News | September 05, 2013

Bismuth-Carrying Nanotubes Show Promise for CT Scans

Rice-led collaboration finds element useful as contrast agent for tracking stem cells

An electron microscope image shows bismuth ions (dark lines) sitting inside carbon nanotubes.

An electron microscope image shows bismuth ions (dark lines) sitting inside carbon nanotubes.

September 5, 2013 — Scientists at Rice University have trapped bismuth in a nanotube cage to tag stem cells for X-ray tracking. Bismuth is probably best known as the active element in a popular stomach-settling elixir and is also used in cosmetics and medical applications. Rice chemist Lon Wilson and his colleagues are inserting bismuth compounds into single-walled carbon nanotubes to make a more effective contrast agent for computed tomography (CT) scanners. Details of the work by Wilson's Rice team and collaborators at the University of Houston, St. Luke's Episcopal Hospital and the Texas Heart Institute appear in the Journal of Materials Chemistry B.

This is not the first time bismuth has been tested for CT scans, and Wilson's lab has been experimenting for years with nanotube-based contrast agents for magnetic resonance imaging (MRI) scanners. But this is the first time anyone has combined bismuth with nanotubes to image individual cells, he said.

"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."

Experiments to date confirm their theory. In tests using pig bone marrow-derived mesenchymal stem cells, Wilson and lead author Eladio Rivera, a former postdoctoral researcher at Rice, found that bismuth-filled nanotubes, which they call [email protected]-tubes, produce CT images far brighter than those from common iodine-based contrast agents.

"Bismuth has been thought of before as a CT contrast agent, but putting it in nanotube capsules allows us to get them inside cells in high concentrations," Wilson said. "That lets us take an X-ray image of the cell."

The capsules are made from a chemical process that cuts and purifies the nanotubes. When the tubes and bismuth chloride are mixed in a solution, they combine over time to form [email protected]-tubes. The nanotube capsules are between 20 and 80 nanometers long and about 1.4 nanometers in diameter.

"They're small enough to diffuse into the cell, where they then aggregate into a clump about 300 nanometers in diameter," said Wilson. "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 said his team's studies showed stem cells readily absorb [email protected]-tubes without affecting their function. "The cells adjust over time to the incorporation of these chunks of carbon and then they go about their business," he said.

[email protected]-tubes have clear advantages over commonly used iodine-based contrast agents, Wilson said. "Bismuth is a heavy element, down near the bottom of the periodic table, and more effective at diffracting X-rays than almost anything else you could use," he said. Once the bismuth is encapsulated in the nanotubes, the agent can produce high contrast in very small concentrations. The nanotube surfaces can be modified to improve biocompatibility and their ability to target certain types of cells. They can also be modified for use with MRI, positron emission tomography (PET) and electron paramagnetic resonance imaging systems.

The Rice lab is currently 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," Wilson 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."

For more information: www.rice.edu

Related Content

Guerbet announced the launch of OptiProtect 3S, a new range of technical services for its injection solutions. OptiProtect 3S is designed to support imaging centers in the daily use and protection of their injection solutions.
News | Contrast Media Injectors | February 25, 2021
February 25, 2021 — Guerbet announced the launch of ...
icobrain cva allows the quantitative assessment of tissue perfusion by reporting the volume of core and perfusion lesion by quantifying Tmax abnormality and CBF abnormality together with the mismatch volume and ratio
News | Artificial Intelligence | February 23, 2021
February 23, 2021 — icometrix, world leader in imaging...
Examples of the imaging performance of XPCI-CT (b,e) compared to conventional specimen radiography (a,d) and benchmarked against histopathology (c,f). he top row focuses on the similarity between the XPCI-CT slice in (b) and the histological slice in (c). Arrow 1 indicates margin involvement, arrow 2 a variation in density in the internal structure of the tumour mass, arrow 3 tumour-induced inflammation. All this is confirmed by the histological slice in (c), and hardly visible in the conventional image in

Examples of the imaging performance of XPCI-CT (b,e) compared to conventional specimen radiography (a,d) and benchmarked against histopathology (c,f). he top row focuses on the similarity between the XPCI-CT slice in (b) and the histological slice in (c). Arrow 1 indicates margin involvement, arrow 2 a variation in density in the internal structure of the tumour mass, arrow 3 tumour-induced inflammation. All this is confirmed by the histological slice in (c), and hardly visible in the conventional image in (a). The bottom row focuses on the detection of small calcifications, a key feature in DCIS. These are undetectable in (d), detected in (e), enhanced in the maximum intensity projection (MIP) image at the bottom of (f), and confirmed by histopathology in the top part of (f). The scale bar [shown in (b) and (e)] is the same for all images apart from (f), which has its own scale. Red arrows in (e) and (f) indicate the microcalcifications. Image courtesy of Professor Alessandro Olivo

News | Breast Imaging | February 22, 2021
February 22, 2021 — A new X-ray imaging scanne
Dr Sahar Saleem placing the mummy in the CT scanner

Dr. Sahar Saleem placing the mummy in the CT scanner. Image courtesy of Sahar Saleem

News | Computed Tomography (CT) | February 22, 2021
February 22, 2021 — Modern medical technology is helping scholars tell a more nuanced story about the fate of an anci
Unhealthy lifestyles, various diseases, stress, and aging can all contribute to an imbalance between the production of ROS and the body's ability to reduce and eliminate them. The resulting excessive levels of ROS cause "oxidative stress".

Unhealthy lifestyles, various diseases, stress, and aging can all contribute to an imbalance between the production of ROS and the body's ability to reduce and eliminate them. The resulting excessive levels of ROS cause "oxidative stress". Graphic courtesy of National Institutes for Quantum and Radiological Science and Technology

News | Magnetic Resonance Imaging (MRI) | February 10, 2021
February 10, 2021 — Oxygen is essential for human life, but within the body, certain biological environmental conditi
Materialise engineers coordinated the development of a surgical plan and created an on-screen 3D model based on CT-scans.

Materialise engineers coordinated the development of a surgical plan and created an on-screen 3D model based on CT-scans.

Feature | Medical 3-D Printing | February 03, 2021
Three-dimensional technologies, developed by Materialise
Kaplan–Meier curves for the high-risk individuals and the ones with low or medium risk according to AI-severity. The threshold to assign individuals into a high-risk group was the 2/3 quantile of the AI-severity score computed for patients of the KB development cohort. a Kaplan–Meier curves were obtained for the 150 leftover KB patients from the development cohort. b Kaplan–Meier curves were obtained for the 135 patients of the IGR validation cohort. p-values for the log-rank test were equal to 4.77e–07 (KB

Kaplan–Meier curves for the high-risk individuals and the ones with low or medium risk according to AI-severity. The threshold to assign individuals into a high-risk group was the 2/3 quantile of the AI-severity score computed for patients of the KB development cohort. a Kaplan–Meier curves were obtained for the 150 leftover KB patients from the development cohort. b Kaplan–Meier curves were obtained for the 135 patients of the IGR validation cohort. p-values for the log-rank test were equal to 4.77e–07 (KB) and 4.00e–12 (IGR). The two terciles used to determine threshold values for low-, medium-, and high-risk groups were equal to 0.187 and 0.375. Diamonds correspond to censoring of patients who were still hospitalized at the time when data ceased to be updated. The bands correspond to the sequence of the 95% confidence intervals of the survival probabilities for each day. KB Kremlin-Bicêtre hospital, IGR Institut Gustave Roussy hospital. Courtesy of Nature Communications.

News | Coronavirus (COVID-19) | February 01, 2021
February 1, 2021 — COVID-19...