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

BACKGROUND A simple and rapid detection method for 17β‐estradiol (E 2 ) in complex food matrix is greatly desirable. A magnetic relaxation switch (MRS) sensor for detecting E 2 based on the aptamer‐functionalized gold‐coated iron oxide (Fe 3 O 4 @Au) nanocomposite was designed in this study. Fe 3 O 4 @Au nanoparticles (NPs) played as a ‘switch’ between dispersed and aggregated states, while aptamer served as the recognition unit. RESULTS According to the sensing effect of monocomponent relaxation time ( T 2W ) for E 2 , the volume ratio of aptamers to Fe 3 O 4 @Au, the sodium chloride (NaCl) concentration, the concentration of Fe 3 O 4 @Au@Apt, and reaction time were optimized to be 4:1, 0.03 mol L –1 , 4 μmol L –1 and 15 min, respectively. For the analysis of food sample, the E 2 was quantified over a concentration range of 1 to 100 nmol L –1 with a detection limit of 7.6 nmol L –1 for milk samples, while a linearity range of 20 to 100 nmol L –1 and a detection limit of 8.57 nmol L –1 for egg samples. CONCLUSION These results exhibited that the MRS sensor could be a promising platform for the rapid detecting of E 2 in food sample. © 2021 Society of Chemical Industry.