Bioengineers have found a way to visualize the action of the gastrointestinal tract in real-time, developing a non-invasive means to observe the wave-like muscle contractions that occur during peristalsis.
According to the NIH Director’s blog, new technologies are needed to aid in diagnosis and treatment of the wide range of disorders that affect gastrointestinal motility. In a search for better imaging methods, Jonathan Lovell (University at Buffalo), a recipient of the NIH Director’s Early Independence Award, began investigating the optical properties of a family of dyes called naphthalocyanines.
In a Nature Nanotechnology article, Lovell and colleagues describe their development of nanoparticles that can withstand the harsh conditions of the stomach and intestine, avoid systemic absorption, and provide good optical contrast for photoacoustic imaging.
The authors exploited the hydrophobicity of the naphthalocyanine dyes to generate purified frozen micelles of about 20 nm, which they called “nanonaps”. Nanonaps can be suspended in water, which Lovell et al. call “nanojuice”, and swallowed. Unlike conventional chromophores, nanonaps have non-shifting spectra at ultra-high optical densities.
The engineers tested the nanojuice in conjunction with photoacoustic tomography, which emits laser pulses that excite the nanonaps. The pulses can penetrate up to 5 cm in tissue and are harmless. As the nanonaps respond, ultrasound is used to detect their vibrations, producing an image.
Mice drank the nanojuice after fasting for 12 hours. The authors found that the nanonaps were safe and passed through the mice without any absorption into the bloodstream. Lovell and colleagues showed that they could use this method to detect blockages in the gastrointestinal tracts of the mice, and—importantly—to capture real-time images of peristalsis in the small intestine.
In the research article, Lovell and colleagues report that they were able visualize the intestinal distribution of the nanonaps with low background and remarkable resolution, allowing for real-time imaging of intestinal function. Positron emission tomography following nanonap radiolabelling allowed for complementary whole-body imaging.
According to the NIH Director’s Blog, Lovell’s group has developed 4 “flavors” of nanojuice, each responding to a different wavelength of laser light.
They hope to use the different nanojuices to detect different disorders (bacterial infections, inflammatory bowel disease, irritable bowel syndrome, or even neurologic conditions). The nanojuices might even be used simultaneously, to screen the gastrointestinal tract for a variety of disorders.