A ratiometric lanthanide-free fluorescent probe based on two-dimensional metal-organic frameworks and carbon dots for the determination of anthrax biomarker.

Abstract

Alanthanide-free fluorescent probe has been constructed for the first timebased on two-dimensional metal-organic frameworks (2D MOFs) and carbon dots (CDs) for ratiometric determination of dipicolinic acid (DPA), the biomarker of Bacillus anthracis. The fluorescence intensity at 659nm increased due to the release of organic ligands TCPP resulting from the selective interaction between DPA and Zn2+ of 2D MOFs. CDs provided a reference signal at 445nm which was almost unaffected, realizing self-calibration DPA sensing. F659/F445 versus the concentration of DPA shows good linear relationships in the range 0.01-0.2μM and 0.2-10μM under 390-nm excitation, with adetection limit of 7nM. The ratiometric probe was prepared from 2D lanthanide-free MOFs so that the drawbacks of lanthanide-based probes were overcome. The proposed sensing system was successfully applied to the determination of DPA in spiked biological samples. These results suggest that a novel, simple, and selective strategy of determining DPA with 2D lanthanide-free MOFs is implemented. Graphical abstract Zn-TCPP nanosheets and a blue carbon dots (b-CDs) are synthesized to construct the ratiometric probe, which can exhibit fluorescence at 445and 659nm with 390-nm excitation. Dipicolinic acid (DPA) can deprive the junction ions of Zn-TCPP nanosheets, triggering the collapse ofZn-TCPP nanosheets. The fluorescence at 659nm is enhanced due to the release of TCPP, while the peak of b-CDs at 445nm is almost not affected. Thus, the fluorescence intensity ratio (F659/F445) can serve as the response signal for sensitive DPA sensing.