title: Comparison of enzyme immobilisation methods for potentiometric phosphate biosensors.
abstract: The development of two phosphate biosensors is described and compared for potentiometric detection of phosphate. Purine nucleoside phosphorylase (PNP) and xanthine oxidase (XOD) were co-immobilised by chemical cross-linking with glutaraldehyde (GLA) and bovine serum albumin (BSA), and via entrapment into polypyrrole (PPy) films by galvanostatic polymerisation. The BSA-GLA film was made with 4.5% v/v GLA and 6.8% w/v BSA with a drying time of 30 min, while polypyrrole entrapment was achieved with 0.5M pyrrole by using a polymerisation time of 200s. A mole ratio of 1:8 (6.2U/mL XOD: 49.6 U/mL PNP) was used for both methods of enzyme immobilisation. Sensitive potentiometric measurements obtained for phosphate with the BSA-GLA-PNP-XOD biosensor were compared with those of PPy-PNP-XOD-Fe(CN)(6)(4-) biosensor. A minimum detectable concentration of 0.1mg/L phosphate and a linear concentration range of 0.5-2.5mg/L were achieved with the PPy-PNP-XOD-Fe(CN)(6)(4-) biosensor. In comparison, a minimum detectable concentration of 2mg/L and a linear concentration range of 4-12 mg/L were achieved with the BSA-GLA immobilisation. The presence of uric and ascorbic acids had the least effect on the performance of the PPy-PNP-XOD-Fe(CN)(6)(4-) biosensor, but will not have any effect on phosphate measurement with both biosensors at levels normally present in water.
authors.affiliation: NanoScience and Sensor Technology Research Group, School of Applied Sciences and Engineering, Monash University, Churchill, Vic 3842, Australia. Abdulazeez.lawal@det.nsw.edu.au
authors.forename: A T
authors.initials: AT
authors.lastname: Lawal
authors.forename: S B
authors.initials: SB
authors.lastname: Adeloju
mesh_terms: D015374:Biosensing Techniques / Q000295:instrumentation*; D004563:Electrochemistry / Q000295:instrumentation*; D004566:Electrodes; D004789:Enzyme Activation; D004800:Enzymes, Immobilized / Q000737:chemistry; D004867:Equipment Design; D019544:Equipment Failure Analysis; D010710:Phosphates / Q000032:analysis* / Q000737:chemistry*; D011683:Purine-Nucleoside Phosphorylase / Q000737:chemistry*; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity; D014159:Transducers; D014969:Xanthine Oxidase / Q000737:chemistry*
chemical_list: D004800:Enzymes, Immobilized; D010710:Phosphates; D014969:Xanthine Oxidase; D011683:Purine-Nucleoside Phosphorylase