The carbon dots with near-infrared electrochemiluminescence emission and low excitation potential for ultrasensitive analysis of microRNA-222

In this work, nitrogen and sulfur codoped near-infrared emission carbon dots (N,S-NIR-CDs) were used as neoteric electrochemiluminescence (ECL) emitters with high efficiency to construct a biosensor for ultrasensitive analysis of microRNA-222 (miRNA-222), which has been regarded as prospective biomarkers for early cancer diagnosis. Impressively, compared to conventional CDs with short ECL wavelength and large excitation voltage, N,S-NIR-CDs possessed wide sp domains and narrow band gap, leading to the near-infrared ECL emission at 680 nm and low excitation potential from −1.0 to 0 V, which not only decreased the photochemical damage for biomolecules but also reduced the side reaction. Moreover, an improved T7 Exonuclease induced cascade amplification (EICA) strategy was designed to transform trace miRNA-222 into plentiful output DNA in dual-cycle for greatly improving the target conversion efficiency. Therefore, by combining the N,S-NIR-CDs as neoteric ECL emitters and EICA strategy as signal amplifier, the constructed ECL biosensor could realize the ultrasensitive analysis of miRNA-222 with a identification limit of 5.65 aM and successfully employed in miRNA-222 analysis from liver cancer cell (HCCLM3 and MHCC-97L) lysate. This strategy developed a kind of neoteric CDs with NIR ECL emission and low excitation potential to establish a highly efficient biosensor for biomarker analysis, which prepared a road for early diseases diagnosis and lied a foundation for biological ECL imaging.