A very low potential electrochemical detection of l-cysteine based on a glassy carbon electrode modified with multi-walled carbon nanotubes/gold nanorods

Highly dispersed Cu and Ni nano cluster sensor for ultrasensitive electrochemical detection of antiviral drug lamivudine

The accurate and rapid detection for the nucleoside reverse transcriptase inhibitor lamivudine (LAM, 3TC) in cellular systems is always a challenge in the clinic application. Here, a sensitive Cu and Ni nano cluster sensor for LAM is generated under hydrothermal conditions.The Cu and Ni atoms are highly dispersed and aggregated in the nanosized opening pore windows of the synthesized LTA zeolite, through the diatomic synergistic contribution of Cu and Ni and the enrichment of zeolitic channel pores. Using differential pulse voltammetry (DPV), the detection limit (LOD) of LAM at the potential (- 0.15 V) can reach 0.001 pM and the linear range is 0.002 pM-0.002 μM. Since the nano cluster is separated and restricted by the nanosized windows of the zeolite framework, the sensor provides high stability, good recovery (92.5-109%) and RSD (0.8-3.2%) in the analysis of tap water, RPMI 1640 medium, and rabbit serum. The Cu/Ni/LTA zeolite-modified glassy carbon electrode (Cu/Ni/LTA/GCE) exhibits excellent catalytic performance for LAM with high selectivity over potentially interfering agents. A sensitive Cu and Ni nano cluster sensor for LAM is generated in the hydrothermal condition that the Cu and Ni atoms are highly dispersed and aggregated in the nanosized opening pore windows of the as-synthesized LTA zeolite. Through the diatomic synergistic contribution of Cu and Ni and the enrichment of zeolitic channel pores, the observed limit of detection (LOD) can reach 0.001 pM under differential pulse voltammetry (DPV) method with a wide linear relationship to 0.002 μM.

Electropotential-Inspired Star-Shaped Gold Nanoconfined Multiwalled Carbon Nanotubes: A Proof-of-Concept Electrosensoring Interface for Lung Metastasis Biomarkers

Herein, an innovative way of designing a star-shaped gold nanoconfined multiwalled carbon nanotube-engineered sensoring interface (AuNS@MWCNT//GCE) is demonstrated for quantification of methionine (MTH); a proof of concept for lung metastasis. The customization of the AuNS@MWCNT is assisted by surface electrochemistry and thoroughly discussed using state-of-the-art analytical advances. Micrograph analysis proves the protrusion of nanotips on the surface of potentiostatically synthesized AuNPs and validates the hypothesis of Turkevich seed (AuNP)-mediated formation of AuNSs. In addition, a facile synthesis of electropotential-assisted transformation of MWCNTs to luminescent nitrogen-doped graphene quantum dots (N_d-GQDs avg. ∼4.3 nm) is unveiled. The sensor elucidates two dynamic responses as a function of C_MTH ranging from 2 to 250 μM and from 250 to 3000 μM with a detection limit (DL) of ∼0.20 μM, and is robust to interferents except for tiny response of a similar -SH group bearing Cys (<9.00%). The high sensitivity (0.44 μA·μM^-1·cm^-2) and selectivity of the sensor can be attributed to the strong hybridization of the Au nanoparticle with the sp² C atom of the MWCNTs, which makes them a powerful electron acceptor for Au-SH-MTH interaction as evidenced by density functional theory (DFT) calculations. The validation of the acceptable recovery of MTH in real serum and pharma samples by standard McCarthy-Sullivan assay reveals the holding of great promise to provide valuable information for early diagnosis as well as assessing the therapeutic consequence of lung metastasis.

Controllable synthesis of BiPr composite oxide nanowires electrocatalyst for sensitive L-cysteine sensing properties

