An ultrasensitive HRP labeled competitive aptasensor for oxytetracycline detection based on grapheme oxide-polyaniline composites as the signal amplifiers

In this work, we explored an amplification strategy which was based on graphene oxide-polyaniline (GO-PANI) and horseradish peroxidase (HRP) to construct the competitive aptasensor for ultrasensitive detection of oxytetracycline (OTC). In the protocol, the GO-PANI film was immobilized on the surface of the electrodes. Then, gold nanoparticles (AuNPs) were electrodeposited on the electrode surface using a constant potential stripping technique. The selected aptamer which had high affinity and specificity for OTC was used as a capture probe and labeled with HRP. The linear response to OTC concentration of the developed aptasensor was in the range of 4.0 x 10(-6) mg L-1 to 1.0 mg L-1. The detection limit (LOD) of 2.3 x 10(-6) mg L-1 was obtained (S/N = 3). In addition to good repeatability and stability, the proposed aptamer sensor also showed the advantages of low background current and high sensitivity to examine OTC in real samples.