A Cascade Signal Amplification Strategy for the Ultrasensitive Fluorescence Detection of Cu²⁺ via λ-Exonuclease-Assisted Target Recycling with Mismatched Catalytic Hairpin Assembly.

ABSTRACT: Herein, an ultrasensitive DNAzyme-based fluorescence biosensor for detecting Cu²⁺ was designed using the cascade signal amplification strategy, coupling λ-exonuclease-assisted target recycling and mismatched catalytic hairpin assembly (MCHA). In the designed detection system, the target, Cu²⁺, can activate the Cu²⁺-dependent DNAzyme to cause a cleavage reaction, releasing ssDNA (tDNA). Then, tDNA binds to hairpin DNA (H0) with an overhanging 5'-phosphorylated terminus to form dsDNA with a blunt 5'-phosphorylated terminus, which activates the dsDNA to be digested by λ-Exo and releases tDNA along with another ssDNA (iDNA). Subsequently, the iDNA initiates MCHA, which can restore the fluorescence of carboxyfluorescein (FAM) previously quenched by tetramethylrhodamine (TAMRA), resulting in a strong fluorescent signal. Furthermore, MCHA efficiently improves the signal-to-noise ratio of the detection system. More importantly, tDNA recycling can be achieved with the λ-Exo digestion reaction to release more iDNA, efficiently amplifying the fluorescent signal and further improving the sensitivity to Cu²⁺ with a detection limit of 60 fM. The practical application of the developed biosensor was also demonstrated by detecting Cu²⁺ in real samples, proving it to be an excellent analytical strategy for the ultrasensitive quantification of heavy metal ions in environmental water sources.

SUBMITTER: Liu Z 

PROVIDER: S-EPMC10605925 | biostudies-literature | 2023 Oct

REPOSITORIES: biostudies-literature