Zn2GeO4:Mn Luminescent Superparticles/Au-Ag Bimetallic Nanoarrays for ECL Detection of miRNA-156a in Ginseng Exosomes

MicroRNA (miRNA) in plant exosomes exhibits cross-species regulatory properties, opening a new avenue for researching natural pharmacodynamic molecules. In this study, a novel biosensing system has been developed based on Zn2GeO4:Mn luminescent superparticles/Au-Ag bimetallic nanoarrays for the detection of miRNA-156a in ginseng. First, polyoxyethylene-polyoxypropylene-polyoxyethylene (PEO-PPO-PEO) triblock copolymer (P123) is used as a structure-directing agent to induce the directional self-assembly of Zn2GeO4:Mn nanorods as luminescent superparticles (SPs). Moreover, the hydrophilic end of P123 adsorbs more coreactants to accelerate reaction kinetics and significantly boosts the intensity and stability of electrochemiluminescence (ECL). Meanwhile, a Au-Ag bimetallic nanoarray is fabricated as an electrode modification interface. This Au-Ag bimetallic nanoarray enlarges the electrochemical surface area and elevates electron-transfer rates, leading to remarkable ECL signal enhancement. Furthermore, the high catalytic activity of Ag lowers the energy barrier for the electrochemical reaction in the system, thereby enabling the ECL reaction to proceed at a lower negative potential. Finally, a sandwich-type ECL biosensor is constructed for the detection of miRNA-156a in ginseng exosomes. The sensor has a linear range of 1 fM to 1 nM and a limit of detection (LOD) as low as 1.3 fM, which offers technical support for the pharmacodynamic evaluation and medicinal part selection of ginseng.