Procedure: Streptavidin-magnetic bead suspension (50 µL) was transferred into a vial. The beads were washed twice by the binding/washing buffer and then re-suspended in 100µL of the buffer. A biotin-LNA-modified probe (5×10^-4 mol/L, 5 µL) was added. The mixture was placed in a shaker at 37 °C for 30 min. Magnetic beads were then collected and washed three times with the binding/washing buffer to remove any unbound biotin in the LNA-modified probe. The conjugate collected was re-suspended in a 1.0 mL binding/washing buffer. miRNA-21-containing sample solution (1nM or 50nM, 100 µL) was added to LNA-modified probe-magnetic bead conjugate suspension (200 µL). The mixture was incubated at 37 °C for 30 min to complete the hybridization.