Multiplexed Ratiometric Detection of Key Biomarkers by Lanthanide-Integrated Carbon Dots and Their Bioimaging Applications

Abstract

The development of advanced fluorescent probes for simultaneous biomarker detection is in critical demand nowadays in the field of analytical chemistry and biomedical research. However, the co-existence of multiple biomarkers in a complex microenvironment heavily compromises the performance of a sensor. A promising solution lies in the rational design of smart ratiometric fluorescent probes for multiplexed detection which not only offers simplified and cost-effective methods but also improves the accuracy and reliability of the probe as a diagnostic tool. Therefore, carbon dots were integrated with lanthanides metal ions to construct two unique dual emissive probes: Zn-CD@Eu and CD@Tb which were successfully employed for simultaneous and ratiometric detection of important biomarkers. Zn-CD@Eu was utilized for detection of dipicolinic acid (DPA), uric acid (UA) in two emission channels, blue (λem = 437 nm) and red (λem = 616 nm), where DPA showed a turn-on red emission with turn-off blue emission (LOD = 0.53 μM). When exposed to this system, UA showed a turn-off red emission with turn-on blue emission (LOD = 0.36 μM). Similarly, CD@Tb was utilized for detection of epinephrine (EP) and pyrophosphate anion (PPi) in blue (λem = 405 nm) and green (λem = 545 nm) emission channels, where EP displayed a turn-on blue emission with turn-off green emission and PPi displayed a turn-on green emission while quenching the blue emission. Bioimaging ability of Zn-CD@Eu was explored in an invertebrate model, Drosophila melanogaster (common fruit fly), where the Malpighian tubules of the organism was chosen as a choice of organ for ex vivo visualization of uric acid because of its similarities to human kidney. Further, CD@Tb was employed as an imaging tool of epinephrine and pyrophosphate in SH-SY5Y and NIH 3T3 cells respectively. This work highlights the potential and versatility of the carbon dot-based sensors as water-soluble, biocompatible tools for multiplex biomarker detection.