The over-abundance or lack of certain types of gut bacteria has been linked to everything from depression to heart disease to childhood asthma. Non-invasively determining which microbes make up a person's "gut microbiome," however, can be difficult – which is why a new 3D-printed capsule was developed.

Created by a team at Massachusetts' Tufts University, the capsule is designed to be orally ingested, collecting various species of bacteria as it passes through the gastrointestinal tract. Once it's excreted in the feces, the capsule can be retrieved and its contents analyzed.

It incorporates two interior chambers that are separated by a semi-permeable membrane. One of these chambers contains helical (helix-shaped) microfluidic channels, in which bacteria gathered from different stages of the GI tract are stored. The other contains calcium salt which produces an osmotic flow across the membrane, pulling bacteria from outside of the capsule into the channels in the first chamber.

The capsule's surface is covered in a pH-sensitive coating, which doesn't dissolve until the capsule has passed through the stomach. This keeps it from collecting bacteria before reaching the small intestine, which is where the real gut microbiome action is. Additionally, a small magnet within the capsule allows it to be manually held at a given point within the GI tract, simply by holding another magnet against the patient's body at that location.

Currently, in order to ascertain which bacteria are present in someone's gut, scientists look for microbial DNA and metabolites within that person's feces. Unlike the case with the capsule, however, this method isn't very good at indicating what the microbiome is like upstream of the distal colon – an area where significantly different species of bacteria may be present.

"We have advanced technologies to analyze bacterial populations using DNA sequencing, but until now have not had a way to sample bacteria throughout the GI tract in a way that is not invasive," says post-doctoral fellow and lead author of a paper on the study, Hojatollah Rezaei Nejad. "By sampling non-invasively, this pill could help us better identify and understand the role of different intestinal bacterial species in health and disease."

So far, the technology has been successfully tested on pigs and non-human primates, but it has yet to be trialled on people. The paper was recently published in the journal Advanced Intelligent Systems.

Source: Tufts University