An ingestible bacterial-electronic system to monitor gastrointestinal health

Abstract

Biomolecular monitoring in the gastrointestinal tract could offer rapid, precise disease detection and management but is impeded by access to the remote and complex environment. Here, we present an ingestible micro-bio-electronic device (IMBED) for in situ biomolecular detection based on environmentally resilient biosensor bacteria and miniaturized luminescence readout electronics that wirelessly communicate with an external device. As a proof of concept, we engineer heme-sensitive probiotic biosensors and demonstrate accurate diagnosis of gastrointestinal bleeding in swine. Additionally, we integrate alternative biosensors to demonstrate modularity and extensibility of the detection platform. IMBEDs enable new opportunities for gastrointestinal biomarker discovery and could transform the management and diagnosis of gastrointestinal disease.

Fig. 1.. Probiotic E. coli can be engineered to sense blood in vitro and in vivo.

(A) Schematic of the blood sensor gene circuit. Extracellular heme is internalized through the outer-membrane transporter ChuA and interacts with the transcriptional repressor HtrR to allow for expression of the bacterial luciferase operon luxCDABE. (B) Dose-response curves of prototype (V1) and optimized (V2) heme-sensing genetic circuits in laboratory (MG1655) and probiotic (Nissle) strains of E. coli. Error bars represent SEM of three independent biological replicates. (C) In vivo blood sensor performance. C57BL/6J mice were administered indomethacin (10 mg/kg) to induce gastrointestinal bleeding or vehicle (PBS, phosphate-buffered saline) and inoculated with blood sensor E. coli Nissle cells the following day. Normalized luminescence values of fecal pellets were significantly higher in mice administered indomethacin compared to control animals (*P = 0.04; Student’s t test; N = 10 mice). CFU, colony-forming units; RLU, relative luminescence units.

Fig. 2.. Design and in vitro evaluation of IMBED for miniaturized wireless sensing with cellular biosensors.

(A) Cross section, electrical system diagram, and front- and back-side photos of the device. PDMS, polydi-methylsiloxane. (B) System photocurrent response measured without cells. The incident photon flux was supplied by green light-emitting diode (wavelength λ = 525 nm) and calibrated with an optical power meter (individual traces shown for N = 3 devices). (C) Kinetic response of blood sensor IMBED in bacterial growth media supplemented with 0 and 500 ppm blood. (D) Dose-response of blood sensor IMBEDs in bacterial growth media containing different blood concentrations 2 hours after exposure. The leftmost data point represents the background response in the absence of blood. (E) Detection of multiple gut-relevant small molecules with IMBEDs. HrtR-, LuxR- and ThsRS-containing E. coli Nissle strains in IMBEDs were exposed to 500 ppm blood, 100 nM acyl-homoserine lactone (AHL), or 10 mM thiosulfate for 2 hours. In (C) to (E), error bars denote the SEM for three independent biological replicates conducted with different IMBEDs. *P < 0.05, **P < 0.01, Student’s t test.

Fig. 3.. IMBEDs can rapidly detect porcine gastric bleeding.

(A) Schematic of the experimental flow, which consisted of blood administration in neutralization solution, capsule deposition, and wireless transmission to a commercial receiver connected to a laptop or a cellular phone. Representative endoscopic (B) and x-ray (C) images illustrate the location of the device in the stomach at the conclusion of our 2-hour experiments, just before device removal [scale bar (C), 5 cm]. (D) Kinetic response of blood sensor IMBED in a porcine model of gastric bleeding. IMBEDs deposited in gastric cavity can rapidly discriminate between pigs administered blood versus buffer control. Error bars denote SEM for six IMBED experiments (three animals on different days, two capsules per animal). *P < 0.05, Student’s t test. (E) Receiver operating characteristic (ROC) of IMBED sensing over time. Perfect detection is achieved at t = 120 min. AUC, area under the curve.