Highly Sensitive Detection of Bisphenol A by NanoAptamer Assay with Truncated Aptamer

For the sensitive quantification of bisphenol A (BPA), we have developed NanoAptamer assay, which employs aptamer and complementary signaling DNA, a set of quantum dots (QD), and magnetic beads (MBs). Signaling DNA–QD₆₅₅ was tethered to MB–QD₅₆₅ via the aptamer. The affinity of the aptamer to BPA resulted in the release of the signaling DNA–QD₆₅₅ from the complex and hence the corresponding decrease in the QD₆₅₅ fluorescence measurement signal. Three new aptamers (23, 58, and 24-mer) were designed via truncation of the reference aptamer (73-mer). The sensitivity and selectivity of each aptamer for BPA detection via NanoAptamer assay were investigated. One of the truncated aptamers (24-mer) has shown a significantly better performance (limit of detection, LOD, 0.17 pg/mL) than the reference 73-mer aptamer (LOD, 570 pg/mL). It has also shown the best selectivity for BPA detection over BPA analogues (i.e., bisphenol B, bisphenol C, and diethylstilbestrol). It corresponded to a normalized fluorescence change of 33.7% at the environmentally relevant concentration of 1 ng/mL (1 ppb) BPA; however, the analogues remained unchanged (2.3–3.9%)