Size-Dependent Electrochemical Response and Dopamine Sensitivity of Aptamer-Modified Printed Gold Nanoparticle...

We report a comparative evaluation of dopamine (DA) sensing using gold nanoparticle (AuNP)-based electrodes fabricated from precursor-free aqueous suspension through atmospheric plasma-assisted printing. In this study, electrodes printed from 20, 40, and 80 nm AuNPs in aqueous suspension were analyzed to establish correlations between nanoparticle size, surface morphology, and dopamine redox performance. Morphological and optical characterization of the printed structures confirmed the preserved nanoscale morphology and stable electrochemical behavior. Electrochemical analysis revealed stable, size-dependent redox behavior for the printed electrodes and long-term stability over 100 cycles. Electrodes printed from smaller nanoparticles (20 nm) exhibited reduced ΔE values and faster electron-transfer kinetics, while intermediate-sized electrodes (40 nm) offered the most balanced combination of electroactive surface area, morphological stability, and charge-transfer efficiency. In contrast, larger nanoparticle-derived electrodes (80 nm) had lower surface area, resulting in diminished redox reversibility and sensitivity. Aptamer functionalization followed by thiol backfilling enhanced dopamine selectivity and sensitivity across 1-100 μM, achieving micromolar detection limits and excellent reproducibility. This clean, scalable approach provides a robust foundation for printing low-cost, flexible biosensors capable of selective detection and future integration into wearable diagnostic platforms.