Chronic Wounds Point-of-care system for monitoring moisture, temperature, pH, Interleukin-6 and Uric Acid levels

Chronic wounds are those that take longer than three months to heal or do not show improvements after prompt treatment, being more likely to become infected or colonised by bacteria. Currently, the most prevalent methods for managing chronic wounds are visual assessment and diagnostic dressing, which have significant financial impacts on the healthcare sector.

Chronic wounds impact 5.7 million people in the US and cost $20 billion annually. (Brown , Ashley, & Koh, 2018) (Tran, et al., 2022) A few of the pressure, chemical, and optical sensors that have been explored for non-invasive wound monitoring are currently on the market. However, a microsystem that can detect moisture, temperature, pH, and chemical biomarkers is required to have a more complete wound monitoring system. (Tran, et al., 2022)

Continuous temperature increases of at least 1.11 degree C at the wound may be caused by infections or changes in metabolism, hence it is essential to frequently monitor the tissue temperature and moisture level to decide when to change the bandage or remove necrotic tissue. (Tran, et al., 2022) (Brown , Ashley, & Koh, 2018) Chronic wounds have a pH between 7.18 and 8.90, which results in a mildly basic environment that promotes bacterial colonisation. pH measurements alone are insufficient for infection monitoring, but when combined with additional biomarkers such uric acid (UA) and interleukin-6 (IL-6), they may be useful for detecting infections early on and the extent of the inflammatory phase. (Brown , Ashley, & Koh, 2018). (Pusta , Tertis, Cristea, & Mirel, 2022).

The purpose of this project is to develop a flexible wearable system that includes inexpensive wireless temperature, moisture, and pH sensors as well as electrochemical biosensors for measuring, IL-6, and UA levels. This point-of-care (POC) system would act as a multifunctional in situ device that can diagnose wound parameters and regulate the infection at the wound site offering the potential to enhance available treatment options.

The structure of the device would include an outer flexible textile substrate with integrated electronics, an (disposable) active layer on top with printed temperature, moisture, and electrochemical biosensors, and then a layer of absorbent material that would encounter the wound. Owing to its high electrical and thermal conductivity, high carrier mobility, functionality, and biocompatibility, liquid-phase exfoliated graphene will be addressed as the primary active material for temperature and electrochemical biosensors. (Davies, Tzalenchuk, Wiper, & Walton, 2016)

For the temperature sensors the thermal conductivity of graphene will be exploited by printing graphene or graphene/temperature-sensitive polymers inks into sensor arrays (thermistors). (Ismail, Idris, & Abdullah, 2022) (Yan, Wang, & Lee, 2015) (Servati, Zou, Wang, Ko, & Servati, 2017). An optimal encapsulation method, biocompatible substrate material (i.e., polylactic acid (PLAA), cellulose, and chitosan) and correction method for signal susceptibility to motion and strain will be investigated.

For the moisture sensor, electrodes made of conductive materials (i.e., graphene, Ag, and AgCl) will be taken into consideration. (McColl, MacDougal, Watret, and Connolly, 2009) When a small current is delivered to these electrodes by a portable metre, the electrical impedance across the sensor electrodes will allow the moisture level to be detected. As an alternative, ion-conductive polymeric electrodes (i.e., PEDOT: PSS, PPy, PANI) will be printed that, when in contact with the ion-rich exudate, will modify their ionic electronic conduction mechanism, extrapolating into impedance changes. (Tessarolo, et al., 2021)

To detect chemical biomarkers and monitor pH levels, inkjet-printed EnFET (enzyme field-effect transistor devices) and ISFET (ion-selective field-effect transistor) will be investigated respectively.