  A perturbed gut microbiome has recently been linked with multiple disease
processes, yet researchers currently lack tools that can provide in vivo,
quantitative, and real-time insight into these processes and associated
host-microbe interactions. We propose an in vivo wireless implant for
monitoring gastrointestinal tract redox states using oxidation-reduction
potentials (ORP). The implant is powered and conveniently interrogated via
ultrasonic waves. We engineer the sensor electronics, electrodes, and
encapsulation materials for robustness in vivo, and integrate them into an
implant that endures autoclave sterilization and measures ORP for 12 days
implanted in the cecum of a live rat. The presented implant platform paves the
way for long-term experimental testing of biological hypotheses, offering new
opportunities for understanding gut redox pathophysiology mechanisms, and
facilitating translation to disease diagnosis and treatment applications.
