Gold nanoparticles embedded electropolymerized thin film of pyrimidine derivative on glassy carbon electrode for highly sensitive detection of l -cysteine

Trace identification of cysteine enantiomers based on an electrochemical sensor assembled from CuxS@SOD zeolite

The nonchiral sensor concept based on a sodalite (SOD) zeolite loaded CuxS (CuxS@SOD) catalyst is proposed as a sensing platform for chiral cysteine (Cys) determination. Chiral Cys is analyzed by the difference of binding capacity between CuxS catalysts. The observed current in amperometric i-t curve (A i-t C) is always positive for the L-cysteine (L-Cys), while it is negative for the D-cysteine (D-Cys). Under differential pulse voltammetry (DPV) method, the characteristic current peak for the CuxS@SOD moves to right (positive potential position) with the addition of L-Cys while it moves to left (negative potential direction) with the addition of D-Cys, respectively. Cyclic voltammetry (CV) is consistent with DPV and discusses the diffusion control mechanism. In this work, the ultra-trace determination of cysteine enantiomers reaches the limit of detection (LOD) of 0.70 fM and 0.60 fM by the highly efficient CuxS catalyst restrained in the nanosized SOD zeolite cages of the opening window pores, respectively. The sensor opens up a novel potential prospect for achiral composite in the field of chiral recognition through electrochemical methods with extra-low concentration.

Nanomaterial-based electrochemical sensors for detection of amino acids

Amino acids are the building blocks of proteins and muscle tissue. They also play a significant role in physiological processes related to energy, recovery, mood, muscle and brain function, fat burning and stimulating growth hormone or insulin secretion. Accurate determination of amino acids in biological fluids is necessary because any changes in their normal ranges in the body warn diseases like kidney disease, liver disease, type 2 diabetes and cancer. To date, many methods such as liquid chromatography, fluorescence mass spectrometry, etc. have been used for the determination of amino acids. Compared with the above techniques, electrochemical systems using modified electrodes offer a rapid, accurate, cheap, real-time analytical path through simple operations with high selectivity and sensitivity. Nanomaterials have found many interests to create smart electrochemical sensors in different application fields e.g. biomedical, environmental, and food analysis because of their exceptional properties. This review summarizes recent advances in the development of nanomaterial-based electrochemical sensors in 2017-2022 for the detection of amino acids in various matrices such as serum, urine, blood and pharmaceuticals.

Development of L-cysteine sensor based on thallium oxide coupled multi-walled carbon nanotube nanocomposites with electrochemical approach

Here, Nanocomposites of thallium oxide doped multi-walled carbon nanotube (Tl2O.MWCNT NCs) were prepared by utilizing the wet-chemical method (WCM) in an alkaline phase at low temperature. Different optical procedures (FTIR: Fourier Transform Infra-Red Spectroscopy, XRD: Powder X-ray diffraction, FESEM: Field-Emission Scanning Electron Microscopy, XEDS: X-ray Electron Dispersive Spectroscopy, TEM: Tunneling Electron Microscopy, and XPS: X-ray photoelectron spectroscopy) were used to fully characterize (Optical, structural, crystalline, morphological, and elemental etc.) of the prepared Tl2O.MWCNT NCs. Modification of the thin-layer with NCs onto glassy carbon electrode (GCE) is prepared and applied for the enzyme-free detection of selective and sensitive L-cysteine by electrochemical approach. Using a reliable current-voltage approach, analytical sensing indexes such as sensitivity, LDR, LOD, LOQ, durability, and interference were assessed by fabricated sensor probe (GCE/Tl2O.MWCNT NCs/CPM) in selective detection of L-cysteine in a room condition, whereas nafion was used as conducting polymer matrix (CPM) during the fabrication of GCE with NCs. L-cysteine calibration plot was found to be linear over an extensive range of concentration. The calibration curve was used to calculate the sensing parameters such as sensitivity (316.46 pAμM-1cm-2), LOD down to (~18.90 ± 1.89 pM), and LOQ (63.0 pM) of the prepared sensor. The use of a simple WCM to validate the Tl2O.MWCNT NCs is a good approach for developing a NCs-based sensor for enzyme-free biomolecule identification and detection in the biomedical and health care fields in a broad scale. This proposed sensor (GCE/Tl2O.MWCNT NCs/CPM) is used to detect selective L-cysteine in real biological samples such as human, mouse, and rabbit serum and found acceptable and satisfactory results.

