Streptomycin-Triggered Suppression of G-Quadruplex/Hemin DNAzyme Activity: A Rapid Label-Free Colorimetric Strategy for Food Safety Monitoring

A rapid, simple, and stable detection method for streptomycin has been established based on the coloration reaction of 3,3′,5,5′-tetramethylbenzidine (TMB) catalyzed by peroxidase-mimicking DNAzymes (PMDs). It is discovered that the catalytic activity of PMDs constructed with G-quadruplex and hemin is weakened in the presence of streptomycin. In the presence of streptomycin, the OD 450nm value of the TMB colorimetric sample catalyzed by PMDs is significantly lower than that of the control sample (without streptomycin). Hence, the detection of streptomycin can be accomplished by detecting the change of OD 450nm (△OD 450nm ). Furthermore, when the concentration of the substrate TMB is lower, the catalytic activity of PMDs is inhibited more significantly by streptomycin. Under optimized conditions, this method has good detection specificity, could effectively distinguish streptomycin from other antibiotics (ampicillin, chloramphenicol, geneticin, and kanamycin), has a limit of quantitation (LOQ) of 5 mg/L, excellent linear performance, good repeatability, and a total detection time of less than 2 h, and can be employed for the detection of actual samples (laver and egg drop soup). This method circumvents the complex preparation process of experimental materials, is simple to operate, does not require fluorescent labeling, and is of low cost, providing a novel method for food safety supervision.