Scientists recently created a new nanotube device containing bismuth to track stem cells by X-ray. Bismuth is used as the active element in a popular stomach-settling elixir and also used in cosmetics and medical applications. Lon Wilson at Rice University and collaborators at University of Houston, St. Luke’s Episcopal Hospital, and the Texas Heart Institute, combined bismuth and the carbon nanotube for the first time to make more effective contrast in CT scan images. The details of the study was buplished in the Journal of Materials Chemistry B.
“At some point, we realized no one has ever tracked stem cells, or any other cells that we can find, by CT,” Wilson said. “CT is much faster, cheaper and more convenient, and the instrumentation is much more widespread (than MRI). So we thought if we put bismuth inside the nanotubes and the nanotubes inside stem cells, we might be able to track them in vivo in real time.”
In the study, they used stem cells derived from pig bone marrow and found that bismuth-filled nanotubes, which they call [email protected], bright stem cells more effectively tracked than common iodine-based contrast agents.
The carbon nanotubes are between 20 and 80 nanometers long and about 1.4 nanometers in diameter. The tubes are made from the chemical process of cutting and purifying. When the tubes and bismuth chloride are mixed in a solution, they combine to form [email protected]. “They’re small enough to diffuse into the cell, where they then aggregate into a clump about 300 nanometers in diameter,” he said. “We think the surfactant used to suspend them in biological media is stripped off when they pass through the cell membrane. The nanotubes are lipophilic, so when they find each other in the cell they stick together.”
Wilson’s lab is now working to double the amount of bismuth in each nanotube. “Bismuth ions appear to get into the nanotubes by capillary action, and we think we can improve on the process to at least double the contrast, maybe more,” he said. “Then we would like to combine both bismuth and gadolinium into one nanotube to produce a bimodal contrast agent that can be tracked with both MRI and CT scanners.”
Photo from http://www.nanotech-now.com