Electrochemical Amino Acid Sensing: A Review on Challenges and Achievements

The rapid growth of research in electrochemistry in the last decade has resulted in a significant advancement in exploiting electrochemical strategies for assessing biological substances. Among these, amino acids are of utmost interest due to their key role in human health. Indeed, an unbalanced amino acid level is the origin of several metabolic and genetic diseases, which has led to a great need for effective and reliable evaluation methods. This review is an effort to summarize and present both challenges and achievements in electrochemical amino acid sensing from the last decade (from 2010 onwards) to show where limitations and advantages stem from. In this review, we place special emphasis on five well-known electroactive amino acids, namely cysteine, tyrosine, tryptophan, methionine and histidine. The recent research and achievements in this area and significant performance metrics of the proposed electrochemical sensors, including the limit of detection, sensitivity, stability, linear dynamic range(s) and applicability in real sample analysis, are summarized and presented in separate sections. More than 400 recent scientific studies were included in this review to portray a rich set of ideas and exemplify the capabilities of the electrochemical strategies to detect these essential biomolecules at trace and even ultra-trace levels. Finally, we discuss, in the last section, the remaining issues and the opportunities to push the boundaries of our knowledge in amino acid electrochemistry even further.

Effect of Supporting Background Electrolytes on the Nanostructure Morphologies and Electrochemical Behaviors of Electrodeposited Gold Nanoparticles on Glassy Carbon Electrode Surfaces

Electrodeposition is an electrochemical method employed to deposit stable and robust gold nanoparticles (AuNPs) on electrode surfaces for creating chemically modified electrodes (CMEs). The use of several electrodeposition techniques with different experimental parameters allow in obtaining various surface morphologies of AuNPs deposited on the electrode surface. By considering the electrodeposition of AuNPs in various background electrolytes could play an important strategy in finding the most suitable formation of the electrodeposited AuNP films on the electrode surface. This is because different electrode roughnesses can have different effects on the electrochemical activities of the modified electrodes. Thus, in this study, the electrodeposition of AuNPs onto the glassy carbon (GC) electrode surfaces in various aqueous neutral and acidic electrolytes was achieved by using the cyclic voltammetry (CV) technique with no adjustable CV parameters. Then, surface morphologies and electrochemical activities of the electrodeposited AuNPs were investigated using scanning electron microscopy (SEM), atomic force microscopy (AFM), CV, and electrochemical impedance spectroscopy (EIS). The obtained SEM and 3D-AFM images show that AuNPs deposited at the GC electrode prepared in NaNO₃ solution form a significantly better, uniform, and homogeneous electrodeposited AuNP film on the GC electrode surface with nanoparticle sizes ranging from ∼36 to 60 nm. Meanwhile, from the electrochemical performances of the AuNP-modified GC electrodes, characterized by using a mixture of ferricyanide and ferrocyanide ions [Fe(CN₆)^3-/4-], there is no significant difference observed in the case of charge-transfer resistances (R _ct) and heterogeneous electron-transfer rate constants (k ^o), although there are differences in the surface morphologies of the electrodeposited AuNP films. Remarkably, the R _ct values of the AuNP-modified GC electrodes are lower than those of the bare GC electrode by 18-fold, as the R _ct values were found to be ∼6 Ω (p < 0.001, n = 3). This has resulted in obtaining k ^o values of AuNP-modified GC electrodes between the magnitude of 10^-2 and 10^-3 cm s^-1, giving a faster electron-transfer rate than that of the bare GC electrode (10^-4 cm s^-1). This study confirms that using an appropriate supporting background electrolyte plays a critical role in preparing electrodeposited AuNP films. This approach could lead to nanostructures with a more densely, uniformly, and homogeneously electrodeposited AuNP film on the electrode surfaces, albeit utilizing an easy and simple preparation method.

Enticing 3D peony-like ZnGa2O4 microstructures for electrochemical detection of N, N-dimethylmethanamide chemical

We demonstrate the hydrothermal synthesis of three dimension (3D) peony-like morphology of zinc gallate (ZnGa₂O₄), dominated by assembled nanosheets and applied as electrode material in electrochemical detection of N,N-dimethylmethanamide chemical. The crystalline, structural and compositional characterizations deduced the formation of high quality ZnGa₂O₄ with spinal crystal structure. Peony-like 3D ZnGa₂O₄ was benefited by a high surface area of ~62.3 m² g^-1, good pore distribution (mean pore diameter of ~23.3 nm) and large pore volume of ~0.3622 cm³ g^-1. N,N-dimethylmethanamide chemical sensor based on peony-like 3D ZnGa₂O₄ electrode presented a linear curve in the working dynamic range of 1 nM-10 mM. Significantly improved chemical sensitivity of ~154.2 mA mM^-1 cm^-2 with low detection limit value of ~0.14 μM were achieved. The fabricated sensor based on peony-like 3D ZnGa₂O₄ electrode endorsed real sample analysis and ascertained the selectivity towards N,N-dimethylmethanamide chemical by analyzing a range of interfering analytes, viz. ethanol, tetrahydrofuran, methyl amine chemical.