Chronic wounds in the community

: a smart device approach to detecting the early onset of infection

Abstract

The prevalence of chronic wounds in the community is constantly rising due to an aging population and, with the current stress and pressure on the healthcare system, their management is an increasing burden on services. Taking a prolonged time to heal, the wound is vulnerable to bacterial exposure. Post exposure, if bacteria multiply, this may lead to infection, and become serious resulting in sepsis, osteomyelitis or amputation. A device that actively monitors the condition of chronic wounds, and that provides an early warning system for infection, could translate into significant economic savings, ultimately preventing unnecessary complications.

This research has focused on pH, moisture, and C-reactive protein (CRP) as potential biomarkers of wound status, exploring the use of laser induced graphene (LIG) substrates. Potentially serving as a foundation for smart wound diagnostics, LIG systems were developed through laser etching of a polyimide substrate, resulting in a carbon based (graphene) material which was electrically conductive. The various LIG designs were studied using a variety of surface characterisation techniques, reaction mechanisms and sensing capabilities elucidated through the use of electrochemical techniques.

Due to its inherent biocompatibility, riboflavin was employed as a pH dependent redox probe which could allow the voltametric measurement of pH. As bacterial infection can shift wound pH, this method was evaluated, and the accuracy of the responses validated using blood samples. The oxidation potential window of riboflavin was found to rest outside the oxidation region of common interferents found in a wound environment and was found to shift with increasing pH to more negative potentials, with a near-Nernstian shift (E/V = 0.047 pH - 0.162; N = 24; R2 = 0.995) with pH. An average difference of +/- 0.03 compared to a commercial pH probe demonstrates the sensor’s accuracy.

The LIG electrodes were further modified with chitosan and carbon nanoparticles, with the intrinsic hydrophilicity of the former resulting in swelling of the film and subsequent changes in resistance. This allowed for moisture measurements, where significant changes in moisture levels could be indicative of infection. The system demonstrated a linear response with a high sensitivity (y = 20.98x + 3391 ; R2 = 0.990) alongside a quick recovery time of 219 s.

Finally, LIG was employed as the base substrate of a molecularly imprinted polymer system for the detection of CRP and hence its possible use as a diagnostic for infection. The MIP electrodes generated a linear response to CRP concentrations (R2 = 0.997 / 0.988), whilst providing a reversible technique that could allow for constant monitoring to provide regular measurements. Sensors also demonstrated increased selectivity to the CRP molecule imprint compared to molecules such as BSA.

Date of Award	Sept 2023
Original language	English
Sponsors	Department for the Economy
Supervisor	Jill Cundell (Supervisor), Chris Gill (Supervisor) & Kirsty Pourshahidi (Supervisor)