For the past two decades, researchers have been manipulating tiny clumps of atoms to exploit their quantum mechanical properties in computing, optics, and electronics. Now Moungi G. Bawendi envisions uses for these quantum dots as alternatives to fluorescent organic dyes and proteins for labeling, imaging, and monitoring biological systems and for better understanding and battling cancer.
Also called artificial atoms, quantum dots are nanometer-scale “boxes” containing a few hundred to a few thousand atoms that selectively hold or release electrons. Depending on their size, quantum dots can be “tuned” to emit any color in the rainbow, with the added bonus that the light they produce is much more saturated than that of other sources.
Quantum dots can be engineered to interact with biological tissue and to report back on what they encounter. Bawendi, Lester Wolfe Professor in Chemistry, measures the dynamics of these tiny semiconductor particles as they interact with cells and tissues at the level of individual molecules. Working with researchers at Massachusetts General Hospital, Beth Israel Deaconess Medical Center and chemists at MIT, Bawendi is injecting these dots into laboratory animals to shed light on the microbiology of tumors.
“We’re making dots that are smarter. They report not only where they are in the tumor to help image the tumor spatially and chemically, but also report on the microbiology within the cells,” Bawendi said. This gives researchers a read on what is going on at cancer’s ground zero, illuminating the effects of chemotherapy and how to tweak the timing of a dose for maximum effect.
Bawendi is using quantum dots to tag and image single stem cells, and to fluoresce in different colors when exposed to different biological substances, indicating certain concentrations of oxygen and glucose and acidity. Quantum dots can provide a pathway for a potential workaround to drug particles too big to permeate a cell wall: they can serve to help design nanoparticle systems that transport a payload to the outside of a tumor and then fall apart in the presence of enzymes, depositing the drugs where they can diffuse into the tumor. Researchers also are experimenting with quantum dots shaped like rods and spheres to see which are best at permeating tissues and cell walls.
Bawendi finds tumors formidable foes. “They’re complicated on so many fronts,” he said. “Every tumor is different. Biologically and morphologically, they are incredibly complicated, so any tool we can use to uncover their microbiology and promote the delivery of existing therapeutics may prove invaluable. This is an area where quantum dots can contribute something significant.”