A Scalable Spin-Coating Strategy for Mesoporous Gold Thin Films toward miRNA Detection

Mesoporous gold (mAu) films promise biosensing and electrochemical sensing due to their electroactive surface area, conductivity, and biocompatibility. However, conventional fabrication approaches, including electrodeposition and templating, often require substrate-specific processing and can be challenging to scale, limiting the broader integration of mAu films into practical sensing platforms. Here, we report scalable spin-coating of mAu films on transparent substrates with tunable thickness and uniform mesoporous framework. Electrochemical analyses reveal that additional coating cycles progressively increase the electrochemically active surface area and reduce the interfacial charge-transfer resistance, yielding a corresponding rise in the differential-pulse voltammetric signal, consistent with a mesoporous architecture that promotes efficient redox access and analyte adsorption. To demonstrate biosensing capability, a label-free electrochemical assay for the ovarian cancer-associated microRNA (miRNA) hsa-miR-200c-3p as a model target is developed. The sensor responds monotonically from 1 aM to 10 pM, with a linear calibration (R² = 0.9831), an LOD of 1.72 aM, and an LOQ of 2.98 aM without amplification. This study establishes spin-coating as a scalable approach to mesoporous Au electrodes for ultrasensitive nucleic acid biosensing. By decoupling mesoporous-metal fabrication from substrate conductivity, it enables high-surface-area electrodes on transparent, flexible, insulating supports and extension to RNA biomarkers for miniaturized point-of-care diagnostics; uniformity and long-term stability remain challenges.