Controlled self-assembly of gold nanoparticles on indium tin oxide: Tuning electron transfer and reproducibility for electrochemical aptasensor interface design

A systematic study was conducted to relate gold nanoparticle (AuNP) loading–dependent film morphology on indium tin oxide (ITO) to electron-transfer characteristics and electrochemical signal reproducibility for aptasensor interface design. AuNPs were electrostatically immobilized on amine-functionalized ITO substrates to provide Au S anchoring sites for thiolated DNA aptamers, enabling target-general electrochemical transduction. Combined scanning electron microscopy and square-wave voltammetry revealed that AuNP concentration critically determined film morphology, charge-transport pathways, and measurement dispersion. An intermediate AuNP concentration of 1.0 mM produced the most uniform coverage, minimized charge-transfer resistance surrogates, and yielded the narrowest distribution of SWV peak currents, reflecting reduced coverage-induced heterogeneity while preserving conductive connectivity. In contrast, insufficient (0.5 mM) or excessive (3.0 mM) nanoparticle deposition caused incomplete coverage or aggregation, resulting in attenuated electrochemical response and elevated coefficients of variation. The optimized AuNP/ITO electrodes also exhibited stable, reproducible current attenuation upon aptamer–cell interaction, confirming their suitability as robust electrochemical aptasensor interfaces. These findings establish quantitative design principles for nanostructured AuNP/ITO conductive interfaces by identifying an intermediate coverage regime that maximizes current stability across repeats and supports reliable aptamer-based sensing.