AuNPs/CdS QDs/CeO2 ternary nanocomposite coupled with scrollable three-dimensional DNA walker mediated cycling amplification for sensitive photoelectrochemical miRNA assay.

Herein, a novel ternary nanocomposite (AuNPs/CdS QDs/CeO2) with excellent photoelectrochemical (PEC) performance was synthesized as signal probe to construct a near-zero background biosensor for sensitive miRNA-182-5p detection, by integrating with a scrollable three-dimensional (3D) DNA walker mediated cleavage cycling amplification. Impressively, the formation and rolling of scrollable 3D DNA walker triggered by target could realize dynamic, rapid and specific digestion of hairpin DNA on electrode with the aid of Exonuclease III (Exo III), which thus exposed abundant binding sites for assembling stable DNA labeled AuNPs/CdS QDs/CeO2 nanoprobes. Thanks to the formation of type-II heterojunction (between CeO2 and CdS QDs) and Schottky junction (generated by CeO2 and AuNPs), an ideal photoelectric conversion efficiency accompanied with stunningly improved photocurrent was thus acquired for significantly improving the detection sensitivity. It turned out that the detection limit (LOD) of biosensor was ultralow (31 aM). Significantly, the proposed PEC biosensor would exhibit great potential for the composite as a splendid indicator and provide an avenue for constructing the sensing platform with excellent sensitivity and ultralow background.