Multivalent copper nanospheres with efficient molecular oxygen activation to remarkably enhance electrochemiluminescence of luminol/dissolved O2 system for biosensing assay

Abstract

Herein, multivalent copper nanospheres (Cu NSs) with efficient molecular oxygen activation are presented as a novel co-reaction accelerator in the luminol/dissolved O2 electrochemiluminescence (ECL) system. This advancement significantly enhances ECL emission, combined with a highly efficient target conversion cascade amplification strategy to construct a “signal-on” type ultrasensitive biosensor for microRNA-21 (miRNA-21) detection. Intriguingly, the multivalent Cu NSs as co-reaction accelerators expedite the activation of dissolved O2, generating reactive oxide species (ROS) without electro-excitation. This process markedly boosts the ECL intensity, thereby improving detection sensitivity. In addition, incorporating a target conversion cascade amplification strategy enables the conversion of trace amounts of target miRNA-21 into abundant mimic targets. These mimic targets then assemble into a dendritic DNA nanostructure, facilitating the efficient immobilization of a copious amount of the ECL emitter, doxorubicin-luminol (Dox-Lum), further enhancing the sensitivity of the biosensor. Consequently, the developed biosensor achieves highly sensitive detection of miRNA-21, demonstrating a low detection limit of 59 aM. It was preliminarily applied to determine miRNA-21 in lysates from tumor cells. This strategy introduces a negative voltage-free co-reaction accelerator, significantly amplifying the ECL signal in a ternary ECL system, and offers a promising analytical method for early clinical diagnosis.