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.

Multifunctional biosensors based on peptide–polyelectrolyte conjugates

“…The results confirmed that the hexagonal phase is indeed P61, and the orthorhombic is P22121, 8,20 as shown in Figure 2A. By means of Rietveld refinements ( Figure S1-S4, presented as Supporting Information material), 37, 38 the presence of MP11 was clearly evidenced and the main characteristic peaks -found in both phases -are indicated by arrows in Figure 2A.…”

“…Another scenario is that since PAH does not cover the FF-MNSs it is more susceptible to dissolution, as seen in some reports where FF-MNSs dissolves in phosphate buffer solution. 8,[49][50][51] Following the characterization, the kinetics of the reaction can be described by the equation (6):…”

“…[19][20][21] However, when FF is self-assembled under anhydrous conditions, they are frequently described in terms of orthorhombic groups. 5,6,8 Similarly, hydrated FF nanotubes exhibit a hexagonal to orthorhombic phase transition when incubated at temperatures above 140 °C. This phenomenon has been ascribed to the release of water and the change in peptide backbones from a linear conformation to a cyclic one, followed by the reorganization of the crystalline structure in the orthorhombic symmetry group P22121.…”

“…20 The observed transition is irreversible, and induces strong modifications on L,L,-diphenylalanine micro-/nanostructures (FF-MNSs) properties, ranging from the nanoscopic to the macroscopic level. 6,8,22 Clearly, this realignment at the molecular level affects the balance of interactions.…”

A Peptide‐Based Electrochemical Biosensor for Facile Measurement of Whole‐Blood Heparin

“…This contribution is actually the first to report a novel electrochemical biosensor for measurement of whole‐blood heparin based on heparin‐binding peptide. In recent years, peptides have been used frequently for biosensor fabrication because of their potent binding affinity towards specific analytes, high biological compatibility, and high solubility in aqueous solutions . Heparin specialized binding peptide from the G domain of the laminin α1 chain has been rationally designed to construct the electrochemical biosensor, which exhibits considerable binding affinity and specificity towards heparin …”