Aptamer-Based Fluorescent Switch for Sensitive Detection of Oxytetracycline

Abstract

Oxytetracycline (OTC) is one of the most used antibiotics in veterinary medicine. There is a large concern about developing antibiotic resistance in humans as a result of the consumption of products contaminated with OTC, so a fast detection technique for an on-field screening test is highly in demand. Here we introduce a novel aptasensor for fast detection of OTC, based on a triple helix molecular switch (THMS) complex formation. The limit of detection (LOD) of this sensor was 1.67 and 6.44 nM in phosphate buffer and milk samples, respectively. Moreover, the sensor showed a high selectivity towards OTC.

Aptamer Sensors for the Detection of Antibiotic Residues— A Mini-Review

“…Thus, it is necessary to introduce fluorescent groups/molecules, fluorescent nanomaterials, and quantum dots to construct a fluorescence-based aptamer-sensing system. An aptamer fluorescent sensing system can be roughly divided into the following types: (1) Classical molecular beacon fluorescence sensing system by aptamer labeling of fluorescence/quencher groups [ 103 , 104 , 105 ] ( Figure 4 a): there are two added arm segments and the loop sequence of the signal transduction probe (STP), with an open configuration for the STP probe, where the fluorophore is far from the quencher and thus can give rise to a fluorescence event, and after binding of OTC to the aptamer, the STP is released, forming a stem loop structure that quenches the fluorescence. (2) Fluorescence-quenched sensing system of aptamers (or complementary chains) labeled with fluorescent groups and carbon nanomaterials (graphene/carbon nanotubes) [ 106 , 107 , 108 ] ( Figure 4 b): the FAM-modified aptamer can be adsorbed onto the rGO surface via π-π interactions, which induce them into fluorescence resonance energy transfer (FRET) proximity, leading to fluorescence quenching by rGO, while the formation of an OTC–aptamer complex decreases the exposure of nucleobases, which makes the dyes detach from the rGO surface, thus producing a restoration of fluorescence.…”

“…The system’s fluorescence signal decreases, and tetracycline can be detected with a detection limit of 2.09 × 10 −9 mol/L. A fluorescence detection method for oxytetracycline was also constructed, with a detection limit of 1.67 × 10 −9 mol/L [ 103 ].…”

“… Sensing principle for the aptamer-based fluorescent sensor. ( a ) Target sensing based on aptamer molecular beacon labeled with fluorescence/quencher [ 103 ]. ( b ) Target sensing based on the fluorescence quenching by carbon nanomaterials [ 108 ].…”