In this review, we introduce various magnetic biosensors that have been developed. We first explain the advantages of magnetic biosensing and their general operating principles as well as the biolabeling technique for magnetic nanoparticles. Next, we focus on magnetoresistive biosensing technologies because magnetoresistive biosensors will be an essential development direction due to the demand for miniaturization and portable lab-on-a-chip devices. The magnetoresistive effects employed in biosensing include anisotropic magnetoresistance, giant magnetoresistance and tunneling magnetoresistance. In addition to magnetoresistive sensors, the advantages and disadvantages of some nonmagnetoresistive magnetic biosensors are discussed and compared. Finally, we introduce research on integrating magnetic biosensors into the microfluidic laboratory-on-a-chip systems and comment on future development trends.

Tc complexes with kethoxal bis(thiosemicarbazone) ligands have been prepared, aimed to develop as a hypoxia imaging agent. The ligands have been synthesized by the combination of kethoxal and thiosemicarbazide as shown below: 99m oc 2H5 CHO kethoxal thiosern icarbazide , C H 3 R , = HC R 2=H R 3 = R 4=H, or C H 3 'OC 2H5One of the precursors, kethoxal, which is not commercially available, can be prepared by the SeOz oxidation of crotonaldehyde in C2H50H as shown below: