A novel colorimetric aptasensor using cysteamine-stabilized gold nanoparticles as probe for rapid and specific detection of tetracycline in raw milk

In this paper, a sensitive and specific calorimetric aptasensor for rapid detection of tetracycline (TET) in raw milk was developed by using cysteamine-stabilized gold nanoparticles (CS-AuNPs) as the probe. The highly specific single-stranded DNA (ssDNA) aptamers which bind to TET with high affinity were employed to discriminate other antibiotics, such as oxytetracycline, doxycycline, ciprofloxacin, kanamycin, lomefloxacin, chloramphenicol, ofloxacin, enoxacin. The sensing approach is based on the strongly specific interactions between the TET-binding aptamers and TET over the electrostatic interactions between the negatively-charged TET-binding aptamers and the positively-charged CS-AuNPs. Thus a simple calorimetric aptasensor for TET determination is developed using CS-AuNPs as the calorimetric probe. Under the optimum conditions, the absorbance change (Delta A(527)) of CS-AuNPs was linearly proportional with TET concentration in the range of 0.20-2.0 mu g/mL with the detection limit of 0.039 mu g/mL (3 sigma), which is lower than the permissible level in the European Union (EU) (225 nM) and China (100 mu g/kg). The application of this method for samples of TET-spiked raw milk suggested satisfactory recoveries between 91.28% and 100.87%. Owing to the advantages of simple operation procedure, reduced detection time, and excellent selectivity, practical application of the proposed calorimetric assay could be expected to realize in on-site and real-time detection of TET in raw milk. (C) 2015 Elsevier Ltd. All rights reserved.