It remains a huge challenge to integrate the sensitivity, stability, reproducibility, and anti-fouling ability of electrochemical biosensors for practical applications. Herein, we propose a self-assembled electrode combining hexanethiol (HT), poly-adenine (poly-A), and cholesteryl-modified DNA to meet this challenge. HT can tightly pack at the electrode interface to form a hydrophobic self-assembled monolayer (SAM), effectively improving the stability and signal-to-noise ratio (SNR) of electrochemical detection. Cholesteryl-modified DNA was immobilized at the electrode through the hydrophobic interaction with HT to avoid the competition between the SAM and the DNA probe on the gold site. Thus, the assembly efficiency and uniformity of the DNA probe as well as the detection reproducibility were increased remarkedly. Poly-A was added on the HT assembled electrode to occupy the unreacted sites of gold to further enhance the anti-fouling ability. The combination of HT and poly-A allows the electrode to ensure favorable anti-fouling ability without sacrificing the detection performance. On this basis, we proposed a dual-signal amplification electrochemical biosensor for the detection of exosomal microRNAs, which showed excellent sensitivity with a detection limit down to 1.46 aM. Importantly, this method has been successfully applied to detect exosomal microRNA-21 in cells and human serum samples, proving its potential utility in cancer diagnosis.
Two-dimensional conductive metal–organic frameworks (2D c-MOFs) hold great promise for electrochemical applications due to their π-conjugated structures and high conductivity, but their application in electrochemiluminescence (ECL) sensing remains largely unexplored. In this study, we synthesized 2D c-MOF Cu3(benzenehexathiol) nanosheets (CuBHT NSs) with lateral dimensions of 2–10 μm and a thickness of 24 nm and immobilized them on indium tin oxide (ITO) electrodes. This platform facilitated the first study of luminol’s cathodic ECL behavior. CuBHT NSs exhibited exceptional oxygen reduction reaction (ORR) catalytic activity, significantly enhancing the generation of reactive oxygen species (ROS) and thereby increasing the luminol’s cathodic ECL response. Mechanistic studies confirmed that unsaturated Cu sites in CuBHT play a crucial role, as Uric acid (UA) can bind to unsaturated Cu sites, inhibiting ROS production. This outcome enabled a highly sensitive and selective ECL sensor for UA with a wide linear range (10 nM–0.1 mM) and a low detection limit (3.5 nM, S/N = 3). The sensor was successfully applied to detect UA in serum samples.
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