Scientists are developing innovative ingestible devices, including battery-free robotic interfaces (IngRI) and electroceutical capsules, to address various gastrointestinal conditions. These devices aim to improve upon existing ingestible electronics by tackling challenges such as poor electrode-tissue contact, limited navigation, short dwell times, and inadequate battery life. The IngRI, for instance, uses thin-film circuits embedded in an elastomer, conforming to the gastric mucosa and adhering for up to 48 hours. It is powered wirelessly via near-field inductive coupling operating near 13.56 MHz, eliminating the need for internal batteries, which often consume over 50% of an ingestible device's volume and pose risks in corrosive gastric environments.
One significant application of these ingestible devices is the regulation of hormones, particularly ghrelin, known as the "hunger hormone." In swine models, activating the IngRI to deliver short-pulse electrostimulation (approximately 0.5 mA, 14 Hz, 0.33 ms pulse width) led to a significant increase in plasma ghrelin levels, roughly doubling from 93.9 pg/mL to 181.4 pg/mL within 10 minutes. This increase was sustained for 30 minutes of stimulation and rapidly dissipated once the device was turned off. Similar results were observed with a CMOS-based ingestible capsule, demonstrating a 30% increase in ghrelin levels.
These advancements offer a non-invasive alternative to surgically implanted gastric stimulators, which are the current clinical standard. The ability of devices like IngRI to provide chronic stimulation for several days, compared to the 15-30 minute battery life of some contemporary ingestibles like RoboCap and STIMS, significantly enhances their therapeutic potential. Researchers anticipate that future iterations could have even longer lifespans, extending to weeks or months, and integrate sensors for closed-loop neuromodulation. The clinical potential of these devices includes treating conditions such as cachexia, anorexia, and other endocrine issues by modulating appetite and hormone release, with human trials anticipated within three years.
MIT engineers, for example, have shown that an ingestible capsule delivering electrical current can stimulate endocrine cells to produce ghrelin. This approach is seen as a way to utilize the body's own systems to release hormones, rather than introducing external agents. The devices are also being explored for their potential in treating gastroparesis by influencing the enteric nervous system. Initial tests on animals showed no significant inflammation or adverse effects, suggesting a safe method for long-term gastric stimulation.
