Home
This Title All WIREs
WIREs RSS Feed
How to cite this WIREs title:
WIREs Nanomed Nanobiotechnol
Impact Factor: 6.14

Magnetic quantum dots for multimodal imaging

Full article on Wiley Online Library:   HTML PDF

Can't access this content? Tell your librarian.

Abstract Multimodal contrast agents based on highly luminescent quantum dots (QDs) combined with magnetic nanoparticles (MNPs) or ions form an exciting class of new materials for bioimaging. With two functionalities integrated in a single nanoparticle, a sensitive contrast agent for two very powerful and highly complementary imaging techniques [fluorescence imaging and magnetic resonance imaging (MRI)] is obtained. In this review, the state of the art in this rapidly developing field is given. This is done by describing the developments for four different approaches to integrate the fluorescence and magnetic properties in a single nanoparticle. The first type of particles is created by the growth of heterostructures in which a QD is either overgrown with a layer of a magnetic material or linked to a (superpara, or ferro) MNP. The second approach involves doping of paramagnetic ions into QDs. A third option is to use silica or polymer nanoparticles as a matrix for the incorporation of both QDs and MNPs. Finally, it is possible to introduce chelating molecules with paramagnetic ions (e.g., Gd‐DTPA) into the coordination shell of the QDs. All different approaches have resulted in recent breakthroughs and the demonstration of the capability of bioimaging using both functionalities. In addition to giving an overview of the most exciting recent developments, the pros and cons of the four different classes of bimodal contrast agents are discussed, ending with an outlook on the future of this emerging new field Copyright © 2009 John Wiley & Sons, Inc. This article is categorized under: Diagnostic Tools > In Vivo Nanodiagnostics and Imaging

Schematic representation of the four types of magnetic quantum dots (QDs) that are discussed.

[ Normal View | Magnified View ]

(a) Two‐photon laser scanning microscopy image of a damaged murine carotid artery (ex vivo), showing high uptake of green‐emitting, annexin A5‐conjugated QDs with a Gd‐wedge coating in ECs and SMCs. EC, endothelial cells; SMC, smooth muscle cells; L, lumen; IEL, internal elastic lamina; EEL, external elastic lamina. Red: eosin, labeling elastin laminae; blue: syto41, labeling cell nuclei. (b) The same damaged artery shows a brighter contrast in an MR image (right) compared to an undamaged control artery (left). (a) and (b) are reprinted with permission from Ref. 65. Copyright (2007) American Chemical Society. (c) Design of a silica‐coated QD with negatively charged (THPMP), positively charged (APTS), and paramagnetic complexes (TSPETE) covalently bound to the silica surface. The dotted circles in the TSPETE complex represent the five coordination sites for Gd ions. Insert shows a TEM image of the particles. (Reprinted, with permission, from Ref. 66. Copyright 2006 Wiley‐VCH Verlag GmbH & Co. KGaA.).

[ Normal View | Magnified View ]

Multimodality imaging of tumor angiogenesis in mice. (a) Intravital microscopy of tumor blood vessels, (b) magnetic resonance imaging (MRI) of regions with high angiogenic activity in a subcutaneously growing tumor, and (c) fluorescence imaging of tumor angiogenesis feasible after intravenous administration of paramagnetic quantum dot (QD) micelles (as described in Ref. 19). Taken from Ref. 64.

[ Normal View | Magnified View ]

(a) Schematic drawing of a quantum dot (QD) (green) encapsulated in pegylated (red) and paramagnetic (yellow) lipids. A small fraction of the pegylated lipids was functionalized by an arginine‐glycine‐aspartic acid (RGD) peptide, which enables targeting to a cell surface receptor (green). (b) Fluorescence microscopy image of human umbilical vein endothelial cells (HUVEC) incubated with RGD‐conjugated paramagnetic QDs. (c) T1‐weighted magnetic resonance imaging (MRI) images of cell pellets incubated with RGD‐conjugated (upper right) or nonconjugated (bottom left) QDs, or not incubated at all (control). (Reprinted, with permission, from Ref. 19. Copyright 2006 American Chemical Society.).

[ Normal View | Magnified View ]

(a) Confocal microscope image of 5.6–µm polymer microcapsules containing red‐emitting CdTe quantum dots (QDs) and Fe3O4 MNPs, aligned by an external magnetic field. Reprinted with permission from Ref. 52. Copyright (2004) American Chemical Society. (b) TEM image of a ∼100 − nm copolymer nanosphere embedded with both CdSe/ZnS QDs and Fe2O3 MNPs. Reproduced with permission from Ref. 53. Copyright Wiley‐VCH Verlag GmbH & Co. KGaA. (c) Schematic representation of the synthesis of Fe3O4 MNPs encapsulated by both positively (PAH) and negatively (PSS) charged polyelectrolytes (PEs). After deposition of the PEs (steps 1–3), negatively charged QDs were attached (step 4). Multilayers of QDs could be embedded by repeating steps 1 to 4. (Reprinted, with permission, from Ref. 54. Copyright 2004 American Chemical Society.).

[ Normal View | Magnified View ]

Photographs of dispersions of various Fe2O3–CdSe heterodimer samples (as shown in Figure 2D). (A) shows that all particles are attracted by a magnet leaving behind a clear solution, and (B) illustrates the tunability of the emission color, by exciting two samples with a UV lamp (365 nm). (C) Confocal laser scanning microscopy of 4T1 mouse breast tumor cells incubated with oleyl‐PEG coated Fe2O3–CdSe heterodimers. (Reprinted, with permission, from Ref. 18 Copyright 2007 Wiley‐VCH Verlag GmbH & Co. KGaA.).

[ Normal View | Magnified View ]

(a) TEM image of composite silica particles with Fe2O3 MNPs and CdSe quantum dots (QDs) incorporated (right panel shows a magnified image), reprinted with permission from Ref. 40. Copyright (2005) American Chemical Society. (b) TEM image of multiple iron oxide MNPs incorporated in 170‐nm silica spheres. Enlarged image of the silica surface (insert) shows the presence of small CdTe QDs. Reproduced with permission from Ref. 45. Copyright Wiley‐VCH Verlag GmbH & Co.KGaA. (c) TEM image of CdSe/ZnS QDs (4.5 nm) and Fe3O4 MNPs (14 nm) both attached to the surface of 100‐nm silica particles. Insert shows a magnified image of the silica surface with a QD attached. (Reprinted, with permission, from Ref. 46. Copyright 2006 Wiley‐VCH Verlag GmbH & Co.KGaA.).

[ Normal View | Magnified View ]

(a) Synthetic route for generation of polymer‐coated, water‐soluble core/shell CdSe/Zn1–xMnxS quantum dots (QDs), and (b) their uptake by macrophages shown by confocal fluorescence microscopy (scale bar 20 µm). (c) T1‐weighted MRI on the lysates of cells that were incubated with the doped QDs (right) shows a stronger contrast compared to cells that were not incubated (left). (Reprinted, with permission, from Ref. 37. Copyright 2007 American Chemical Society.).

[ Normal View | Magnified View ]

(a) Magnetization curve for CdS:Mn/ZnS quantum dots (QDs). (b) Transmission and (c) fluorescence microscopy images of a cross‐section of the brain showing branches of the right middle cerebral artery after labeling with HIV‐1 TAT‐conjugated CdS:Mn/ZnS QDs. (Reprinted, with permission, from Ref. 36. Copyright 2005 American Chemical Society.).

[ Normal View | Magnified View ]

Transmission Electron Microscopy (TEM) images of (a) FePt/CdSe core/shell nanocrystals, reprinted with permission from Ref. 15. Copyright (2007) American Chemical Society. (b) FePt–CdS heterodimers, reprinted with permission from Ref. 16. Copyright (2004) American Chemical Society. (c) Cobalt/CdSe core/shell nanocrystals, reprinted with permission from Ref. 17. Copyright (2007) American Chemical Society. (d) HR‐TEM image of Fe2O3–CdSe heterodimers. The magnetic materials (FePt and Co) exhibit a stronger contrast in the TEM images than the semiconductor materials (CdSe and CdS). (Reprinted, with permission, from Ref. 18. Copyright 2007 Wiley‐VCH Verlag GmbH & Co. KGaA.).

[ Normal View | Magnified View ]

Related Articles

High‐resolution light microscopy using luminescent nanoparticles
Monodisperse magnetic nanoparticles for biodetection, imaging, and drug delivery: a versatile and evolving technology
Modeling breast biomechanics for multi‐modal image analysis—successes and challenges (WIREs Systems Biology and Medicine)
Magnetic resonance relaxation properties of superparamagnetic particles

Browse by Topic

Diagnostic Tools > In Vivo Nanodiagnostics and Imaging

Access to this WIREs title is by subscription only.

Recommend to Your
Librarian Now!

The latest WIREs articles in your inbox

Sign Up for Article Alerts