Dual-signal ratiometric electrochemiluminescence assay for detecting the activity of human methyltransferaseElectronic supplementary information (ESI) available. See DOI: 10.1039/c8an00611c

In this paper, a dual-signal ratiometric electrochemiluminescence (ECL) assay was developed to detect human DNA (cytosine-5)-methyltransferase1 (DNMT1) activity. Mercaptopropionic acid (MPA)-modified Eu 3+ -doped CdS nanocrystals (MPA-CdS:Eu NCs) and luminol were used as two different ECL emitters, which showed ECL signals at different electrochemical potentials. The resultant ECL peaks exhibited opposite trends in the DNMT1 system. According to the ratio of the ECL responses of CdS to luminol, the DNMT1 activity was detected in the range of 1.0-30.0 U mL −1 in buffer solution. The limit of detection (LOD) was estimated to be 0.07 U mL −1 at a signal-to-noise ratio of 3. The assay was extended to detect the DNMT1 activity from crude lysates of cancer cells, along with the effect of DNMT1 inhibitors such as 5-aza and 5-aza-2′-dC. A ratiometric electrochemiluminescence assay using CdS:Eu NCs and luminol as signal emitters was fabricated for detecting the human methyltransferase activity.