Aptamer/Au nanoparticles/cobalt sulfide nanosheets biosensor for 17 beta-estradiol detection using a guanine-rich complementary DNA sequence for signal amplification

摘要

We have developed a sensitive sensing platform for 17 beta-estradiol by combining the aptamer probe and hybridization reaction. In this assay, 2-dimensional cobalt sulfide nanosheet (CoS) was synthesized by a simple hydrothermal method with L-cysteine as sulfur donor. An electrochemical aptamer biosensor was constructed by assembling a thiol group tagged 17 beta-estradiol aptamer on CoS and gold nanoparticles (AuNPs) modified electrode. Methylene blue was applied as a tracer and a guanine-rich complementary DNA sequence was designed to bind with the unbound 17 beta-estradiol aptamer for signal amplification. The binding of guanine-rich DNA to the aptamer was inhibited when the aptamer captured 17 beta-estradiol. Using guanine-rich DNA in the assay greatly amplified the redox signal of methylene blue bound to the detection probe. The CoS/AuNPs film formed on the biosensor surface appeared to be a good conductor for accelerating the electron transfer. The method demonstrated a high sensitivity of detection with the dynamic concentration range spanning from 1.0 x 10(-9) to 1.0 x 10(-12) M and a detection limit of 7.0 x 10(-13) M. Besides, the fabricated biosensor exhibited good selectivity toward 17 beta-estradiol even when interferents were presented at 100-fold concentrations. Our attempt will extend the application of the CoS nanosheet and this signal amplification assay to biosensing areas. (C) 2014 Elsevier B.V. All rights reserved.