Application of Prussian Blue modified carbon electrodes for amperometric detection of amyloid-β peptides by flow injection analysis

Non-enzymatic glucose sensing using a nickel hydroxide/chitosan modified screen-printed electrode incorporated into a flow injection analysis system

This works presents a novel screen-printed carbon electrode modified with nickel hydroxide nanoparticles and chitosan (Ni(OH)2/CS/SPCE) for the non-enzymatic flow injection amperometric detection of glucose. The electrode was modified by drop-casting a suspension of the synthesised nanocomposite onto the screen-printed electrode and dried for 1 hour at room temperature. EDX analysis was used to investigate the chemical composition of the electrode before and after modifying. The electrochemical response of the unmodified SPCE and modified electrode was initially investigated by cyclic voltammetry (CV) using 0.1 M NaOH as the supporting electrolyte. CVs showed catalytic activity for glucose oxidation using the Ni(OH)2/CS/SPCE at 0.55 V. During flow injection analysis (FIA), 0.60 V and 1.5 mL min-1 were identified as the optimal potential and flow rate, respectively. A wide linear range of detection was observed (0.2 to 10.0 mM) with a sensitivity and limit of detection of 913 μA mM-1 cm-2 and 0.0174 mM, respectively. The modified electrode also displayed excellent repeatability (RSD = 0.47%, n = 20) and good reproducibility (RSD = 2.52%, n = 6). The modified electrode was shown to be very selectivity for glucose over other interferences commonly found in human blood samples. The practicality of the developed flow injection-amperometric system (FIA-Amp) was validated by the quantification of glucose in real serum samples, where results were in close agreement with those obtained from the local hospital.

Electrochemical Analysis in Studying β-Amyloid Aggregation

β-amyloid (Aβ) is comprised of a group of peptides formed as a result of cleavage of the amyloid precursor protein by secretases. Aβ aggregation is considered as a central event in pathogenesis of Alzheimer's disease, the most common human neurodegenerative disorder. Molecular mechanisms of Aβ aggregation have intensively being investigated using synthetic Aβ peptides by methods based on monitoring of aggregates, including determination of their size and structure. In this review, an orthogonal approach to the study of Aβ aggregation is considered, which relies on electrochemical registration of the loss of peptide monomers. Electrochemical analysis of Aβ (by voltammetry and amperometric flow injection analysis) is based on registration of the oxidation signal of electroactive amino acid residues of the peptide on an electrode surface. The Aβ oxidation signal disappears, when the peptide is included in the aggregate. The advantages and disadvantages of electrochemical analysis for the study of spontaneous and metal-induced aggregation of Aβ, comparative analysis of various peptide isoforms, and study of the process of complexation of metal ions with the metal-binding domain of Aβ are discussed. It is concluded that the combined use of the electrochemical method and the methods based on detection of Aβ aggregates makes it possible to obtain more complete information about the mechanisms of peptide aggregation.