Sensitive in vivo detection may support promise for the development of novel biomedical applications, according to study results published in Nov. 7 issue of Nature.

Carbon nanotubes (CNTs) have been explored for many applications, including their use as scaffolds for cells in tissue engineering. In regards to biocompatibility, non-toxicity and non-carcinogenicity, CNTs are still unclear. One limiting factor of toxicological studies has been the use of animal tissue rather than living specimen. Researchers have now detected single-walled CNTs (SWCNTs) inside living animals, with benign results, which pave the way for future research on the fate of nanotubes inside living organisms.

R. Bruce Weisman, MD, a professor in the department of chemistry at Rice University in Houston, and his colleagues investigated the spectroscopy and photophysics of fullerenes and carbon nanotubes.

In the study, fruit fly larvae were raised on a yeast paste that contained carbon nanotubes. The flies were fed the paste from the time they hatched throughout their initial feeding phase of four to five days. Fruit flies are ravenous eaters during this period and gain weight continuously until they are about 200 times heavier than hatchlings. Then they become pupae and mature inside pupal cases, emerging as adult flies, according to Weisman.

Among Weisman’s findings were:

• Dispersed SWCNTs in the food supply of fruit fly larvae have no adverse effects on their survival to adult-stage flies or on their developmental weight gain;
• SWCNTs can be noninvasively detected in living animals (fly larvae) by imaging the nanotubes, which is characteristic of near-infrared fluorescence emission;
• Under the microscope, the approach lets them image individual SWCNTs in dissected tissue specimens; and
• Only a very tiny fraction of the ingested SWCNTs became incorporated into tissues of the fly larvae; almost all seem to have passed harmlessly through the digestive system.

The study addresses two issues relevant to future biomedical applications of SWCNTs. Weisman said that "it demonstrates that near-infrared fluorescence is a highly effective probe for disaggregated SWCNTs in biological tissues and organisms. It can detect, image, and structurally identify individual nanotubes in tissue specimens and can nondestructively image accumulations of nanotubes inside living organisms.” He added that the study “provides new results on the effect of SWCNTs on intact organisms, relevant to possible medical uses and also to environmental contamination concerns.”