Broad-Range Magnetic Relaxation Switching Bioassays Using Click Chemistry-Mediated Assembly of Polystyrene Beads and Magnetic Nanoparticles.

Magnetic relaxation switching assays with a broad and tunable detection range can greatly improve current magnetic sensors for biochemical detections, but it remains challenging in terms of the limited detection range and low sensitivity. Herein, we report a methodology that uses click chemistry to assemble different sizes of polystyrene beads and magnetic nanoparticles to prepare versatile magnetic probes for broad-range bioassays with high sensitivity. Small magnetic nanoparticles can be controllably assembled on different sizes of polystyrene beads to form core-satellite structures, acting as broad-range probes that enable the magnetic relaxation switching assays with high sensitivity because different sizes of polystyrene beads can conjugate different numbers of small magnetic nanoparticles. On the basis of click chemistry, we assemble polystyrene beads and magnetic nanoparticles to develop a biosensing technique for analyzing three different antibiotics, with a high sensitivity and a tunable detection range from pg/mL to μg/mL.