A simple FRET-based turn-on fluorescent aptasensor for 17 beta-estradiol determination in environmental water, urine and milk samples

A competitive fluorescent aptasensor was constructed based on fluorescence resonance energy transfer (FRET) for determination of 17 beta-estradiol (E2). Initially, carboxyfluorescein (FAM)-labeled E2 aptamer and its partially complementary DNA modified with Black Hole Quencher 1 (BHQ1) formed aptamer/DNA duplexes and triggered fluorescence quenching. When E2 was added to compete for aptamer-binding sites with cDNA, FAM fluorescence was recovered as a result of cDNA release from the aptamer/DNA duplexes. With a competitive turn-on aptasensor, E2 could be quantitatively detected by monitoring fluorescence enhancement. Under optimized conditions, this assay exhibited a linear response to E2 within the range from 0.1 ng.mL(-1) to 10 mu g.mL(-1), with the detection limit of 0.1 ng.mL(-1) (0.35 nM). This assay has been successfully applied to determination of E2 in environmental, biological and food samples with low cost and simple pretreatment process, requiring no complicated operations. The results showed high selectivity and good recovery. The present strategy holds great potential in detection of E2 in complex matrixes and becomes important in environmental monitoring, food safety and human health.