BiPr composite oxide nanowires with rhombodedral Bi_1.35Pr_0.65O₃, monoclinic Bi₂O₃and monoclinic Pr₅O₉phases were synthesized via a facile sodium dodecyl sulfate (SDS) assisted hydrothermal route. The obtained nanowires were characterized by x-ray diffraction, electron microscopy, x-ray photoelectron spectroscopy and electrochemical measurements. The BiPr composite oxide nanowires possess poly-crystalline structure, semi-circular tips, diameter and length of 20-100 nm and several micrometers, respectively. SDS is essential for the formation of the BiPr composite oxide nanowires which can be explained by a SDS assisted hydrothermal growth process. Electrochemical impedance spectroscopy shows that the electrons are easier to transfer by the surface of the BiPr composite oxide nanowires modified glassy carbon electrode (GCE) than bare GCE. The BiPr composite oxide nanowires modified GCE possesses good electro-catalytic activity for L-cysteine detection with a pair of quasi-reversible cyclic voltammetry peaks at +0.04 V and -0.72 V for the oxidation and reduction of L-cysteine, respectively. The roles of the scan rate, electrolyte species and L-cysteine concentration on the electrochemical responses of L-cysteine at the nanowires modified GCE were systematically analyzed. The BiPr composite oxide nanowires modified GCE presents a linear response range from 0.001 to 2 mM and detection limit of 0.27μM, good reproducibility and stability.

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.

Syntheses of Water-Soluble Silver(II)-Phthalocyanines toward Optical Sensing for Thiol Detection

Water-soluble silver(II)-phthalocyanine complexes (AgPcs), tetrakis{4-(N-alkylpyridinium)thio}phthalocyaninato silver(II) tetrafluoroborate, [Ag(tRpySpc)](BF₄)₄, (R = Me and Et), have been synthesized for the first time by quaternization of pyridyl groups of tetrakis(4-pyridylthio)phthalocyaninato silver(II) by using Meerwein reagents and characterized by ESI-MS, elemental analyses, and optical absorption spectroscopy. Although they strongly aggregate in water, the presence of appropriate surfactants, such as polyethyleneglycol-monooleyl ether (n = approximately 50; PEG50) and sodium dodecyl sulfate, effectively disaggregates them to monomeric species. The spectral properties of the AgPcs and their aggregates in aqueous and nonaqueous solutions have been investigated by optical absorption, emission, and magnetic circular dichroism spectroscopy. These AgPcs rapidly react with thiols such as cysteine, glutathione, homocysteine, and sodium 2-sulfanylethanesulfonate (even on the order of 0.01 mM) in aqueous PEG50 solutions at room temperature to liberate the corresponding macrocyclic ligand, H₂Pc, but not with the other amino-acid analogs without sulfhydryl groups. The molar ratio of thiol to AgPc has been determined to be 1:1. Since AgPcs are essentially nonfluorescent at room temperature, while H₂Pcs emit intense red fluorescence, AgPcs can be a potent thiol-sensor toward bioimaging.

Voltammetric Determination of Cysteine (2-amino-3-mercaptopropanoic acid, CySH) by Means of 4,4'-biphenol as a Homogeneous Mediator

In the present research, 4,4′-biphenol was used as a homogeneous mediator for determining cysteine (CySH) on a Glassy Carbon Electrode (GCE). To describe the electrochemical properties of 4,4′-biphenol and to examine its electrocatalytic impacts on cysteine oxidation, both Cyclic Voltammetry (CV) and Linear Sweep Voltammetry (LSV) were employed. Our findings revealed that 4,4′-biphenol could significantly accelerate the reactions related to electron transfer to CySH. Moreover, the diffusion coefficient of CySH and its reaction with the catalytic constant of 4,4′-diphenoquinone was estimated via chronoamperometry technique. The results showed that cysteine concentration range of 10-1000 μM led to linear increases in the oxidation peaks, thus to providing a detection of 0.99 μM with R² = 0.993. A Relative Standard Deviation (RSD) of 2.5% was achieved after performing 7 cysteine replicates (100 μM), and CySH was successfully determined in real serum samples through the proposed approach.

A water-soluble dual-site fluorescent probe for the rapid detection of cysteine with high sensitivity and specificity

A water-soluble turn-on fluorescent probe has been rationally designed and synthesized to distinguish Cys from Hcy and GSH in less than five seconds. It has high sensitivity and strong anti-interference ability to other amino acids and ions. Its ultra-rapid detection of Cys in aqueous systems could be attributed to dual response sites imparted by the probe.

Novel applications of perovskite oxide via catalytic peroxymonosulfate advanced oxidation in aqueous systems for trace L-cysteine detection

Perovskite oxides offer new opportunities in wastewater treatment via catalytic oxidation. Herein, we report a new application of perovskite oxides for biological detection via catalytic decolourisation and colorimetric determination. The presence of trace biomolecules in an aqueous system would interfere the decolourisation process of dyes, where the decolourisation rate is quantitatively correlated to the biomolecular concentration. In this work, trace L-cysteine (Cys) detection was demonstrated on the basis of a Ag-Ba_0.5Sr_0.5Co_0.75Fe_0.2O_3-δ (Ag-BSCF)/peroxymonosulfate/textile dye system. Thiol-containing cysteine can bind to Ag, Co and Fe atoms, therefore shielding the catalytic performance of the perovskite in degradation of dye solutions. Such a cost-effective biosensor system presents an excellent linear response in Cys concentration ranging from nM to μM.

