At Biopolis, a sprawling research complex in Singapore, Chi Ching Goh leans over an anaesthetized mouse lying on the table in front of her, and carefully injects it with a bright yellow solution. She then gently positions the mouse's ear underneath a microscope, and flips a switch to bathe the ear in ultraviolet light. Seen through the microscope's eyepiece, the illumination makes the blood underneath the skin glow green, tracing the delicate vessels that carry the solution through the creature's body.
Ultimately, Goh, a PhD candidate at the National University of Singapore, hopes that the method will help her to find blood vessels that are leaking owing to inflammation, perhaps helping to detect malaria or predict strokes. Crucial to her technique are the virus-sized particles that give the solution its colour. Just a few tens of nanometres across, they are among a growing array of 'nanolights' that researchers are tailoring to specific types of fluorescence: the ability to absorb light at one wavelength and re-emit it at another.
Many naturally occurring compounds can do this, from jellyfish proteins to some rare-earth compounds. But nanolights tend to be much more stable, versatile and easier to prepare — which makes them attractive for users in both industry and academia.
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