ctDNA detection using the ID ring scheme with hyperbranched RCA and a fluorescent color. A. Schematic illustration of the ctDNA detection using the ID ring scheme with hyperbranched RCA and a fluorescent color. B, C, D, E. Histograms with an error bar of fluorescence intensity at 530 nm of different ctDNA ratios of KRAS, NRAS, PIK3CA and BRAF, respectively. Each column bar represents the average value of three independent assays with error bars indicated. *P < 0.05, **P < 0.01, ***P < 0.001. The inset is the image of the corresponding fluorescence spectra from 515 to 650 nm.