title: Dehydrogenase based reagentless biosensor for monitoring phenylketonuria.
abstract: Phenylketonuria (PKU) is a disease characterized by an inability to metabolize the amino acid l-phenylalanine. The resulting buildup leads to brain damage and ultimately mental retardation in children if their phenylalanine intake is not carefully controlled. The National Institutes of Health recently suggested that people with PKU monitor their phenylalanine levels throughout their life and be put on a low phenylalanine diet. As an alternative approach to analysis using blood, this paper describes the first reagentless dehydrogenase based sensor for the determination of phenylalanine in human urine. The clinical range of phenylalanine in human urine is 20-60mM for people with PKU. Although most clinical analysis is performed using blood, urine was chosen due to its high concentrations of phenylalanine in phenylketonurics, as well as its simple, safe, and painless collection. The sensor is comprised of a carbon paste electrode with nicotinamide adenine dinucleotide (NAD(+)), phenylalanine dehydrogenase (PDH), uricase, and an electron mediator, 3,4-dihydroxybenzaldehyde (3,4-DHB), all mixed into the paste. The electron mediator reacts with the electrode surface to produce two redox species, which catalytically oxidize NADH. The behavior of the electron mediator mixed into a carbon paste electrode has not been previously investigated. Cyclic voltammetry was used to characterize the sensor's response to NADH, and with the addition of PDH and NAD(+) to the paste, its response to phenylalanine in human urine. The limit of detection for phenylalanine is 0.5mM (S/N=3).
authors.affiliation: Department of Chemistry, University of Colorado at Colorado Springs, 1420 Austin Bluffs Parkway, Colorado Springs, CO 80918, United States. dweiss@uccs.edu <dweiss@uccs.edu>
authors.forename: David J
authors.initials: DJ
authors.lastname: Weiss
authors.forename: Megan
authors.initials: M
authors.lastname: Dorris
authors.forename: Amanda
authors.initials: A
authors.lastname: Loh
authors.forename: Laura
authors.initials: L
authors.lastname: Peterson
mesh_terms: D000594:Amino Acid Oxidoreductases / Q000737:chemistry*; D015374:Biosensing Techniques / Q000295:instrumentation* / Q000379:methods; D004563:Electrochemistry / Q000295:instrumentation* / Q000379:methods; D004800:Enzymes, Immobilized / Q000737:chemistry; D004867:Equipment Design; D019544:Equipment Failure Analysis; D006801:Humans; D007202:Indicators and Reagents / Q000737:chemistry; D010649:Phenylalanine / Q000737:chemistry / Q000652:urine*; D010661:Phenylketonurias / Q000175:diagnosis* / Q000652:urine*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D016482:Urinalysis / Q000295:instrumentation* / Q000379:methods
chemical_list: D004800:Enzymes, Immobilized; D007202:Indicators and Reagents; D010649:Phenylalanine; D000594:Amino Acid Oxidoreductases; C022342:phenylalanine oxidase