“…The correlation equation is ΔF¼59.45þ 65.97 log C with a correlation coefficient of 0.9872. The detection limit was calculated to be 200 pM (3s/k, where s is the relative standard deviation and k is the slope of the calibration graph, n ¼11), providing superior detection sensitivity compared with aptamer-based fluorescence strategies (Sanghavi et al, 2013;Xu et al, 2014;Zhang et al, 2012), and it is comparable with the T4 DNA-based strategies (Ma et al, 2012(Ma et al, , 2013. The high sensitivity can be achieved owing to the following factors: (1) T4 DNA ligase can efficiently help the formation of the super-sandwich in the homogeneous solution and (2) an 800-1000 fold increase of the fluorescence intensity of SG I can be obtained when it is intercalated into the duplex DNA while the formed super-sandwich can provide more binding points for the dye.…”