| Summary: | Impedimetric aptasensors without signal amplification exhibit poor sensitivity for the detection of small molecule contaminants. In this work, biotinylated nanoparticles of biotin-FNPs were readily prepared by the self-assembly of biotin-phenylalanine (biotin-Phe) monomers. The biotin-FNPs were then used for the development of competitive impedimetric aptasensors by streptavidin–biotin (SA–biotin) coupling chemistry. Specifically, capture of biotinylated DNA (biotin-DNA) by the aptamer-modified electrode allowed for the in situ formation of SA–biotin-FNPs networks on the electrode surface, hampering the electron transfer by creating an insulating layer. The target–aptamer interaction prevented the capture of biotin-DNA, thus inhibiting the formation of SA–biotin-FNPs networks on the electrode surface and allowing for the electron transfer. To demonstrate the analytical performances of the strategy, aflatoxin B1 (AFB1) was determined as the model analyte. The aptasensor exhibited a linear range of 0.05–3 pg/mL. The detectable concentration is much lower than that achieved by other impedimetric aptasensors. The strategy may provide a general way for the design of biosensors to determine various small molecules by matching sequence-specific aptamers.
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