Quantum dots could expand live imaging

When it comes to imaging live tissue, short-wavelength infrared (SWIR) radiation penetrates farther and scatters less than more-traditional near-IR and visible light. But a lack of agents that fluoresce brightly in the SWIR region (about 1,000 to 2,000 nm) has impeded the development of this type of imaging in the body. Moungi G. Bawendi, Oliver T. Bruns, and Thomas S. Bischof of MIT and coworkers have now created quantum dots that could expand SWIR live imaging (Nat. Biomed. Eng. 2017, DOI: 10.1038/s41551-017-0056). They coated InAs cores with CdSe, CdS, CdSe-ZnSe, or CdS-ZnSe single or double layers and derivatized the resulting quantum dots with organic functional groups to customize them—for instance, to have long blood circulation times. The quantum dots emit SWIR radiation about an order of magnitude more strongly, are more stable, and have narrower and more tunable emission spectra than previous SWIR probes. In live imaging, the quantum dots also allow faster acquisition speeds and higher sensitivity than previous SWIR emitters. In live mice and in real time, the researchers used the emitters to measure metabolic turnover rates in several organs simultaneously, to quantify heartbeat and breathing rates, and to map brain vasculature. The quantum dots have constituents such as cadmium that aren’t necessarily suitable for human use, but the researchers hope to eventually make versions of the particles that are safe for use in the clinic.