High sensitive rapid visual detection of sulfadimethoxine by label-free aptasensor.

Quickly and sensitively detection of antibiotic residues in animal products often requires time-consuming techniques and expensive instrumentation. To address these limitations, a high sensitive aptasensor for sulfadimethoxine (SDM) using unmodified gold nanoparticles (AuNPs) was developed in the present study. The assay sensitivity was improved by optimizing several key parameters such as the amount of aptamer adsorbed to AuNPs, the concentration of salt and the AuNPs pH value. To our knowledge, this is the first time to investigate the effect of AuNPs pH value on the sensitivity of aptamer-AuNPs based label-free assay. The best procedure for SDM analysis in our system was: the pH value at 8.0, and the concentration of aptamer at 2 μM, and the concentration of salt at 2 M. The linear range for the current analytical system was from 50 ng/mL to 1 μg/mL, and the detection limit was 50 ng/mL, which is lower than the Maximum Residue Limit (MRL) (100 ng/mL) in edible animal tissues regulated by China and European commission. Our study provides a simple, fast, and easy to read method for SDM analysis with high sensitivity, which can be applied in future on-site detection in animal products.