Electrochemical Formation of Nanostructured Gold Surfaces on Glassy Carbon for the Determination of Dopamine

Electrochemical Biosensing of Dopamine Neurotransmitter: A Review

Neurotransmitters are biochemical molecules that transmit a signal from a neuron across the synapse to a target cell, thus being essential to the function of the central and peripheral nervous system. Dopamine is one of the most important catecholamine neurotransmitters since it is involved in many functions of the human central nervous system, including motor control, reward, or reinforcement. It is of utmost importance to quantify the amount of dopamine since abnormal levels can cause a variety of medical and behavioral problems. For instance, Parkinson's disease is partially caused by the death of dopamine-secreting neurons. To date, various methods have been developed to measure dopamine levels, and electrochemical biosensing seems to be the most viable due to its robustness, selectivity, sensitivity, and the possibility to achieve real-time measurements. Even if the electrochemical detection is not facile due to the presence of electroactive interfering species with similar redox potentials in real biological samples, numerous strategies have been employed to resolve this issue. The objective of this paper is to review the materials (metals and metal oxides, carbon materials, polymers) that are frequently used for the electrochemical biosensing of dopamine and point out their respective advantages and drawbacks. Different types of dopamine biosensors, including (micro)electrodes, biosensing platforms, or field-effect transistors, are also described.

Methylisothiazolinone response on disposable electrochemical platforms modified with carbon, nickel or gold-based nanomaterials

Screen-printed carbon electrodes (SPCE) were modified with nanocomposite membranes based on polystyrene sulfonate (PSS) or poly(diallyldimethylammonium) (PDDA) matrices and different nanomaterials. Carbon nano-powders (CnP), carbon nano-fibers (CnF) and multi-walled carbon nano-tubes (MWCNTs) were incorporated on PSS matrix. Nickel was incorporated by ion exchange in PSS-CnP composite membranes. Gold nanoparticles (AuNp) were photochemically and electrochemically synthesised and introduced into PDDA membranes. The electrochemical behaviour of methylisothiazolinone (MIT) using these modified electrodes was studied by cyclic voltammetry in 0.1 mol L^-1 NaOH. No electrochemical response is obtained on PSS-nanocarbon transducers at the assayed conditions. The nickel-based transducers allow the MIT identification but not quantification. Using AuNp-based electrochemical transducers, it is observed that in presence of MIT, the electron transfer for AuNp reduction is inhibited, and an oxidation peak appears at + 0.45 V, indicating an interaction between MIT and AuNp on the electrode surface. These facts support the usefulness of the AuNp-based electrodes for the determination of MIT. The intensity of the anodic peak observed at + 0.45 V vs. Ag/AgCl was used as analytical signal for MIT determination. A linear relationship between anodic peak current and MIT concentration is observed in the range 8.7 to 36 mg L^-1 using the transducer prepared by incorporating gold into the PDDA membrane by ion exchange and synthesising AuNp electrochemically. For this electrode, the limit of detection is 2.6 mg L^-1 and the reproducibility, expressed as relative standard deviation (RSD), is lower than 7%. Graphical abstractSchematic representation of the preparation of gold nanoparticles (AuNp) and poly(diallyldimethylammonium) (PDDA)-based platforms and methylisothiazolinone (MIT) electrochemical response on these nanostructured platforms.