title: Measurement of protein using an electrochemical bi-enzyme sensor.
abstract: A screen-printed three-electrode amperometric biosensor for the rapid and quantitative measurement of single protein solutions is described. A membrane immobilised protease preparation of broad specificity was used to digest sample protein liberating free amino acids that were subsequently oxidised at a working electrode by immobilised L-amino acid oxidase (L-AAO). The enzymatically generated hydrogen peroxide was determined amperometrically. The fully optimised device required 30 mU L-AAO and 3.94 U protease and had a limit of detection of 170 microg ml(-1) and linearity of response up to 1 mg ml(-1) for Casilan 90 protein. The analytical performance of the device was comparable to that of a commercially available standard photometric protein test kit and required only a 10 microl volume of sample and a single dilution step. Unlike with photometry, the sensor is able to determine the protein content of turbid samples and hence should find widespread applications. The device was simple to use, low-cost and could be mass-produced, yielding results within 4 min of sample addition with acceptable assay repeatability.
authors.affiliation: Cranfield Biotechnology Centre, IBST, Cranfield University at Silsoe, Silsoe, Bedfordshire, MK45 4DT, UK. s.j.setford@cranfield.ac.uk
authors.forename: Steven J
authors.initials: SJ
authors.lastname: Setford
authors.forename: Stephen F
authors.initials: SF
authors.lastname: White
authors.forename: John A
authors.initials: JA
authors.lastname: Bolbot
mesh_terms: D000594:Amino Acid Oxidoreductases / Q000378:metabolism; D015374:Biosensing Techniques / Q000379:methods*; D004563:Electrochemistry; D050830:L-Amino Acid Oxidase; D011506:Proteins / Q000032:analysis*; D011933:Reagent Kits, Diagnostic
chemical_list: D011506:Proteins; D011933:Reagent Kits, Diagnostic; D000594:Amino Acid Oxidoreductases; D050830:L-Amino Acid Oxidase