This paper reports the development of a nonenzymatic, amplification-free, and sensitive platform for the detection of microRNA based on a new class of electrocatalytically active superparamagnetic gold-loaded nanoporous iron oxide nanocubes (Au@NPFe2O3NC). The assay showed an excellent detection sensitivity down to 100 fM and specificity towards the analysis of miR-21 in cell lines and tissue samples derived from patients with oesophageal squamous-cell carcinoma (ESCC).