Wearable Textile Sensors for Uric Acid Detection in Wound Exudate

Hard-to-heal wounds (i.e. severe and/or chronic) are typically associated with particular pathologies or afflictions such as diabetes, immunodeficiencies, compression traumas in bedridden people, skin grafts or third-degree burns. In this situation it is critical to constantly monitor the healing stages and the overall wound condition to allow for better targeted therapies and a faster patient recovery. At the moment, this operation is performed by removing the bandages and visually inspecting the wound, putting the patient at risk of infection and disturbance of the healing stages. Recently, new devices have been developed by our research group to address these issues by monitoring pH and moisture in wound fluid, as they are two important biomarkers related to the wound health status. In this contribution we present a novel textile chemical sensor exploiting an organic electrochemical transistor (OECT) configuration based on poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS) for uric acid (UA) selective monitoring in wound exudate. The combination of special medical-grade textile materials provides a passive sampling system which enables the continuous, real-time and non-invasive analysis of wound fluid to monitor the health status of wounds, as UA concentration is a relevant biomarker associated with infections or necrotization processes in human tissues. The sensors are realized by screen-printing a conductive ink based on PEDOT:PSS on medical gauzes, while the appropriate electrical connections are made by sewing conductive textile threads. UA determinations were conducted by means of potentiostatic electrochemical techniques both in phosphate buffers solutions (PBS) and synthetic wound exudate (SWE) while operating in flow conditions to simulate wound fluid delivery using an HPLC pump at a flow rate of 0.05 mL/min. The sensors here developed proved capable of responding reversibly to variations of UA concentration in the biological range of interest for wound exudate (220 - 750 µM), displaying a normalized current response (NCR) equal to a 47% signal variation per 10-fold increase in UA concentration (R2 = 0.98). The values obtained in PBS and SWE were found to be statistically comparable, as confirmed by a t-test (P = 0.95).