Construction of a potentiometric biosensor for monitoring urea during peritoneal dialysis

A potentiometric sensor format designed for manufacturability is described. Urease was covalently attached to a commercially available pre-activated membrane. Compression of the immobilized enzyme membrane was used to reduce the thickness and recovery time of the sensor. Thermoplastic was injection molded around a carbon-coated pin leaving a shallow well for deposition of an ammonium ion selective gel. Ultrasonic welding attached the immobilized enzyme membrane over the ion selective electrode. The response characteristics of the sensor were determined in flow injection and stopped-flow fluidic formats. The performance of the sensor was further demonstrated by analyzing urea in peritoneal dialysis fluid from a patient with kidney failure.