Lateral flow aptasensor for progesterone: Competitive target recognition and displacement of short complementary sequences

There is a pressing need for simple and accurate analytical tools to assess the level of EDCs in environmental samples. In this work, a simple and highly sensitive competitive lateral flow assay (LFA) was developed for progesterone (P4). Gold nanoparticles (AuNPs) were functionalized with a previously isolated 60-mer aptamer for P4 and further hybridized with 8-mer complementary sequence modified with biotin. In the absence of P4, AuNP-duplexed aptamer conjugates are capture by a test line made with streptavidin. Conformational change within aptamer sequence upon target recognition causes the release of the biotinylated complementary sequence and disappearance of the colored test line. By optimizing the hybridization location of the 8-mer biotinylated sequences, the sensitivity of sensor was improved by 20-folds to achieve 5 nM detection level of P4 in buffer and spiked tap water samples. The simply fabricated sensor demonstrated a dynamic range in the lower nanomolar range and excellent selectivity against potential interfering molecules including the closely similar 17 beta-estradiol (E2). The sensor can be used as a fast screening tool to assess the level of P4 in water. Implementing the developed assay avoids applying laborious extraction procedures and lengthily analysis by conventional chromatography based instruments.