(An) enzyme labeled electrochemical biosensor based on competition between aptamer duplex and molecule

Abstract

Aptamer, in vitro selected functional oligonucleotides, has been applied various biosensors due to its inherent selectivity, affinity, and diverse advantages. Many biosensors based on aptamer used electrochemical biomarker to detect biomolecules and signal amplification. [1] Signal amplification is one of the most important strategies in lowering detection limit of biosensors. Enzyme labels have been widely used because they can generate many electroactive signal reporting molecules. [2] Here we report a signal amplified electrochemical aptasensor using competitive between aptamer-complementary DNA couple and aptamer-target biomolecule couple. The gold electrode was modified with self-assembled monolayers of aptamers. Continually the aptamers make DNA double helix with biotinylated complementary s. In the absent of target biomolecules, strepavidin-conjugated alkaline phosphatase(ALP) can bind to the biotin. But in the presence, the target biomolecules replace the complementary DNA sequence so that the strepavidin-conjugated ALP can’t bind. It needs that the binding affinity between aptamer and target biomolecule is much higher than that of aptamer-complementary DNA couple, and we can make this circumstance by reducing the number of complementary binding base pairs of double helix. The competition results in a decrease of the enzyme product which can be detectable by electrochemical methods.