Facile and rapid magnetic relaxation switch immunosensor for endocrine-disrupting chemicals

In order to develop facile, fast and sensitive detection methods for endocrine-disrupting chemicals (EDCs), we described a sensitive biosensing system involving magnetic relaxation switch, based on the assembly of cross-linked superparamagnetic iron oxide (CLIO) nanoparticles induced by the antigen–antibody biorecognition. The design of smart CLIO-based superparamagnetic iron oxide nanoparticles and antigen-OVA was described for the detection of bisphenol A [2,2-bis (4-hydroxyphenol) propane (BPA)]. The addition of BPA to the rapid magnetic relaxation switch immunosensor led to transverse relaxation time (T2) shortening compared to a blank control as shown by NMR relaxometry measurements. This process was also applied to the rapid and facile determination of concentrations of BPA in drinking water (tap water). Good linearity for all calibration curves was obtained, and the limit of detection (LOD) for BPA was 0.4 ng/mL in tap water.

► Antigen-OVA functionalized superparamagnetic iron oxide nanoparticles were synthesized.
► The magnetic relaxation switch immunosensor was successfully developed and applied to determination of EDCs in drinking water.
► The detection protocol is a one-step process, with an operation time of less than 1 h at room temperature, and the sensitivity is as low as 0.4 ng/mL.