Recent advances on magnetic nanobead based biosensors: From separation to detection

Magnetic nanobeads have been widely used for magnetic separation, target labeling and signal amplification in the development of various biosensors. This review summarized (1) the basic knowledge of magnetic nanobeads, including physical structure, chemical characteristics and surface modification; (2) the development and applications of magnetic separation, from the earliest conventional magnetic separation, to high gradient magnetic separation, then to magnetophoretic separation and magnetic continuous-flow separation, finally to the latest magnetic grid separation; and (3) recent advances and applications of magnetic nanobead based biosensors, where the magnetic nanobeads work as either detection signal for electromagnetic biosensors, magnetic lateral flow biosensors and magnetic relaxation switching biosensors, or signal amplifying tag for electrochemical biosensors, QCM biosensors and SPR biosensors, or both. Besides, the important issues and future trends for magnetic nanobead based separation and biosensor were also discussed and summarized.