Journal
BIOSENSORS-BASEL
Volume 13, Issue 10, Pages -Publisher
MDPI
DOI: 10.3390/bios13100918
Keywords
Cu2+ detection; lambda-exonuclease-assisted target recycling; mismatched catalytic hairpin assembly; cascade signal amplification; environmental pollutant
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An ultrasensitive DNAzyme-based fluorescence biosensor for detecting Cu2+ was designed using cascade signal amplification strategy. The detection system utilized the activation of Cu2+-dependent DNAzyme by Cu2+ and subsequent reactions to generate a strong fluorescent signal. The biosensor showed excellent detection performance and potential applications.
Herein, an ultrasensitive DNAzyme-based fluorescence biosensor for detecting Cu2+ was designed using the cascade signal amplification strategy, coupling lambda-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 lambda-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 lambda-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.
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