Application of nanosized gold and graphene modified carbon ionic liquid electrode for the sensitive electrochemical determination of folic acid

Efficient Electrochemical Sensor Based on Gold Nanoclusters/Carbon Ionic Liquid Crystal for Sensitive Determination of Neurotransmitters and Anti-Parkinson Drugs

Purpose: Herein we introduce a simple and sensitive sensor for the electrochemical determination of neurotransmitters compounds and anti-Parkinson drugs.

Methods: The electrochemical sensor (Au/CILCE) based on gold nanoclusters modified carbon ionic liquid crystal (ILC) electrode was characterized using scanning electron microscopy and voltammetry measurements.

Results: The effect of ionic liquid type in the carbon paste composite for the electro-catalytic oxidation of L-dopa was evaluated. Highest current response was obtained in case of ILC compared to other studied kinds of ionic liquids. The effective combination of gold nanoclusters and ILC resulted in extra advantages including large surface area and high ionic conductivity of the nanocomposite. L-dopa is considered one of the most important prescribed medicines for treating Parkinson’s disease. Moreover, a binary therapy using L-dopa and carbidopa proved effective and promising as it avoids the short comings of L-dopa mono-therapy for Parkinson’s patients. The Au/CILCE can detect L-dopa in human serum in the linear concentration range of 0.1 μM to 90 μM with detection and quantification limits of 4.5 nM and 15.0 nM, respectively. Also, the Au/CILCE sensor can simultaneously and sensitively detect L-dopa in the presence of carbidopa with low detection limits.

Conclusion: The sensor is advantageous to be applicable for electrochemical sensing of other biologically electroactive species.

A Review: New Trends in Electrode Systems for Sensitive Drug and Biomolecule Analysis

Drug and biomolecule analysis with high precision, fast response, not expensive, and user-friendly methods have been very important for developing technology and clinical applications. Electrochemical methods are highly capable for assaying the concentration of electroactive drug or biomolecule and supply excellent knowledge concerning its physical and chemical properties such as electron transfer rates, diffusion coefficients, electron transfer number, and oxidation potential. Electrochemical methods have been widely applied because of their accuracy, sensitivity, cheapness, and can applied on-site determinations of various substances. The progress on electronics has allowed developing reliable, more sensitive and less expensive instrumentations, which have significant contribution in the area of drug development, drug and biomolecule analysis. The developing new sensors for electrochemical analysis of these compounds have growing interest in recent years. Screen-printed based electrodes have a great interest in electrochemical analysis of various drugs and biomolecules due to their easy manufacturing procedure of the electrode allow the transfer of electrochemical laboratory experiments for disposable on-site analysis of some compounds. Paper based electrodes are also fabricated by new technology. They can be preferred due to their easy, cheap, portable, disposable, and offering high sensitivity properties for many application field such as environmental monitoring, food quality control, clinical diagnosis, drug, and biomolecules analysis. In this review, the recent electrochemical drug and biomolecule (DNA, RNA, µRNA, Biomarkers, etc.) studies will be presented that involve new trend disposable electrodes.

Voltammetric sensing performances of a carbon ionic liquid electrode modified with black phosphorene and hemin

A black phosphorene (BPE) and poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS) hybrid was used for the immobilization of hemin on a carbon ionic liquid electrode (CILE). BPE inside the PEDOT:PSS film was stable without adverse effects of water and oxygen. The hemin-modified electrode facilitates electrochemical communication with a couple of well-shaped and enhanced redox waves. Therefore BPE exhibits an accelerating function to the electron movement. This sensor exhibits excellent electrocatalytic effects on the reduction of various substrates including trichloroacetic acid (TCA), nitrite and H₂O₂. As for TCA, the reduction current at -0.36 V (vs. Ag/AgCl) increases linearly in the concentration range from 2.0 to 180 mmol·L^-1 with a detection limit of 0.67 mmol·L^-1 (at 3σ). As for nitrite, the reduction current at -0.59 Vis linear in the 1.0 to 10.5 mmol·L^-1 concentration range, and the detection limit is 0.33 mmol·L^-1 (at 3σ). As for H₂O₂, the reduction current at -0.033 V (vs. Ag/AgCl) is linear in the concentration range from 4.0 to 35.0 mmol·L^-1 and the detection limit is 1.3 mmol·L^-1 (at 3σ). The real sample was analyzed with satisfactory results, which indicated that BPE had potential applications in the field of electrochemical biosensor. Graphical abstract Photos of (a) black phosphorene (BPE) solution, (b) poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonate) (PEDOT:PSS), (c) BPE-PEDOT:PSS (1:5) dispersion, and the fabrication procedure of this electrochemical sensor. It was applied to the determination of trichloroacetic acid, nitrite and hydrogen peroxide.

