Development of Conductive Ink-Based Printed Polymer Electrodes for Flexible Biosensor Applications in Point-of-Care Diagnostics Across Nigerian Rural Health Settings

Point-of-care diagnostic biosensors offer critical potential for bridging healthcare access gaps in rural communities across Nigeria's six geopolitical zones, where laboratory infrastructure is limited. This research develops printed polymer electrodes based on conductive polymer inks incorporating polyaniline, polypyrrole, and PEDOT:PSS on flexible polyethylene terephthalate and paper substrates, targeting electrochemical biosensor applications for malaria, typhoid, and glucose detection relevant to Nigerian rural health contexts. The research investigates the synthesis and rheological optimisation of conductive polymer inks for screen and inkjet printing processes, establishing structure-conductivity relationships for printed electrode films. Electrode characterisation includes sheet resistance, electrochemical active area, cyclic voltammetry response, and sensitivity to target biomarkers. Bioreceptor immobilisation strategies using aptamers, antibodies, and enzyme layers were systematically evaluated for stability under tropical ambient storage conditions of 35 degrees Celsius and 75 percent relative humidity representative of South West and South South Nigerian environments. A miniaturised electrochemical readout system compatible with smartphone integration was developed and validated for field diagnostic use. Analytical performance of the printed biosensor platform was characterised through limits of detection, dynamic range, selectivity, and cross-reactivity against interfering species. Clinical validation was conducted using venous blood samples from volunteer participants at a primary healthcare facility in Oyo State, South West Nigeria. Results demonstrate that polyaniline-based electrodes on polyethylene terephthalate substrates achieved sheet resistance of 28 ohm per square with electrochemical active area comparable to commercial screen-printed carbon electrodes. Malaria antigen detection limits reached 0.18 ng/mL, meeting World Health Organisation rapid diagnostic test sensitivity requirements. Storage stability testing confirmed less than 12 percent sensitivity loss after 90-day ambient storage, a critical requirement for supply chain reliability in rural Nigerian settings. The research establishes a complete printed polymer electrode technology platform for low-cost point-of-care biosensors with direct applicability to primary healthcare delivery across Nigerian rural communities. Keywords: printed electrode, conductive polymer, biosensor, point-of-care diagnostics, rural healthcare