Ammonia Dynamics in the Human Body: Insights in Biomedical Sensing Technologies

Advancements in sensor technologies capable of measuring key biomarkers can greatly enhance medical diagnostics and health monitoring, facilitating more effective diagnosis, treatment, and prevention. While there are numerous biomarkers of interest, gaseous ammonia (NH₃) stands out due to its significance as an indicator of organ function (e.g., liver and kidney failure) or bacterial infections (e.g., Helicobacter pylori, Proteus mirabilis) in the body. This review discusses the metabolism and presence of NH₃ in body organs, as well as clinical conditions associated with the regulation of NH₃ concentrations. This paper reviews various sensing materials and parameters, along with current state-of-the-art gas sensors capable of detecting NH₃ for biomedical applications. Additionally, it addresses the challenges faced by biomedical sensing technologies already in use in medical applications. This review highlights that while NH₃ sensing applications for breath analysis are already well-developed, in vivo NH₃ sensing remains in its early stages and faces significant challenges. Finally, promising future research directions for NH₃ sensing are discussed, including the integration of NH₃ sensors in catheters or in the Simulator of Human Intestinal Microbial Ecosystem, as well as the early detection of antibiotic-resistant bacteria to enhance medical diagnostics.