Disposable microRNA biosensors based on dual-role polymer-dispersed silver nanowires for diagnosis of viral hemorrhagic septicemia virus infection in olive flounder

Fish farms often suffer from viral infections that can lead to mass mortality. Early detection of these infections can help prevent the spread of the infection. microRNA (miRNA) is a new biomarker for detecting early in-fections in farmed olive flounder. We developed a disposable miRNA biosensor by utilizing screen-printed carbon electrodes with polymer-dispersed silver nanowires (P-AgNWs). The target miRNA here was miR-15b-5p, which is considered a specific candidate for detecting viral hemorrhagic septicemia virus (VHSV) infection in fish. A capture probe (CP), a thiol-modified DNA oligonucleotide chain complementary to the miR-15b-5p, was immobilized on the surface of P-AgNWs. While the hybridization of miR-15b-5p with the CP is monitored using square wave voltammetry techniques based on the specific binding of methylene blue (MB) to the DNA-RNA hybrid formed between CP and the miR-15b-5p. The miRNA biosensor demonstrated a wide linear response range of 1.0-100 fM under optimum conditions with a low detection limit of 0.70 fM. According to a series of voltammetric experiments, the approach demonstrated acceptable precision and sensitivity for determining the miR-15b-5p levels in olive flounder infected with VHSV.