Rapid and sensitive detection of Bisphenol A in water by LF-NMR based on magnetic relaxation switch sensor

Abstract

A sensitive and rapid method for Bisphenol A (BPA) detection in water is always in high demand. A novel and accurate aptamer-functionalized magnetic relaxation switch (MRS) sensor was developed for the detection of BPA, which is based on the transverse relaxation time (T2) change of water protons that originated from the dispersion/aggregation of magnetic nanoparticles (MNPs). Aptamer-functionalized MRS sensor was prepared and characterized. Based on the linear relationship between BPA concentration and the magnetic relaxation characteristic signal (including the T2 attenuation curve, T2W, and T2 distribution), the mono-exponential fitting of Carr-Purcell-Meiboom-Gill (CPMG) decay (T2W) was finally chosen as the magnetic relaxation characteristic detection signal. According to the sensing effect of the aptamer-functionalized MRS sensor for BPA, the concentration of Fe3O4@SiO2 ~ Apt NPs, incubation times, and pH of the detection system were optimized to be 0.005 mg/mL, 15 min and 7, respectively. In the quantitative analysis of BPA, the detection working range was between 10 ng/mL and 100 ng/mL, and the limit of detection (LOD) was determined to be 2.9 ng/mL, which satisfied the safety limit set by China (10 ng/mL) and the European Union (0.6 mg/kg). Besides, the average recoveries of BPA in spiked water samples ranged from 92.6% to 103.1%, the intra-day and inter-day results all showed good precision (RSD values less than 15%). The results indicated that the proposed sensor could be a useful tool for sensitive and accurate analysis of BPA in water.