title: A nonenzymatic biosensor based on gold electrodes modified with peptide self-assemblies for detecting ammonia and urea oxidation.
abstract: We have developed a nonenzymatic biosensor for the detection of ammonia and urea oxidation based on the deposition of peptide microstructures onto thiolated gold electrodes. FF-MNSs/MCP/Au assemblies were obtained by modifying gold substrates with 4-mercaptopyridine (MCP), followed by coating with l,l-diphenylalanine micro/nanostructures (FF-MNSs) grown in the solid-vapor phase. Benzene rings and amide groups with peptide micro/nanostructures interact with synthetic NH4(+) receptors through cation-π and hydrogen bonding. AuOH clusters on the Au surface provided the catalytic sites. The application of a predetermined concentration of analytes at the peptide interfaces activated the catalytic sites. We observed a relationship between the stability of films and the crystal structure of peptides, and we organized the FF-MNSs into an orthorhombic symmetry that was the most suitable assembly for creation of our biosensors. At 0.1 mol L(-1) NaOH, these FF-MNSs/MCP/Au electrodes have electrocatalytic properties regarding ammonia and urea oxidation that are comparable to those of enzyme-based architectures. Under optimal conditions, the electrocatalytic response is proportional to the ammonia and urea concentration in the range 0.1-1.0 mmol L(-1). The sensitivity was calculated as 2.83 and 81.3 μA mmol L(-1) cm(-2) for ammonia and urea, respectively, at +0.40 V (vs SCE). Our detection method is easy to follow, does not require a mediator or enzyme, and has strong potential for detecting urea via nonenzymatic routes.
authors.affiliation: Centro de Ciências Naturais e Humanas, Universidade Federal do ABC , 09210-580 Santo André, SP Brazil.
authors.forename: Roberta C
authors.initials: RC
authors.lastname: Bianchi
authors.forename: Emerson Rodrigo
authors.initials: ER
authors.lastname: da Silva
authors.forename: Luiz H
authors.initials: LH
authors.lastname: Dall'Antonia
authors.forename: Fabio Furlan
authors.initials: FF
authors.lastname: Ferreira
authors.forename: Wendel Andrade
authors.initials: WA
authors.lastname: Alves
mesh_terms: D000641:Ammonia / Q000032:analysis* / Q000737:chemistry*; D015374:Biosensing Techniques; D055664:Electrochemical Techniques; D004566:Electrodes; D006046:Gold / Q000737:chemistry*; D010084:Oxidation-Reduction; D010316:Particle Size; D010455:Peptides / Q000138:chemical synthesis* / Q000737:chemistry; D013499:Surface Properties; D014508:Urea / Q000032:analysis* / Q000737:chemistry*
chemical_list: D010455:Peptides; D006046:Gold; D000641:Ammonia; D014508:Urea