Light-emitting nanoparticles have been demonstrated to see deep into living tissue. The specially designed nanoparticles can be excited by ultra-low-power laser light at near-infrared wavelengths considered safe for the human body. They absorb this light and emit visible light that can be measured by standard imaging equipment.
The so-called alloyed upconverting nanoparticles (aUCNP) can be developed to attach to specific components of cells to serve in an advanced imaging system to light up even single cancer cells. Such a system could guide high-precision surgeries and radiation treatments and help to erase even very tiny traces of cancer. The laser power needed for the UCNPs is millions of times lower than the power needed for conventional near-infrared-imaging probes.
There are numerous medical scanning techniques to locate cancers — from mammograms to MRIs and PET-CT scans — but these can lack precise details at very small scales. It is important to know exactly where each cancer cell is hiding. An imaging sensor is being developed to integrate with nanoparticles that could be attached to surgical equipment or surgical gloves to pinpoint cancer hot spots during surgery.
For decades, the research community had believed that the best way to produce these upconverting materials was to implant them, or “dope” them, with a low concentration of metals known as lanthanides. Too many of these metals, researchers had believed, would cause the light they emit to become less bright with more of these added metals. Studies of individual UCNPs proved valuable in showing that erbium, a lanthanide previously thought to only play a role in light emission, can also directly absorb light and free up another lanthanide — ytterbium — to absorb more light.
The UCNPs used in the latest study measure about 12-15 nanometers (billionths of a meter) across — small enough to allow them to penetrate into tissue.