Coated Ultrasmall Quantum Dots Suitable for In Vivo Imaging

Dec 03, 2007

Quantum dots have shown promise in a variety of imaging and therapeutic applications, particularly when they are coated to render them biocompatible. However, such coating can increase the size of quantum dots signficantly, which can adversely effect their pharmacokinetic and biodistribution properties.

Now, researchers at the Massachussetts Institute of Technology and Beth Israel Deaconess Medical Center have developed a new procedure that produces ultracompact quantum dots. Tests with these new materials show that this coating not only does not impair the superior optical properties of the quantum dots but also improves how the quantum dots behave in living animals.

Moungi Bawendi, Ph.D., a member of the MIT-Harvard Center of Cancer Nanotechnology Excellence, and John Frangioni, M.D., Ph.D., led this study. Their results appear in the Journal of the American Chemical Society.

To create these compact quantum dots, the investigators first create dual-layer nanocrystals that have a zinc-cadmium-sulfide (ZnCdS) core surrounded by a cadmium selenide (CdSe) shell. This combination of materials creates a compact yet bright quantum dot. Next, the researchers add a coating of cysteine, a sulfur-containing amino acid that binds tightly to the CdSe shell.

When stored in the presence of a reducing agent, these quantum dots are stable for 1 week at room temperature and at least 3 months at 4°C. Dynamic light scattering, a technique used to study nanoparticle size, showed that the diameter of these quantum dots was 5.9 nanometers. More importantly, their size did not increase when incubated with serum, demonstrating that the cysteine coating prevented proteins from collecting on the quantum dot surface.

The researchers note that the exceptionally small size of their quantum dots and their stability in serum led to new in vivo behavior. When injected into rats, the majority of the quantum dots accumulated in the bladder within 4 hours, demonstrating that these nanoparticles are small enough to be filtered out of the kidneys. In practical terms, this finding suggests that these compact quantum dots, if attached to a small targeting molecule, could be used to image tumors without having to worry about accumulation within the body. Any injected dose that did not bind to its target would clear rapidly, decreasing background noise and improving the sensitivity of tumor imaging.

This work, which was supported in part by the National Cancer Institute’s Alliance for Nanotechnology in Cancer, is detailed in the paper "Compact cysteine-coated CdSe(ZnCdS) quantum dots for in vivo applications." This paper was published online in advance of print publication. An abstract of this paper is available through PubMed.

Source: National Cancer Institute

Explore further: New electronic stent could provide feedback and therapy—then dissolve

Related Stories

Putting a new spin on plasmonics

May 07, 2015

Researchers at Finland's Aalto University have discovered a novel way of combining plasmonic and magneto-optical effects. They experimentally demonstrated that patterning of magnetic materials into arrays ...

Many uses in researching quantum dots

May 04, 2015

It's easier to dissolve a sugar cube in a glass of water by crushing the cube first, because the numerous tiny particles cover more surface area in the water than the cube itself. In a way, the same principle applies to the ...

Quantum dot TVs are unveiled at China tech expo

Apr 18, 2015

At this month's China Information Technology Expo (CITE) event, a headline-maker was the launch of quantum dot televisions, by QD Vision and Konka, the consumer electronics company. QD Vision's calling card ...

Researchers fine-tune quantum dots from coal

Mar 18, 2015

Graphene quantum dots made from coal, introduced in 2013 by the Rice University lab of chemist James Tour, can be engineered for specific semiconducting properties in either of two single-step processes.

Recommended for you

Non-aqueous solvent supports DNA nanotechnology

19 hours ago

Scientists around the world are using the programmability of DNA to assemble complex nanometer-scale structures. Until now, however, production of these artificial structures has been limited to water-based ...

Nanosilver and the future of antibiotics

20 hours ago

Precious metals like silver and gold have biomedical properties that have been used for centuries, but how do these materials effectively combat the likes of cancer and bacteria without contaminating the ...

User comments : 0

Please sign in to add a comment. Registration is free, and takes less than a minute. Read more

Click here to reset your password.
Sign in to get notified via email when new comments are made.