An electrochemical immunosensor based on ensemble protein labelling for point-of-care diagnostic applications Mohamed Sharafeldin University of Otago, New Zealand Point-of-care (POC) protein sensors are pivotal for accessible, low-cost, sensitive, and fast disease diagnostics that can support personalized healthcare systems. Electrochemical platforms have served as a launchpad for a multitude of POC sensors, promising accessibility and sensitivity, but usually require multi-step procedures that increase the cost and complicate the automation process. Herein, we describe a novel approach that can reduce the number of steps and reagents required for an electrochemical immunoassay while maintaining similar sensitivity to those sensors employing conventional immunoassay formats. We demonstrate the use of shotgun (ensemble) protein tagging using a redox-active covalent labeling reagent targeting free amine groups of the protein amino acid side chains. This is followed by a selective recruitment of the (labeled) target proteins on antibody-modified electrodes that can elicit a highly specific and sensitive electrochemical signal. This assay was applied to the duplex analysis of C-reactive protein (CRP) and cardiac troponin-I (cTnI) with detection limits at pg/mL levels and a dynamic range spanning over several orders of concentrations. The assay was integrated within a semi-automated microfluidic chip that supports a 15-minute sample-to-answer platform. This modular design can be adapted into an array of immune-sensing applications that can be easily tailored by engineering the antibody layer on the electrode surface. References 1. M. Sharafeldin and J. J. Davis, Analytical Chemistry , 2021, 93 , 184-197. 2. M. Sharafeldin, F. Fleschhut, T. James and J. J. Davis, Analytical Chemistry , 2022, 94 , 2375-2382.
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