Abstract
Rapid advances in clinical technologies, detection sensitivity and analytical throughput have delivered a significant expansion in our knowledge of prognostic and diagnostic biomarkers in many common infectious diseases, such as Tuberculosis (TB). During the last decade, a significant number of approaches to TB diagnosis have been attempted at Point-of-Care (PoC), exploiting a large variation of techniques and materials. In this work, we describe an electronics-based Enzyme-Linked ImmunoSorbent Assay (eELISA), using a Lab-on-a-Printed Circuit Board (LoPCB) approach, for TB diagnosis based on cytokine detection. The test relies upon an electrochemical (amperometric) assay, comprising a high-precision bioinstrumentation board and amperometric sensors, produced exclusively using standard PCB manufacturing processes. Electrochemical detection uses standard Au and Ag electrodes together with a bespoke, low-power, multichannel, portable data-acquisition system. We demonstrate high-performance assay chemistry performed at microfluidic volumes on Au pads directly at the PCB surface with improved limit of detection (~10 pg/mL) over standard colorimetric ELISA methods. The assay has also been implemented in plasma, showing the utility of the system for medical applications. This work is a significant step towards the development of a low-cost, portable, high-precision diagnostic and monitoring technology, which once combined with appropriate PCB-based microfluidic networks will provide complete LoPCB platforms.
Highlights
There are many reasons why PoC diagnostics have yet to become mainstream among developed economies
With the intention of producing a complete hand-held biosensor for the detection of IFNγ, the detection range was focused on the clinically relevant range associated with Mycobacterium tuberculosis infection
An existing colorimetric diagnostic assay system was adapted to operate with reduced volume, with assay components localised on Au sensor surfaces
Summary
There are many reasons why PoC diagnostics have yet to become mainstream among developed economies. Newbury Electronics, manufacture the prototype PCBs to include fully embedded microfluidic architecture and Au/Ag amperometric electrodes at the PCB surface. We show entirely novel PCB designs, improving sensitivity over commercial colorimetric and published amperometric systems, combined with detailed analyses of pre-calibration performance with reference to clinical diagnostics. In the clinical laboratory interferon gamma release assays (IGRA’s) are used routinely in at risk populations to diagnose latent TB infection (LTBI)[17] These commercial assays are based on the principle that T-cells in TB patients respond to re-stimulation with TB specific antigens (CFP-10, ESAT-6 and TB7.7) by producing IFNγ. Published research work from our group detailed early results using PCB-based assay technology for the detection of IFNγ using a commercial potetiostat and provides comparative results from other colorimetric and amperometric endeavours[20]. We demonstrate assay functionality in a blood plasma matrix to reflect the final intended application
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