Fluorometric detection: Two DNA sequences were designed to construct the probe: one was modified with BHQ-1 at the 3' terminal, and the other one with FAM at the 5' terminal. The two DNA solutions (10 μM stock solution) were mixed at room temperature for 1 h to prepare the F-Q probe. For detection of RCA products, 10 μL of the F-Q probe was added into 30 μL of amplification products and 60 μL H2O. The mixture was kept at room temperature for 45 min.