Electrochemical sensor for detecting streptomycin in milk based on label-free aptamer chain and magnetic adsorption

•Magnetic mesoporous carbon was loaded on the magnetic electrode to prepare a sensor.•The selectivity of aptamer-streptomycin controls the electrical signal of reaction.•Molecule modelling reveals that aptamer-streptomycin has the highest affinity.•The sensor exhibits the detection limit of 0.015 nM for streptomycin detection. Exploiting a simple and sensitive sensor to efficiently detect streptomycin (STR) in milk is critical for resolving the harm caused to humans by STR residues. This study reports an electrochemical sensor using magnetic mesoporous carbon materials (MMCM) as a loaded material through magnetic adsorption immobilized on magnetic glassy carbon electrode (MGCE) and adsorbing unlabeled streptomycin aptamer (STP) as the identification element. The sensor can detect STR sensitively with a wide detection range (0.172–17.2 × 103 and 17.2 × 103 –17.2 × 105 nM) and a low detection limit of 0.015 nM. Experimental results revealed that the specific binding of STP with STR on the electrode changed the configuration of STP, thereby causing current change of differential pulse voltammetry curve. Compared with HPLC, this study provides a new method for rapid and sensitive detection of STR in milk (n = 5, 95 % confidence level, RSD＜5%).