Near-infrared electrochemiluminescence of carbon nitride quantum dots for ultrasensitive microRNA assay

Herein, carbon nitride quantum dots (CNQDs) with efficient near-infrared electrochemiluminescence (NIR-ECL) and excellent biocompatibility were prepared as an emitter to construct an ultrasensitive regenerative biosensing platform for detection of microRNA-222 (miRNA-222). Impressively, the introduction of electron-rich pyrimidine effectively increased the conjugation effect of electrons on triazine ring in CNQDs to result in red shift of ECL emission wavelength from 483 nm to 690 nm with the increase of pyrimidine. Meanwhile, an improved circular DNA walker was assembled by the catalytic ligation of T4 DNA ligase instead of traditional base complementary pairing, which enhanced the stability of circular DNA walker to increase walking efficiency. Based on CNQDs as emitter and circular DNA walker as signal amplifier, a regenerative biosensor platform was prepared to achieve the ultrasensitive detection of miRNA-222 with the limit of detection of 2.39 aM and it was successfully applied for sensitive detection of miRNA-222 in the lysate of cancer cells. This work opened a promising road for synthesizing efficient NIR-ECL CNQDs to reduce damage to organisms and achieve deeper tissue penetration and provided a new method for biomarker detection and disease diagnosis.