Development of a high-sensitivity electrochemical immunoassay using a fully 3D-printed electrocatalytic microelectrode probe platform

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Docherty, Niamh and Miller, Chloe and Dobrea, Alexandra and MacDonald, Daniel and Gordon, Alisdair and Pang, Susan and Fu, Ying and Jimenez, Melanie and Corrigan, Damion and Patel, Bhavik (2026) Development of a high-sensitivity electrochemical immunoassay using a fully 3D-printed electrocatalytic microelectrode probe platform. Analytical Chemistry. ISSN 0003-2700 (In Press) (https://doi.org/10.1021/acs.analchem.5c08037)

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Abstract

Electrochemical biosensors are a promising route to point-of-care diagnostics; however, translation is hindered by the need for electrode surface functionalisation, which introduces variability, increases cost and production complexity, and limits scalability and stability. Additive manufacturing using conductive filaments for rapid fabrication of three-dimensional (3D) electrodes that overcome these limitations. This study evaluates composite filaments comprising polylactic acid (PLA) and multi-walled carbon nanotubes (MWCNTs) used for fused filament fabrication (FFF) of electrochemical electrodes for indirect detection via TMB⁺ measurement. Both filament composition and electrode size were directly compared to determine the most suitable electrode architecture for sensitive measurements in complex samples. As a key novelty, electrode diameter was reduced from 1 mm to the microscale to investigate the influence of size on electron transfer efficiency. To improve measurement consistency and throughput, a 3D-printed assay accessory (“The Consistent Dipper”) was developed to guide electrode immersion and reduce movement during amperometric measurements. PLA/MWCNT microelectrodes exhibited increased current density and reduced background noise compared to carbon black filament electrodes. The micro-MWCNT electrodes were subsequently applied to a cardiac troponin I (cTnI) electrochemical immunoassay. In undiluted human serum, a cTnI c detection limit of 7.4 pg mL⁻¹ was achieved, representing an approximately 19-fold improvement compared to PLA/MWCNT macroelectrodes (140 pg mL⁻¹). Following optimisation to reduce incubation times, a clinically relevant detection limit of 85 pg mL⁻¹ was obtained within a total assay time of 1 h. By combining enhanced electrochemical performance with low-cost, flexible FFF-printed microelectrodes, this platform provides a scalable route to rapid immunodiagnostics. This study represents the first application of microscale 3D-printed PLA/MWCNT electrodes for clinical biomarker detection using a readily manufacturable sensor system.

ORCID iDs

Docherty, Niamh, Miller, Chloe, Dobrea, Alexandra, MacDonald, Daniel ORCID logoORCID: https://orcid.org/0000-0002-9250-434X, Gordon, Alisdair ORCID logoORCID: https://orcid.org/0009-0008-8411-8052, Pang, Susan, Fu, Ying ORCID logoORCID: https://orcid.org/0000-0002-8196-6493, Jimenez, Melanie ORCID logoORCID: https://orcid.org/0000-0002-4631-0608, Corrigan, Damion ORCID logoORCID: https://orcid.org/0000-0002-4647-7483 and Patel, Bhavik;
CORE (COnnecting REpositories)