Quantum Dot Tags

As we've already discussed, the fluorescent properties of certain quantum dots make them attractive candidates for a variety of targeted tagging for medical imaging.

Certain classes of quantum dots, mainly those based on Cadmium Selenide, exhibit size-dependent photoluminescence.  Larger quantum dots emit red light, while smaller dots will shift slowly towards blue light.  Our ability to create specific diameters of quantum dot is fairly good right now.  It is currently possible to make a wide variety of quantum dots that emit light in different frequencies.

The biggest challenge comes in finding a way for the dots to target specific molecules in the body.  Some researchers are trying to fictionalize the surface of the dots directly so they will bind to a specific molecule.  Unfortunately, quantum dots don't do very well in a solution by themselves.  Some form of stabilization is necessary.

That's where a variety of carriers have come into play.  One candidate for a carrier for quantum dots is the buckyball.  Buckyballs are extremely stable and have many functional sites for molecular attachment. 

Another research group, based at the University of Indiana in Bloomington, has successfully created a latex microbead that can be embedded with a variety of dots at the same time.  Such a composite could act like a barcode with a unique mixture of colors.  Latex beads can be fictionalized easily as well.

By combining both colors and intensities, researchers estimate that they could create some 10 million unique combinations for medical tagging.

The advantage of using quantum dots in medical imaging is obvious.  Current fluorescent dyes are not as bright, and they tend to diffuse quickly within the body.  Quantum dots, on the other hand, will quickly bind to a target and stay there, allowing for quick medical scans to be done.

Quantum dots have already found their way into some medical imaging techniques.  Though the technology is not yet perfected, it's already proven extremely useful as a super-bright tagging source.