Electrocatalytic studies on imidazolium based ionic liquids: defining experimental conditions

The number of publications devoted to studying electrochemical reactions in room temperature ionic liquids (RTILs) is constantly growing, but very few of them have been devoted to defining proper experimental conditions to obtain reproducible electrochemical results. In this work, we demonstrate that the combination of a proper RTIL purification treatment and a filtered Ar gas stream allow us to obtain featureless voltammograms in [C4mim][BF4], [C4mim][NTf2], and [C4m2im][NTf2], which otherwise present signals associated with different types of impurities such as water and some minor electroactive impurities acquired during the RTIL synthesis process. Moreover, we demonstrate that bubbling Ar, or another inert gas, through the electrolyte in order to purge O2 dissolved in RTILs is one of the major sources of water and O2 impurities incorporated in RTILs within the electrochemical cell. To overcome this source of water uptake, we have incorporated a gas stream purification filter before the gas reaches the RTIL in the electrochemical cell. To illustrate the effect of these impurities in relevant electrocatalytic studies, we study the electrocatalytic reduction of CO2 on Pt nanoparticles and the key role of an appropiate filter when the CO2 gas stream is bubbled within imidazolium based RTILs. Our cyclic voltammetric studies point out that CO2 electroreduction on Pt nanoparticles only presents activity in [C4mim][NTf2] and [C4m2im][NTf2], thus suggesting that the C-2 position on the imidazolium ring is not the key position in CO2 electrochemical reduction. In contrast, the same Pt nanoparticles are inactive towards CO2 electroreduction in [C4mim][BF4], which is a more hydrophilic RTIL.

A voltammetric biosensor based on poly(o-methoxyaniline)-gold nanocomposite modified electrode for the simultaneous determination of dopamine and folic acid

Dopamine (DA) and Folic acid (FA) are co-existing compounds in biological fluids that plays a vital role in central nervous system and human metabolism. DA is an important neurotransmitter in the brain's neural circuits and its diminution often results in Parkinson's disease. Folate is another form of folic acid, which is known as one of the B vitamins. It is utilized as an additive by women during pregnancy in order to prevent the neural tube defects. The present study reports on the fabrication of electrochemical sensor for the simultaneous determination of DA and FA using poly(o-methoxyaniline)-gold (POMA-Au) nanocomposite. The POMA-Au nanocomposite was prepared via insitu chemical oxidative polymerization method and characterized using X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM) and X-ray photoelectron spectroscopy (XPS). The suitability of POMA-Au nanocomposite as a modifier for the electrocatalytic detection of DA and FA in aqueous solution was investigated by cyclic voltammetry (CV), differential pulse voltammetry (DPV) and chronoamperometry (CA) techniques. The fabricated POMA-Au/GCE sensor exhibited sharp and intense peaks towards the electro-oxidation of DA and FA as compared to bare electrode. The sensor exhibited the promising electron mediating behavior with well separated oxidation peaks with a potential difference of about 350.0 mV. The linear calibration plots of DA and FA were obtained from 10.0 to 300.0 μM and 0.5 to 900.0 μM with the detection limits of 0.062 μM and 0.090 μM, respectively. The reliability of this sensor was verified to be precise as well as sensitive for the determination of DA and FA in pharmaceutical samples and human urine samples.

Electrochemical determination of folic acid: A short review

Folic acid (FA) is an electroactive compound of biological origin. It helps our body to produce and maintain healthy cells. It can significantly reduce the occurrence of neural tube defects and also prevents change in DNA structure. FA deficiency can lead to various health risks. Therefore, a sensitive, specific, and reproducible way of FA detection is essential. A number of analytical methods are in practice for the quantification of FA. However, electroanalytical methods are attracting much attention because of their advantage over conventional methods, as they are fast, simple, sensitive, and cost effective. Moreover, modification of electrodes offers control over size and morphology which allows miniaturization for applicability in portable electrochemical devices.

Graphene-Gold Nanoparticles Hybrid-Synthesis, Functionalization, and Application in a Electrochemical and Surface-Enhanced Raman Scattering Biosensor

Graphene is a single-atom-thick two-dimensional carbon nanosheet with outstanding chemical, electrical, material, optical, and physical properties due to its large surface area, high electron mobility, thermal conductivity, and stability. These extraordinary features of graphene make it a key component for different applications in the biosensing and imaging arena. However, the use of graphene alone is correlated with certain limitations, such as irreversible self-agglomerations, less colloidal stability, poor reliability/repeatability, and non-specificity. The addition of gold nanostructures (AuNS) with graphene produces the graphene-AuNS hybrid nanocomposite which minimizes the limitations as well as providing additional synergistic properties, that is, higher effective surface area, catalytic activity, electrical conductivity, water solubility, and biocompatibility. This review focuses on the fundamental features of graphene, the multidimensional synthesis, and multipurpose applications of graphene-Au nanocomposites. The paper highlights the graphene-gold nanoparticle (AuNP) as the platform substrate for the fabrication of electrochemical and surface-enhanced Raman scattering (SERS)-based biosensors in diverse applications as well as SERS-directed bio-imaging, which is considered as an emerging sector for monitoring stem cell differentiation, and detection and treatment of cancer.