Carbon quantum dots@metal-organic framework based catalytic nucleic acid fluorescent system for highly sensitive and selective detection of Pb2+ in aqueous solutions

Accumulation of heavy metal ions in the ecosystem has become a major concern due to their adverse impacts on animals, humans, and aquatic habitats. The development of a rapid and portable sensing system is important for the prompt detection and proper management of such pollutants. Herein, we have designed a fluorescence-based biosensor for the selective and sensitive detection of Pb2+ ions using a DNAzyme system that is active only in the presence of lead (II) ions (Pb2+). The developed nanoprobe relies on two major components: (i) boron and nitrogen carbon dots (BNCDs)-doped carboxyl functionalized-terbium metal-organic framework (COOH-Tb MOF) as a fluorescent tag and (ii) quencher-modified catalytic NH3-GR5 DNAzyme as a bioreceptor molecule. The fluorescent tag (BNCDs/MOF) exhibits dual fluorescence with emission peaks located in the regions of blue and green. In the absence of Pb2+ ions, this hybridization undergoes reduced emission intensity because of the overlap in fluorescence emission between BNCDs@Tb-MOF and quenchers. However, as the catalytic core of the DNAzyme strand is activated in the presence of Pb2+ ions, the fluorescent emission of BNCDs/Tb-MOF resumes with the cleavage of quencher-tagged substrate strand. Here, the release of a shorter oligo sequence effectively increases the intensity of the proposed novel biosensor to realize low level detection of Pb2+ (e.g., to 0.96 ppb in a wide detection range from 2 to 1000 nM). The establishment of this novel biosensing approach is expected to offer new insights into rapid, selective, and sensitive detection of major pollutants for food and environmental safety.

Automated summary

Accumulation of heavy metal ions in the ecosystem is a major concern for their negative effects on animals, humans, and aquatic habitats. A rapid and portable sensing system is crucial for detecting and managing such pollutants. A fluorescence-based biosensor has been developed for the selective and sensitive detection of Pb2+ ions using a DNAzyme system that responds only to the presence of lead (II) ions (Pb2+). This novel biosensing approach offers insights into the rapid and sensitive detection of major pollutants for food and environmental safety.