Competitive impedimetric aptasensors for detection of small molecule pollutants by the signal amplification of self-assembled biotin-phenylalanine nanoparticle networks

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 B-1 (AFB(1)) 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.