News | August 14, 2014

New Imaging Agent Provides Better Picture of the Gut

Applying a method that uses nanoparticles to create visual contrast, a researcher created the above photoacoustic image of a mouse intestine. The colors indicate the depth of the intestine (red: deep blue: shallow). Photo courtesy Jonathan Lovell.

August 14, 2014 — A multi-institutional team of researchers has developed a new nanoscale agent for imaging the gastrointestinal (GI) tract. This safe, noninvasive method for assessing the function and properties of the GI tract in real time could lead to better diagnosis and treatment of gut diseases.

Illnesses such as small bowel bacterial overgrowth, irritable bowel syndrome and inflammatory bowel disease all occur in the intestine and can lead to serious side effects in patients with diseases such as diabetes and Parkinson’s. Until now, there has yet to be an effective way to functionally image the intestine. However, in a paper published July 6 in the journal Nature Nanotechnology, the researchers demonstrated that through a complementary approach using photoacoustic imaging and positron emission tomography (PET), they have created a multimodal functional imaging agent that could be used to perform noninvasive functional imaging of the intestine in real time.

Weibo Cai, an associate professor of radiology, medical physics and biomedical engineering at the University of Wisconsin-Madison, worked collaboratively with Jonathan Lovell, an assistant professor of biomedical engineering at the State University of New York at Buffalo, and Chulhong Kim, an assistant professor of creative information technology engineering at Pohang University of Science and Technology in South Korea. The team developed a family of nanoparticles that can provide good optical contrast for imaging, yet avoid absorption into the body and withstand the harsh conditions of the stomach and intestine.

Currently, patients drink barium and technicians view the intestine through X-rays and ultrasound. These methods, however, have many limitations, including accessibility and radiation exposure.

The researchers' nanoparticles contain bright dyes. Patients still will drink a liquid, but it will contain the nanoparticles and allow an imaging technician to noninvasively view the illuminated intestine with photoacoustic imaging. “We can actually see the movement of the intestine in real time,” Lovell said.

Cai and Lovell worked collaboratively to use two imaging techniques. Cai specializes in PET imaging, while Lovell and Kim’s expertise is in photoacoustic imaging, a technique that draws on ultrasound to generate high-definition images through light-based imaging.

While photoacoustic techniques yield high-definition images, PET imaging can penetrate deeper and image the entire body. Combining the two delivers the most information possible: high-definition images, images deep inside the body and a view of the intestine in relation to the entire body.

So far, the researchers have conducted successful test trials in mice and are hoping to move to human trials soon. “This is one of the first studies using both imaging techniques,” Cai said. “The two imaging techniques work well together and get us all of the information that we need.”

Cai hopes the imaging agent can be targeted to look for certain disease-related markers and be used in therapeutic applications in the near future. “It is everything I would hope for in an imaging agent, and it is safe since we use U.S. Food and Drug Administration (FDA)-approved agents to make these nanoparticles. That is why I am so excited about this,” he said. “These are the promising first steps.”

Grants from the National Institutes of Health, the U.S. Department of Defense and the Korean Ministry of Science funded the research. Additional authors on the paper include Yumiao Zhang, Mansik Jeon, Laurie J. Rich, Hao Hong, Jumin Geng, Yin Zhang, Sixiang Shi, Todd E. Barnhart, Paschalis Alexandridis, Jan D. Huizinga and Mukund Seshadri.

For more information: www.news.wisc.edu

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