Gene

Catalysis

Molecular biology

Biology

Chromatography

Biochemistry

Aptamer

Rolling circle replication

Biosensor

Combinatorial chemistry

Exonuclease III

Complementary DNA

Kanamycin

Exonuclease

Escherichia coli

Protamine

Chemistry

Selectivity

Biophysics

Detection limit

DNA polymerase

Heparin

Food Chemistry

A label-free colorimetric method based on exonuclease I (Exo I)-assisted signal amplification with protamine as a medium was developed for analysis of kanamycin. In this study, a double-stranded DNA (dsDNA) probe was tailored by manipulating an aptamer and its complementary DNA (cDNA) ensuring detection of target with high selectivity and excellent sensitivity. Herein, protamine could not only combine with negatively charged gold nanoparticles but also interaction with polyanion DNA. Upon addition of target kanamycin, the target-aptamer complex was formed and the cDNA was released. Thus, both aptamer and cDNA could be digested by Exo I, and the captured kanamycin was liberated for triggering target recycling and signal amplification. Under optimized conditions, the proposed colorimetric method realized a low detection limit of 2.8 × 10−14 M along with a wide linear range plus excellent selectivity. Our strategy exhibited enormous potentials for fabricate various kinds of biosensors based on target-induced aptamer configuration changes.

Label-free exonuclease I-assisted signal amplification colorimetric sensor for highly sensitive detection of kanamycin