Screening of a broad-spectrum aptamer and its application in the fabrication of an aptasensor for the detection of sulfonamides in animal-derived foods

Sulfonamides (SAs) are commonly used in livestock. However, excessive residues of these substances in animal-derived foods pose health risks to consumers. Therefore, there is an urgent need for simple, high-throughput techniques that can simultaneously detect multiple SAs or groups of SAs, enabling rapid assessment of total SA residues in animal-derived foods. In this study, a sulfadiazine (SDZ)-specific aptamer was successfully selected using a graphene oxide-based-Systematic evolution of ligands by exponential enrichment (SELEX). The aptamer was subsequently optimized and truncated to a 16-nucleotide sequence (SAs16-1: 5′-AGGGCTTCAACGGCAC-3′), which retained comparable binding affinities for SDZ, sulfadimethoxine (SDM), and sulfamethoxypyrimidine (SMP), with dissociation constants ranging from 74.12 to 116.16 nM. A novel Fe₃O₄/gold (Au)/graphitic carbon nitride (g-C₃N₄)-based fluorescent aptasensor, incorporating SAs16-1 for simultaneous detection of SDZ, SDM, and SMP, was further developed. Under optimized conditions, the linear detection ranges of SDZ, SDM, and SMP were 5-120, 3.25-150, and 10-110 ng/mL, respectively, with detection limits of 2.31, 1.94, and 5.86 ng/mL. Spiked recovery experiments in real food samples showed recovery rates of 85.16-111.52%, with a coefficient of variation below 15%. Furthermore, the aptasensor’s results were positively correlated with those obtained using high-performance liquid chromatography (HPLC). In conclusion, this novel aptasensor offers a rapid, cost-effective, and sensitive method for screening total residues of SDZ, SDM, and SMP in animal-derived foods, and holds great potential for widespread application in food safety testing.