Target-induced Strand Displacement-based Electrochemical Aptasensor for the Determination of Tobramycin in Milk by Differential Pulse Voltammetry (DPV)

A target-induced strand displacement (TISD) electrochemical aptasensor is reported for the sensitive determination of tobramycin (TOB). A novel substrate was synthesized by loading cerium-based metal organic framework (Ce-MOF) that was modified by Pd nanoparticles (PdNPs), onto polyethyleneimine (PEI)-modified molybdenum disulfide (MoS2). The substrate (denoted by PEI-MoS2/Ce-MOF@PdNPs) was used to modify the Au electrode (AuE) to expand the electrode surface area for subsequent cDNA loading. Gold-platinum core-shell particles (Au@Pt) loaded with aptamers (Apt) were introduced as signal tags and mimetic peroxidase to hybridize with cDNA and form a double-stranded structure. When the target was present, strand displacement dominated by TISD occurred and the signal tag was released from the electrode surface, turning the signal off. Using the optimal conditions, the linear range of the sensor was from 5 x 10(-11) to 1 x 10(-6 )mol/L and the detection limit was 1.05 x 10(-12 )mol/L with good stability, reproducibility, and specificity. The aptasensor provided good performance for the determination of tobramycin in milk.