A ratiometric fluorescence assay for bleomycin based on dual-emissive chameleon DNA-templated silver nanoclusters

Target-induced activation of DNAzyme for highly sensitive colorimetric detection of bleomycin via DNA scission

In this work, a label-free and sensitive colorimetric sensing strategy for the detection of bleomycin (BLM) was developed on the basis of BLM-mediated activation of G-quadruplex DNAzyme via DNA strand scission. A G-quadruplex based hairpin probe (G4HP) containing the scission site (5'-GT-3') of BLM at the loop region and guanine (G)-rich sequences at its 5'-end was employed in this protocol. In the presence of BLM, it may cleave the 5'-GT-3' site of the hairpin probe with Fe(ii) as a cofactor, releasing the G-tetrads DNA fragment, which may further bind hemin to form a catalytic G-quadruplex-hemin DNAzyme. The resultant G-quadruplex DNAzyme has notable peroxidase-like activity, which effectively catalyzes the oxidation of 2,2'-azino-bis(3-ethylbenzothiozoline-6-sulfonic acid) (ABTS) by H₂O₂ to produce the blue-green-colored free-radical cation (ABTS^·+). Therefore, the detection of BLM can be achieved by observing the color transition with the naked eye or measuring the absorbance at a wavelength of 420 nm using a UV-Vis spectrophotometer. Attributing to the specific BLM-induced DNA strand scission and the effective locking of G-tetrads in the stem of the G4HP, the colorimetric sensing strategy exhibits high sensitivity and selectivity for detection of BLM in human serum samples, which might hold great promise for BLM assay in biomedical and clinical research.

Copper ion and G-quadruplex-mediated fluorescent sensor for highly selective detection of bleomycin in actual samples

Improper dosage of Bleomycin (BLM) can easily lead to a series of side effects such as pulmonary fibrosis and pulmonary toxicity. Therefore, detecting the content of BLM in actual sample is very helpful to make full use of its therapeutic efficacy and reduce its toxicity. Herein, we constructed a copper ion and G-quadruplex mediated label-free sensor to detect BLM. The strategy mainly relies on the chelation of BLM to copper ions, which makes the copper ions lose the quenching ability to the fluorescent dye N-methylmesoporphyrin (NMM) after chelation. With the assistance of the G-quadruplex, the BLM content in the sample can be detected by observing the change in fluorescence. A good linear relationship can be clearly observed within the BLM concentration range of 0.1 nM-75 nM, and the limit of detection was derived as 0.1 nM. This sensor did not involve any labeling or addition of Fe²⁺, even in the presence of 10 different antibiotics and 11 different metal ions, it still has a good monitoring effect, and can be successfully applied to the detection of BLM in serum and wastewater. Thus, we believe that this work hold great potential in antibiotic monitoring and environmental protection.

A ratiometric fluorescence assay for bleomycin based on Cu2+-triggered cascade reactions and nanoparticle-mediated autocatalytic reactions

A new and facile method has been proposed for ratiometric fluorescence sensing of BLM based on the Cu²⁺-induced formation of two fluorescent probes (DFQ and DAP) with OPD as the precursor coupled with nanoparticle-mediated autocatalytic reactions.