Magnetically engineered semiconductor quantum dots as multimodal imaging probes.

Light-emitting semiconductor quantum dots (QDs) combined with magnetic resonance imaging contrast agents within a single nanoparticle platform are considered to perform as multimodal imaging probes in biomedical research and related clinical applications. The principles of their rational design are outlined and contemporary synthetic strategies are reviewed (heterocrystalline growth; co-encapsulation or assembly of preformed QDs and magnetic nanoparticles; conjugation of magnetic chelates onto QDs; and doping of QDs with transition metal ions), identifying the strengths and weaknesses of different approaches. Some of the opportunities and benefits that arise through in vivo imaging using these dual-mode probes are highlighted where tumor location and delineation is demonstrated in both MRI and fluorescence modality. Work on the toxicological assessments of QD/magnetic nanoparticles is also reviewed, along with progress in reducing their toxicological side effects for eventual clinical use. The review concludes with an outlook for future biomedical imaging and the identification of key challenges in reaching clinical applications.