Rapid‐Forming Conductive Antifouling Hydrogel Coating Enables Magnetically Guided Electrochemical POCT for Direct at‑Home Blood Testing

Electrochemical point-of-care testing for complex clinical samples is frequently hampered by matrix interference, signal instability, and laborious electrode modification procedures. Herein, we report a magnetic portable electrochemical immunosensor utilizing a conductive, anti-fouling hydrogel coating composed of sodium alginate, polyethylene glycol, and graphene (SPG). Upon calcium-ion triggering, the SPG solution forms a stable electrode hydrogel coating within 1 min, effectively resisting nonspecific adsorption while maintaining low‑impedance electron transfer. Guided by a 3D-printed magnetic apparatus, the MpECis directly captures target-bound magnetic complexes, enabling rapid enrichment and electrical readout within 25 min. By implementing time‑domain averaging over the enzymatic reaction plateau, the coefficient of variation of electrical signals generated by nanoenzyme catalysis was reduced to 3.4%, markedly improving measurement reproducibility. The clinical practicality of the SPG MpECis platform was validated through three independent cohorts, including detection of cardiac troponin I in 59 serum samples, quantification of extracellular vesicles in 47 plasma samples, and detection of C-reactive protein in 17 fingertip blood samples. Compared with the reference method, the area under the curve of this method are 0.99, 0.93, and 1.00, respectively. This platform offers a practical route for stable electrochemical diagnostics in complex biological matrices and home-based precision medicine.