A magnetic relaxation switch sensor for determination of 17β-estradiol in milk and eggs based on aptamer-functionalized Fe 3 O 4 @Au nanoparticles

A simple and rapid detection method for 17β-estradiol (E ) in complex food matrix is greatly desirable. A magnetic relaxation switch (MRS) sensor for detecting E based on the aptamer-functionalized gold-coated iron oxide (Fe O @Au) nanocomposite was designed in this study. Fe O @Au nanoparticles (NPs) played as a 'switch' between dispersed and aggregated states, while aptamer served as the recognition unit. According to the sensing effect of monocomponent relaxation time (T ) for E , the volume ratio of aptamers to Fe O @Au, the sodium chloride (NaCl) concentration, the concentration of Fe O @Au@Apt, and reaction time were optimized to be 4:1, 0.03 mol L , 4 μmol L and 15 min, respectively. For the analysis of food sample, the E was quantified over a concentration range of 1 to 100 nmol L with a detection limit of 7.6 nmol L for milk samples, while a linearity range of 20 to 100 nmol L and a detection limit of 8.57 nmol L for egg samples. These results exhibited that the MRS sensor could be a promising platform for the rapid detecting of E in food sample. © 2021 Society of Chemical Industry.