Advances in biotechnological synthetic applications of carbon nanostructured systems

In the last few years carbon nanostructures have been applied for the immobilization of enzymes and biomimetic organo-metallic species useful for biotechnological applications. The nature of the support and the method of immobilization are responsible for the stability, reactivity and selectivity of the system. In this review, we focus on the recent advances in the use of carbon nanostructures, carbon nanotubes, carbon nanorods, fullerene and graphene for the preparation of biocatalytic and biomimetic systems and for their application in the development of green chemical processes.

Glassy carbon electrode modified with 7,7,8,8-tetracyanoquinodimethane and graphene oxide triggered a synergistic effect: Low-potential amperometric detection of reduced glutathione

A sensitive electrochemical sensor based on the synergistic effect of 7,7,8,8-tetracyanoquinodimethane (TCNQ) and graphene oxide (GO) for low-potential amperometric detection of reduced glutathione (GSH) in pH 7.2 phosphate buffer solution (PBS) has been reported. This is the first time that the combination of GO and TCNQ have been successfully employed to construct an electrochemical sensor for the detection of glutathione. The surface of the glassy carbon electrode (GCE) was modified by a drop casting using TCNQ and GO. Cyclic voltammetric measurements showed that TCNQ and GO triggered a synergistic effect and exhibited an unexpected electrocatalytic activity towards GSH oxidation, compared to GCE modified with only GO, TCNQ or TCNQ/electrochemically reduced GO. Three oxidation waves for GSH were found at -0.05, 0.1 and 0.5V, respectively. Amperometric techniques were employed to detect GSH sensitively using a GCE modified with TCNQ/GO at -0.05V. The electrochemical sensor showed a wide linear range from 0.25 to 124.3μM and 124.3μM to 1.67mM with a limit of detection of 0.15μM. The electroanalytical sensor was successfully applied towards the detection of GSH in an eye drop solution.

Single wall carbon nanotube (SWCNT)–gold nanorod (AuNR) conjugates via thermally-mild reaction conditions

A thermally-mild method for covalent binding of SWCNTs to AuNRs, based on an inverse-electron-demand Diels–Alder reaction, is established and discussed.

Gold nanoparticles and their applications in biomedicine

Although used in medical applications for centuries, the development of nanotechnology has shed new light in the plethora of possible medical and biological applications using gold-based nanostructures. Gold nanostructures are stable and relatively inert in biological systems, leading to low reatogenicity, biocompatibility and general lack of toxicity. Allied to that, gold nanoparticles present optical and electronic properties that have been exploited in a range of biomedical applications. In this review we discuss biologically relevant properties of gold nanoparticles and how they are used in some biomedicine fields, especially those involving biosensing of biological analytes – including viruses and antibodies against them, cancer therapies, and antigen delivery, including viral antigens – as part of nonclassic vaccine strategies.

Engineered Carbon-Nanomaterial-Based Electrochemical Sensors for Biomolecules

The study of electrochemical behavior of bioactive molecules has become one of the most rapidly developing scientific fields. Biotechnology and biomedical engineering fields have a vested interest in constructing more precise and accurate voltammetric/amperometric biosensors. One rapidly growing area of biosensor design involves incorporation of carbon-based nanomaterials in working electrodes, such as one-dimensional carbon nanotubes, two-dimensional graphene, and graphene oxide. In this review article, we give a brief overview describing the voltammetric techniques and how these techniques are applied in biosensing, as well as the details surrounding important biosensing concepts of sensitivity and limits of detection. Building on these important concepts, we show how the sensitivity and limit of detection can be tuned by including carbon-based nanomaterials in the fabrication of biosensors. The sensing of biomolecules including glucose, dopamine, proteins, enzymes, uric acid, DNA, RNA, and H2O2 traditionally employs enzymes in detection; however, these enzymes denature easily, and as such, enzymeless methods are highly desired. Here we draw an important distinction between enzymeless and enzyme-containing carbon-nanomaterial-based biosensors. The review ends with an outlook of future concepts that can be employed in biosensor fabrication, as well as limitations of already proposed materials and how such sensing can be enhanced. As such, this review can act as a roadmap to guide researchers toward concepts that can be employed in the design of next generation biosensors, while also highlighting the current advancements in the field.

