
422 Biosensors Based on Nanomaterials and Nanodevices
superparamagnetic NPs can attract each other when placed in external magnetic eld
gradient while they could form stable colloids in the absence of the eld. The large sur-
face area of the magnetic NPs provides an excellent platform to interact with molecules
in solution. After the reaction on the surface, the magnetic NPs can be separated expos-
ing them to magnetic eld gradients. Tagging the magnetic NPs is possible via chemical
modication of the surface of the magnetic NPs. There are a number of specic magnetic
separation techniques used depending on the purpose of the magnetic separation. ...