DSN-assisted split aptamer strategy coupled with gold nanoparticle growth for colorimetric detection of estradiol

Estradiol (E2) is a vital hormone and recognized endocrine disruptor that necessitates sensitive monitoring at trace concentrations. While existing analytical methods provide high accuracy, their cost and operational complexity emphasize the need for simpler, yet sensitive alternatives. Here, we report a colorimetric assay for the sensitive detection of E2 by integrating duplex-specific nuclease (DSN) activity with split aptamer recognition and gold nanoparticle (AuNP) growth. In this design, E2 induces the hybridization of split aptamer fragments on AuNP surfaces, which are subsequently cleaved by DSN, leading to shortened surface DNA strands and altered nanoparticle passivation. This process induces heterogeneous gold growth upon gold (III) reduction, producing distinct colorimetric shifts that can be observed visually and quantified spectroscopically. Under optimized conditions, the assay exhibited a linear response in the range of 1-400 ng/mL with a detection limit of 1 ng/mL. This platform exhibited good selectivity against structurally related hormones and other potential interferents. Measurements in spiked human serum showed good agreement with commercial ELISA results, yielding a Pearson correlation coefficient of 0.91. This DSN-assisted split aptamer-AuNP strategy offers a straightforward and sensitive approach for detecting small molecules, with promising potential for clinical diagnostics.