Inflammatory bowel disease (IBD) is an autoimmune disorder marked by chronic inflammation of the digestive tract, affecting millions globally with symptoms like severe abdominal pain, rectal bleeding, diarrhea, and weight loss. IBD is triggered when immune cells, specifically macrophages, become overly active and produce high levels of inflammation-inducing proteins known as pro-inflammatory cytokines. These cytokines bind to macrophage receptors, stimulating further cytokine production and perpetuating the inflammation cycle, which results in the debilitating symptoms associated with IBD. Researchers have now developed a novel approach involving a pill that releases microrobots in the colon to combat IBD, which has demonstrated effectiveness in reducing IBD symptoms and promoting the repair of damaged colon tissue in mice, without any toxic side effects.

The microrobots, engineered by scientists at the University of California San Diego (La Jolla, CA, USA), are composed of green algae cells bonded chemically with anti-inflammatory nanoparticles. The nanoparticles capture and neutralize pro-inflammatory cytokines in the gut, while the motile green algae cells distribute the nanoparticles throughout the colon, enhancing cytokine removal and aiding tissue healing. The effectiveness of the nanoparticles lies in their biomimetic design, crafted from biodegradable polymer and coated with macrophage cell membranes to serve as decoys. These decoys attract cytokines without triggering additional cytokine production, thus breaking the inflammatory cycle.

The safety of these biohybrid microrobots has been thoroughly evaluated. Built from biocompatible materials, the green algae used are deemed safe by the U.S. Food and Drug Administration. Encapsulated in a liquid-filled capsule with a pH-responsive coating, the microrobots are protected from stomach acid but released in the colon’s neutral pH, ensuring targeted delivery to the inflammation site. This precision minimizes potential toxicity to other organs. The microrobots remain in liquid form within the capsule until released. When administered orally to mice with IBD, this innovative treatment reduced fecal bleeding, enhanced stool consistency, counteracted weight loss, and reduced colonic inflammation, all without noticeable side effects. The research team is now progressing towards clinical trials of this microrobot treatment.

“The beauty of this approach is that it’s drug-free—we just leverage the natural cell membrane to absorb and neutralize pro-inflammatory cytokines,” said Liangfang Zhang, a professor in the Aiiso Yufeng Li Family Department of Chemical and Nano Engineering at UC San Diego. 

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