Editorial [Hot Topic: MR Contrast Agents for Molecular and Cellular Imaging (Guest Editor: Jeff W.M. Bulte)]

Molecular and cellular imaging is a relatively young field that is rapidly changing our approach towards understanding and solving problems in biology and medicine. Among the different imaging modalities, MR imaging offers both whole body penetration and high spatial and temporal resolution. Now that the hardware necessary to perform MR imaging in sufficient detail can be found in many places across the world, it is anticipated that future advances in molecular and cellular imaging will heavily depend on further development of MR probes and contrast agents. With this in mind, this special issue of Current Pharmaceutical Biotechnology offers a sampling of the current state-of-the-art of MR contrast agents that can be used to tag molecules and cells, as well as probe the biochemical microenvironment. The article by Artemov et al. describes different strategies that can be followed to target contrast agents to cell surface receptors. Lanza et al. report on the use of paramagnetic nanoparticles that can be derivatized for specific molecular imaging as well as drug delivery. Next is the review by Aime et al. on intracellular magnetic labeling using paramagnetic chelates and different uptake mechanisms. Lowe then follows and outlines the current status of so-called smart or activated contrast agents that can respond to changes in the microenvironment. Koretsky reviews the new emerging application of manganese to trace neuronal connextions in the brain. Kobayashi et al. are using dendrimers as macromolecular contrast agents and describe their various applications in MR imaging. Ho et al. employ superparamagnetic iron oxides to label macrophages in vivo for detection of these cells in various models of transplanted organ rejection. Finally, a contribution from our own Institute on the use of magnetic nanoparticles to monitor (stem) cell therapy closes this issue. I hope you will enjoy this issue as much as I did editing it.