Spectrophotometric and Electrochemical Determination of MicroRNA-155 Using Sandwich Hybridization Magnetic Beads

Here a new colorimetric assay and electrochemical biosensor for microRNA detection based on magnetic bead separation and enzyme amplification are reported. MicroRNA-155 was selected as a model because of its involvement in breast and lung cancer. A novel platform was developed for label-free microRNA detection based on a sandwich assembly using streptavidin magnetic beads coupled with a biotinylated capture probe that hybridized only a portion of the microRNA, the remainder hybridized with biotinylated detection probe linked to streptavidin-alkaline phosphatase. After appropriate reaction with the substrate, the enzymatic product was evaluated with colorimetric and electrochemical detection. The electrochemical method showed high sensitivity, allowing microRNA detection at 29 pmol L−1, which correspond to 1.4 fmole in 50 μL with a linear range from 81 pmol L−1 to 1.2 nmol L−1. This simple and efficient biosensor may have application in clinical molecular diagnostics and biomedical research.