Quantum clearance
The paper:
H.S. Choi et al., "Renal clearance of quantum dots," Nat Biotech, 25:1165–70. (Cited in 74 papers)
The finding:
Hak Soo Choi and John Frangioni of the Beth Israel Deaconess Medical Center in Boston, Mass., wanted to maximize the safety profile of quantum dots—nanoscale semiconductor particles loaded with toxic heavy metals. The researchers injected mice with quantum dots ranging from 1 to 20 nm in diameter and showed that the animals could get rid of dots smaller than 5.5 nm through the kidneys, but larger particles accumulated in the spleen, liver, and lungs.
The impact:
"All the bio-applications of nanotechnology have some problems because of safety issues," says Hitasaka Kobayashi, an imaging scientist at the National Cancer Institute in Bethesda, Md., who was not involved in the research. Thus, this...
The follow-ups:
Kobayashi showed that similar-size constraints determine clearance of branched, star-shaped nanoparticles called dendrimers (Nanomedicine 3:703–17, 2008). Sanjiv Gambhir of Stanford University also measured clearance rates of quantum dots as a function of coating material, size, and length of polymer chain attachments on the outside of the particles (Small, 5:126–34, 2009).
The target:
Choi has unpublished work showing that 70% of his quantum dots can successfully target tumors, whereas earlier reports got at most 10% of the dots to the location of interest. That could boost the effectiveness of quantum dots in cancer treatments and prevent unintended side effects, he says.
| Particle Diameter | % in the liver | % in the lungs | % in the spleen |
| 4.36 nm | 4.5 | <1 | <1 |
| 8.65 nm | 26.5 | 9.1 | 6.3 |
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