Point-of-Care Blood Ammonia Measurement Using a Gas-Phase Fuel Cell Sensor

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Project Summary: Measurement of blood ammonia from a finger or heel stick The goal is to develop a portable device that measures ammonia levels in blood obtained by finger or heel stick, in the same way that diabetics measure their blood sugar levels. PAD will instantly diagnose elevated blood ammonia (hyperammonemia), thus triggering treatment, and preventing ammonia-induced brain damage. PAD will permit finger and heel sticks, sparing children the trauma of venipuncture, and requires only 0.02 ml (20 µL) blood volumes, conserving the blood of tiny infants. By contrast, the standard clinical laboratory test requires: proximity to a central laboratory (usually in a hospital) and 1 to 2 hours of turn-around time; intravenous cannulation by a trained phlebotomist; and at least 3 ml of blood, or 300-fold more blood than PAD. PAD can have a major impact on child health. Rapid diagnosis and close monitoring of blood ammonia will guide treatments, from emergency hemodialysis, to intravenous ammonia scavengers, to home medications. Hyperammonemia presents a risk to both child and adult populations in the U.S.: (1) 20,000 children with mutations in any one of 44 genes; (2) 400,000 preterm infants born annually before 37 weeks with immature livers; (3) 630,000 adults with liver cirrhosis; (4) 140,000 cancer patients receiving 5- fluorouracil chemotherapy; and (5) 6 million adults with obesity-associated nonalcoholic steatohepatitis (NASH). PAD uses a novel technology that adapts an inexpensive ($190) commercially available fuel cell gaseous ammonia detector for use with blood using a consumable cartridge containing K2CO3 to liberate gaseous ammonia from the sample. Rapid diagnosis by PAD will protect brain function in many children. Treatment will improve when PAD is deployed to the bedside and outpatient clinics. Aim 1. Create and validate a cartridge production system capable of producing cartridges suitable for clinical studies Our specific aim is to develop an in-house cartridge production and assembly process that can produce lot sizes of >5,000 cartridges that show less than 15% variability in K2CO3 loading and provide an ammonia limit of quantification of ≤20 µM. 1