A point-of-care, label-free OECT sensor for uric acid detection: Validation in human saliva

This study presents the development of an organic electrochemical transistor (OECT) sensor for the detection of uric acid (UA) in human saliva, employing a potentiodynamic measurement technique. Unlike many existing (bio)sensors, this device is entirely based on the organic semiconductor poly(3,4-ethylenedioxythiophene):polystyrene sulfonate (PEDOT:PSS), which simplifies manufacturing and maintenance and reduces production costs. First of all, a systematic comparison between the potentiostatic and potentiodynamic sensing performance in buffer solution is presented, which proves the superior accuracy (14 %), repeatability (5 %), and reproducibility (8 %) of the potentiodynamic approach. In particular, a sensitivity of 59 µS dec⁻¹ is obtained in the concentration range 10 – 350 µM UA, with a detection limit of 1 µM. Selectivity studies and subsequent validation of the potentiodynamic OECT sensor in human saliva with an independent method specific for salivary UA quantification is then presented, after which we show the application of our sensor to salivary UA monitoring during food intake, as well as the attempt to analyze swine saliva. Furthermore, as the sensor's design supports integration with point-of-care platforms, we demonstrate its functionality with portable electronics and smartphone connectivity. This approach enables rapid, real-time monitoring, offering a practical and cost-effective solution for non-invasive UA detection in clinical settings.