Silicon QDs Could be Safe for Deep-Tissue Imaging


201306047919620BUFFALO, N.Y., Aug. 8, 2013 — Monkeys injected with large doses of silicon nanocrystals displayed no adverse health effects three months later, a promising step forward in the potential development of human biomedical imaging applications.
The University at Buffalo (UB) study with nonhuman primates suggests that the silicon nanocrystals, or quantum dots, may be a safe tool for diagnostic imaging in humans. The nanocrystals absorb and emit light in the near-IR, making them preferable over traditional fluorescence-based techniques for seeing deeper into tissue.

Bright-light emission from silicon quantum dots in a cuvette. The image is from a camera that captures the near-IR light that the quantum dots emit. The light emission shown is a pseudo color, as near-IR light does not fall in the visible spectrum. Courtesy of Folarin Erogbogbo. 

Quantum dots, or nanocrystals, are very, very promising for biomedical imaging applications, but everyone’s worried about the toxicity and what will happen to them if they degrade,” said research assistant professor Folarin Erogbogbo, co-lead author of the study. “Silicon nanocrystals can be the solution to that because they don’t contain materials like cadmium that are found in other quantum dots, and are generally considered to be nontoxic.”


The researchers tested the silicon quantum dots in rhesus macaques and mice, injecting each animal with 200 mg of the particles per kilogram of the animal’s weight. Blood tests taken for three months afterward showed no signs of toxicity in either animal, although the mice experienced inflammation and the spotty death of liver cells as a result of the silicon crystals gathering and remaining in their livers and spleens; the monkeys’ organs, however, remained normal.


Researchers capped the surface of the quantum dots with organic molecules to keep the crystals from degrading too fast, which could help explain the lack of toxicity found in the animals’ blood.


The study, a collaboration between UB, Chinese People’s Liberation Army General Hospital in China, San Jose State University, Nanyang Technological University in Singapore, and Korea University in South Korea, is part of a larger body of research investigating the effect of various nanoparticles in animal models.
The study was published in ACS Nano (doi: 10.1021/nn4029234).
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