An impedance-based biosensor was developed to detect miRNA-206, associated with Alzheimer's disease, with remarkable sensitivity (LOD 0.15 aM). By modulating surface coverage and hybridization efficiency, the biosensor achieved a reduced dielectric constant and smaller association constant between miRNA capture-target. This phenomenon enhanced the biosensors’ dynamic range (μM to aM), while maintaining high selectivity, low non-specific binding, and sensing phase stability. The biosensor was also validated in the clinical settings by accurately quantification of miRNA-206 in real plasma samples. To enhance biosensor sensitivity, miRNA reporter-probes were modified with gold nanorods (AuNRDs).The study employed chronoamperometry analysis, emphasizing hydrogen peroxide reduction by gold nanorods confined to the gold electrode via miRNA target hybridization. Optimization steps, including [miRNA reporter-probe]I to [AuNRDs] ratios, optimal hydrogen peroxide concentration for electrocatalysis, and refinement of target—reporter-probe hybridization time, improved detection accuracy. The biosensor detected miRNA-206 across a broad dynamic range (fM to μM) with high sensitivity (LOD 0.46 fM), selectivity against base mismatches, and rapid response time (5 to 25 minutes). Screen printed carbon electrodes (SPCE) offered a cost-effective and biocompatible alternative for mass-producing miRNA detection platforms. Two SPCE, containing different gold structures within their carbon ink as 10%(w/w) microflakes (AuF) and 10%(w/w) microspheres (AuS), were developed. Comparative analysis involving chronoamperometry revealed that SPCEs with AuS exhibited superior charge transfer process, higher peak currents and reduced potential for hydrogen peroxide reduction. Further assessments evaluated SPCE with an enhanced sensing phase (i.e. 20% (w/w) AuS). An additional of 10% AuS onto the matrix ink led to an expressive (i.e 56-fold) signal amplification of the platform when using AuNRDs as labels. In a proof-of-concept study, the innovative 20% (w/w) AuS SPCE demonstrated its potential as a multiplex platform. It successfully detected potential biomarkers for Alzheimer disease (miRNA-206) and epilepsy (let-7b and miRNA-135a) using various nanomaterial labels. Platinum nanoparticles showed the highest electrocatalytic activity, followed by PdNCBs and AuNRDs, catering to different miRNA requirements. The biosensor exhibited a wide dynamic range (fM-uM), ultralow LODs (fM), high selectivity against mismatches and stable sensing phase. The successful detection of multiples miRNAs and absence of cross-reactivity between assays position it as a promising candidate for multiplexed analysis.