Abstract:
Electrochemical biosensors are widely used in clinical diagnostics, but commercial substrates that meet reproducibility requirements cost several U.S. dollars per electrode, placing both point-of-care deployment and high-throughput biosensor research out of reach. Printed circuit board (PCB) electrodes with an electroless nickel/immersion gold (ENIG) finish offer the same surface metal at a fraction of the cost but suffer from electrode-to-electrode variability driven by the thin commercial gold finish. We report a two-step cleaning and conditioning protocol that brings independently prepared ENIG-PCB electrodes to a single, reproducible electrochemical baseline. Multimodality surface characterization (X-ray photoelectron and scanning electron microscopy (SEM), contact angle, and stylus profilometry) confirms removal of the contaminant overlayer and reduction of nickel-oxide character. Across an independently prepared cohort of N = 49 cleaned electrodes, the charge-transfer resistance averages 45.43 plus-minus 2.67 Omega with a coefficient of variation of 5.88 percnet. Across a 20-fold concentration range of the ferri-/ferrocyanide redox probe, the cleaned platform reproduces the diffusion-controlled Randles-Sevcik scaling (Ipa is proportional to C sup(1.01), R sup(2) = 0.999) and peak symmetry (|Ipa/Ipc| =1.03 plus-minus 0.02 and N = 12) characteristic of standard polycrystalline-gold electrodes. As a proof of concept, a sandwich-format Beta -hCG (Beta -human chorionic gonadotropin) immunoassay on the cleaned platform yields a signal-to-noise ratio of 30 relative to the blank. The per-electrode substrate cost is approximately 6.8 (<| 10), enabling both clinical deployment and biosensor method development on a commercially scalable substrate.
