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In this work, we proposed a strategy that combined molecularly imprinted polymers (MIPs) and hybridization chain reaction into microfluidic paper-based analytical devices for ultrasensitive detection of target glycoprotein ovalbumin (OVA). During the fabrication, Au nanorods with a large surface area and superior conductibility were grown on paper cellulosic fiber as a matrix to introduce a boronate affinity sandwich assay. The composite of MIPs including 4-mercaptophenylboronic acid (MPBA) was able to capture target glycoprotein OVA. SiO2@Au nanocomposites labeled MPBA and cerium dioxide (CeO2)-modified nicked DNA double-strand polymers (SiO2@Au/dsDNA/CeO2) as a signal tag were captured into the surface of the electrode in the presence of OVA. An electrochemical signal was generated by using nanoceria as redox-active catalytic amplifiers in the presence of 1-naphthol in electrochemical assays. As a result, the electrochemical assay was fabricated and could be applied in the detection of OVA in the wide linear range of 1 pg/mL to 1000 ng/mL with a relatively low detection limit of 0.87 pg/mL (S/N = 3). The results indicated that the proposed platform possessed potential applications in clinical diagnosis and other related fields.

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An electrochemiluminescence (ECL) biosensor is described for the detection of microRNA (miRNA-155) based on tris(bipyridine)ruthenium(II) functionalized metal organic framework (RuMOF) materials. The material was prepared by a solvothermal method and was found to be stable even in acidic solution. However, it is selectively and sensitively disassembled by Hg(II) ions, resulting in the release of large quantities of Ru(II)(bpy) ions, which produces a strong ECL signal. In view of the ion-selective disassembly and release and strand displacement process, an ultrasensitive ECL sensing method was established for detection of microRNAs. In the presence of the target, the hairpin structure of H1 can open and hybridize with the hairpin probe H2 to form a more stable H1-H2 duplex structure than the H1-target hybrid. The target of hybridization to H1 was immediately freed from the structure and the released target re-entered the new hairpin assembly target recovery process. The remaining H2 single fragment can bind to the I-RuMOFs-conjugates. The more hairpin probes H1, the more I-RuMOFs-conjugates load the DNA fragments, leading to the signal amplification. The method works in the 0.8 f. to 1.0 nM miRNA-155 concentration range and has a detection limit of 0.3 fM. The assay is sensitive, fairly specific and remarkably stable. In our perception, it offers an attractive tool for the sensitive detection of microRNAs in clinical samples. Graphical abstract An electrochemiluminescence (ECL) based biosensor is described for the detection of microRNA (miRNA-155) based on the use of a metal organic framework functionalized with ruthenium(II)tris(bipyridine) that was deposited on a glassy carbon electrode (GCE) modified with gold nanoparticles.