All-Solid-State Potentiometric Aptasensing of Streptomycin Based on Signal Amplification by Polycation

An all-solid-state potentiometric aptasensor based on signal amplification by polycation has been proposed for the detection of streptomycin. The carboxylated multi-walled carbon nanotubes (CMWCNTs), polyethylenimine (PEI), and the aptamers of streptomycin were assembled successively on the screen-printing carbon electrode surface by Layer-by-Layer (LbL) technique. The streptomycin would specifically bind to the aptamers, leading to the release of aptamers from the modified electrode surface. Thus, the charges of electrode were changed, causing the variation of open circuit potential (OCP). The introduction of polycation - PEI makes the electrode exposing a large amount of positive charges, so it can combine more aptamers to realize signal amplification. Consequently, under the optimal conditions, this aptasensor showed high sensitivity with corresponding linear response ranges of 1.00 χ 10_11 _ 1.00 χ 10_9 M, and a detection limit of 3.43 χ 10_12 M. Moreover, this aptasensor presented good selectivity, reproducibilityand stability. It could be applied to the detection of milk samples, demonstrating the practicability of this aptasensor.