Target-induced recycling assembly of split aptamer fragments by DNA toehold-mediated displacement for the amplified colorimetric detection of estradiol

Estradiol is an endogenous hormone that affects many physiological functions in humans; thus, the demand for its detection has been increasing. Gold nanoparticle (AuNP)-based colorimetric sensors with split aptamers offer an easy-to-operate detection method for estradiol. However, the assay performance is still unmet. Here, we report a simple and sensitive colorimetric assay for the detection of estradiol, based on the target-induced recycling assembly of split aptamer fragments. This method contains three DNA fragments that remain in a metastable state without a target. After adding estradiol, the split aptamers assemble with the target, which can be regenerated by helper DNA, resulting in the formation of a three-way junction (3WJ)-like structure and the recycling of recognition. The generation of the 3WJ-like DNA structure causes the formation of unstable AuNPs, enhancing the salt-induced aggregation of AuNPs. The assay shows a detection limit of 0.7 nM, which is better than those of other aptamer-based detection methods. Moreover, the assay enables the detection of estradiol spiked in urine by avoiding any interference from contaminants. The colorimetric assay includes anti-estradiol DNA split aptamers, accounting for no false responses to non-target molecules. Therefore, the results demonstrated that it has application potential for the detection of estradiol in a complex matrix.