A novel self-enhancement NCNDs-BPEI-Ru nanocomposite with highly efficient electrochemiluminescence as signal probe for ultrasensitive detection of MTB

Abstract

Herein, a novel self-enhanced Ru(Ⅱ)-based nanocomposite (NCNDs-BPEI-Ru), synthesized by covalently connecting nitrogen-doped carbon nanodots (NCNDs) and tris (4,4′-dicarboxylicacid-2,2′-bipyridyl) ruthenium (II) dichloride (Ru(dcbpy)3Cl2) through branched polyethyleneimine (BPEI), could be used as an electrochemiluminescence (ECL) signal probe for ultrasensitive detection of mycobacterium tuberculosis (MTB) DNA fragment. Without any extraneous coreactants, NCNDs-BPEI-Ru could generate an ultra-strong initial ECL signal on the glassy carbon electrode (GCE) (signal-on) due to the coreaction from BPEI and NCNDs to Ru(dcbpy)3Cl2. Then, self-assembled DNA nanotubes embedding methylene blue molecules (MB-DNANTs) were modified on the nanocomposite to effectively quench the ECL intensity of NCNDs-BPEI-Ru owing to the quenching effect of MB for Ru(dcbpy)3Cl2 (signal-off). Finally, the 3D DNA nanomachine, formed by a DNA-functionalized magnetic beads (DNA-MBs) could transform trace target MTB into massive output DNA, and the MB-DNANTs could be disintegrated to get ECL signal recovery (signal-on) due to hybridization of output DNA and the S2 in DNANTs. Therefore, the proposed biosensor exhibited predominant performance for the detection of MTB DNA fragment with a low detection limit of 1.4 aM, which showed great application value in the detection of biomarkers in clinical diagnosis.