Redox‐Active Polyphenol Red Molecularly Imprinted Polymers on Porous Gold Electrodes for Ultrasensitive, AI‐Assisted Detection of Alzheimer's Biomarkers in Undiluted Biofluids

Early diagnosis of Alzheimer's disease (AD) is hindered by the high cost, complexity, and centralization of current diagnostic platforms such as enzyme-linked immunosorbent assay (ELISA) and single-molecule array (SIMOA). Here, an integrated point-of-care (PoC) biosensing platform is reported based on redox-active polyphenol red molecularly imprinted polymers (pPhR MIPs) deposited on highly porous gold (HPG) electrodes for the ultrasensitive, reagent-free detection of phosphorylated tau 181 (p-tau 181) in undiluted plasma and serum. The unique electrochemical interface combines the signal-enhancing properties of HPG with the redox functionality of pPhR, eliminating the need for external redox probes. The resulting sensor achieves a limit of detection (LOD) of 980 fg mL^-1 and sensitivity of 4.39 µA/(pg mL^-1), rivalling high-end lab-based assays while operating at a fraction of the cost. The platform integrates a low-cost, handheld potentiostat and a machine learning (ML)-enabled web app for real-time data classification and regression, achieving 100% classification accuracy with zero false positives or negatives. The system demonstrates compatibility with both ethylenediaminetetraacetic acid (EDTA) and heparin-treated samples and maintains accuracy in complex matrices. This work represents a step toward World Health Organization (WHO)-compliant, decentralized diagnostics for neurodegenerative disease, offering a scalable foundation for future multianalyte platforms targeting AD and related disorders.