Development of immunosensors for direct detection of three wound infection biomarkers at point of care using electrochemical impedance spectroscopy

► We develop a method for label-free electrochemical impedance immunosensing. ► We apply this method to the detection of three infection biomarkers. ► We show this can detect directly from biological matrices. ► We demonstrate the required sensitivity for rapid and clinically relevant wound infection detection. A method for label-free, electrochemical impedance immunosensing for the detection and quantification of three infection biomarkers in both buffer and directly in the defined model matrix of mock wound fluid is demonstrated. Triggering Receptor-1 Expressed on Myeloid cells (TREM-1) and Matrix MetalloPeptidase 9 (MMP-9) are detected via direct assay and N-3-oxo-dodecanoyl-l-HomoSerineLactone (HSL), relevant in bacterial quorum sensing, is detected using a competition assay. Detection is performed with gold screen-printed electrodes modified with a specific thiolated antibody. Detection is achieved in less than 1h straight from mock wound fluid without any extensive sample preparation steps. The limits of detection of 3.3pM for TREM-1, 1.1nM for MMP-9 and 1.4nM for HSL are either near or below the threshold required to indicate infection. A relatively large dynamic range for sensor response is also found, consistent with interaction between neighbouring antibody–antigen complexes in the close-packed surface layer. Together, these three novel electrochemical immunosensors demonstrate viable multi-parameter sensing with the required sensitivity for rapid wound infection detection directly from a clinically relevant specimen.