A novel cysteine sensor based on modification of carbon paste electrode by Fe(II)-exchanged zeolite X nanoparticles

An electrochemical sensor based on carbon paste electrode (CPE) modified with iron(II) doped into a synthesized nano-particles of zeolite X (Fe(II)-NX/ZCME) was constructed, which is highly sensitive for detection of cysteine (Cys). The modified electrode showed an excellent electro-activity for oxidation of Cys in phosphate buffer at pH7.4. It has been found that anodic peak potential of Cys oxidation, compared with the unmodified CPE (UCPE), was shifted towards negative values at the surface of the modified electrode under the optimum condition. The peak current increased linearly with the Cys concentration in the wide range of 5.0 × 10(-9)-3.0 × 10(-3) mol L(-1). The very low detection limit was obtained to be 1.5 × 10(-10) mol L(-1). Finally, the modified electrode was used as a selective, simple and precise new electrochemical sensor for the determination of Cys in the real samples, such as pharmaceutical and biological fluids.

Simple and facile preparation of silver–polydopamine (Ag–PDA) core–shell nanoparticles for selective electrochemical detection of cysteine

A simple one-step method for the preparation of silver–polydopamine (Ag–PDA) core–shell nanoparticles is proposed and its application for non-enzymatic electrochemical detection of cysteine is demonstrated.

Synthesis of dendritic silver nanostructures supported by graphene nanosheets and its application for highly sensitive detection of diazepam

In this paper, preparation, characterization and application of a new sensor for fast and simple determination of trace amount of diazepam were described. This sensor is based on Ag nanodendrimers (AgNDs) supported by graphene nanosheets modified glassy carbon electrode (GNs/GCE). The AgNDs were directly electrodeposited on the surface of electrode via potentiostatic method without using any templates, surfactants, or stabilizers. The structure of the synthesized AgNDs/GNs was characterized by scanning electron microscopy (SEM), energy dispersive X-ray (EDX) analysis, X-ray diffraction (XRD) and electrochemical impedance spectroscopy (EIS) techniques. The nanodendrimers with tree-like and hierarchical structures have a fascinating structure for fabrication of effective electrocatalysts. The experimental results confirmed that AgNDs/GNs/GC electrode has good electrocatalytic activity toward the reduction of diazepam. A low detection limit of 8.56 × 10^− 8 M and a wide linear detection range of 1.0 × 10^− 7 to 1.0 × 10^− 6 M and 1.0 × 10^− 6 to 20 × 10^− 6 M were achieved via differential pulse voltammetry (DPV). The proposed electrode displayed excellent repeatability and long-term stability and it was satisfactorily used for determination of diazepam in real samples (commercially tablet, injection and human blood plasma) with high recovery.

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Applying a simple, fast and cost-effective method for synthesis of silver nanodendrimers

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Characterization of AgNDs/GNs/GCE surface by SEM, EDX, XRD, EIS and CV methods

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Successful application of this sensor for diazepam determination with an excellent detection limit

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Calculation of diffusion coefficient, electron transfer coefficient and standard heterogeneous rate constant for diazepam

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Satisfactorily using of this sensor for diazepam determination in several real samples

Rapid determination of furosemide in drug and blood plasma of wrestlers by a carboxyl-MWCNT sensor

A novel method is developed for the quantification of furosemide in biological fluids. The method is based on the electro-reduction of Zn(II)-furosemide complex at carboxyl-MWCNT modified glassy carbon electrode. It is shown that, in Britton-Robinson buffer (pH5.7) the reduction peak of Zn(II)-furosemide complex formed at -1.0 V (versus, Ag/AgCl). The increment of current signal obtained from the reduction peak current of the Zn(II)-furosemide complex was rectilinear with furosemide concentration in the range of 0.03 to 140.0 μg ml(-1), with a detection limit of 0.007 μg ml(-1). The drug recovery ranged between 97.8% and 100.8% and the mean drug recovery was 98.89%. The accuracies (relative error% and RSD%) were less than 15% and are acceptable according to the US FDA guideline for bioanalytical method validation. The sensor was used for quantification of furosemide in drug and biological fluid samples. The data of drug analysis were compared with the standard method.