the sensor was able to detect bacterial cells ranging from 10²-10⁵ cells and the drug release showed an 82% reduction in cell number. The work carried out highlights an integrated sensor to sense bacterial infections and simultaneously trigger drug release. In light of current findings, this study allowed us to understand the dynamic interaction occurring between the sensor surface and wound bed and the sensor data showed a direct correlation to bacterial infection. The sensor can be integrated into a multiplex wearable device detecting different biomarkers to simultaneously monitor and manage infection in combat as well as chronic wounds.