Ultrasensitive sensing platform based on Au 0.1 FeCoNiCu high-entropy alloy nanoparticle-DNA walker dual signal amplification for electrochemical detection of miRNA-21

Overcoming the critical limitation of poor sensitivity in electrochemical biosensors for early breast cancer diagnosis, this study presents an innovative approach. We developed a robust coordination strategy, utilizing serine-functionalized graphene quantum dot (SGQD), to synthesize Au _0.1 FeCoNiCu high-entropy alloy nanoparticles (HEA NPs). The resulting Au _0.1 FeCoNiCu HEA NPs (32 ± 1.7 nm) exhibit a single FCC phase, elemental homogeneity, and graphene surface modification. This unique structure confers significantly enhanced catalytic activity (> 12-fold higher than pure Au NPs) and superior affinity towards polar electrolytes. Furthermore, we integrated these HEA NPs with a DNA walker circuit to construct a novel electrochemical biosensor for ultrasensitive miRNA-21 detection. Target miRNA-21 triggers the DNA walker, immobilizing ferrocene molecules on the electrode surface and generating a measurable electrochemical signal. This dual-amplification strategy (HEA NP catalysis + DNA walker) achieved unprecedented sensitivity: a linear current response (at 0.22 V) over an extraordinary range (1×10⁻²⁰ M to 1×10⁻¹⁵ M) and a record-low detection limit of 3.4×10⁻²¹ M. This represents a 2–3 orders of magnitude sensitivity improvement over state-of-the-art sensors, successfully demonstrated in serum analysis.