Selected ssDNA aptamers-graphene oxide based fluorescent biosensor to detect sulfameter in milk.

Abstract

The abuse of sulfameter (SME) in animal husbandry can cause drug resistance and toxic or allergic reactions in humans. Therefore, it is very important to establish a simple, inexpensive and efficient method for detecting SME in food. In this work, we propose a single fluorescent aptamer/graphene oxide (GO)-based biosensor to detect SME residues in milk. Aptamers that specifically bind to SME were screened by capture-SELEX using an ssDNA library immobilized on magnetic beads. The 68 active candidate aptamers were chemically synthesized for specificity and affinity characterization. Among the aptamers, the aptamer sulf-1 revealed the highest affinity (Kd =77±15 nM) to SME and was selected to construct a GO-based fluorescent biosensor for real milk sample detection. Under optimal conditions, the single fluorescent aptasensor had a wide linear range (R2 was 0.997) from 7 to 336 ng/mL and low detection limit of 3.35 ng/mL that was calculated with a 3 SD/slope. The single fluorescent method was also validated by SME-fortified milk samples, showing average recoveries ranging from 99.01% to 104.60% with a relative standard deviation below 3.88%. These results demonstrate that this novel aptamer sensor provides an opportunity for sensitive, convenient and accurate detection of SME residues in milk.