Figure 1.

Design and mechanism of the magnetic living hydrogels localized and retained in the intestine. a) The magnetic living hydrogel is orally administrated and retained in the intestine by a magnet worn on the abdominal skin. Inset: magnetized NdFeB microparticles incorporated in the hydrogel matrix provide the attractive magnetic force between the magnetic hydrogel and wearable magnet for intestinal localization and retention. b) The hydrogel matrix is physically crosslinked by nanocrystalline domains and reinforced by NdFeB microparticles, making it mechanically tough. c) Living synthetic microbes encapsulated in the hydrogel matrix interact with the gut microbiota when the magnetic hydrogel is retained in the gut, enabling biological functions such as sensing and releasing. d) Intestinal peristalsis propels a food bolus along the intestinal lumen, while the magnetic hydrogel can be retained due to the magnetic attraction with the wearable magnet. e) Intestinal segmentation breaks a food bolus into fragments in the intestinal lumen, while the magnetic hydrogel can remain intact due to its mechanical toughness.