A novel modified carbon paste electrode based on NiO/CNTs nanocomposite and (9, 10-dihydro-9, 10-ethanoanthracene-11, 12-dicarboximido)-4-ethylbenzene-1, 2-diol as a mediator for simultaneous determination of cysteamine, nicotinamide adenine dinucleotide and folic acid

Silver nanoparticles modified with MoS2 and β-cyclodextrin as SERS substrate for rapid determination of cysteamine hydrochloride in meat products

An efficient Surface-enhanced Raman scattering (SERS) method for the detection of cysteamine hydrochloride (CSH) was developed by synthesizing a composite substrate comprising silver nanoparticles (AgNPs) functionalized with MoS2 and β-cyclodextrin (β-CD). The enhanced Raman signals of CSH by β-CD/MoS2/AgNPs substrate were the contribution of electromagnetic enhancement (EM) as well as chemical enhancement (CM), and the enhancement factor (EF) can reach up to 3.11 × 106 (peak at 633 cm-1). Various instrumental techniques were used to characterize the substrate, such as X-ray diffraction (XRD), thermogravimetric analysis (TGA), transmission electron microscopy (TEM), high-angle annular dark field scanning transmission electron microscopy (HAADF-STEM) and ultraviolet visible (UV-vis). The binding of β-CD/MoS2/AgNPs and CSH was confirmed by UV-vis and Fourier transform infrared (FT-IR). The optimal experimental conditions were determined by single factor experiments as well as response surface model. The influences of different metal ions and analogous drugs on the detection of CSH were investigated. Under optimum conditions, a good linear correlation (R = 0.9997) was established for CSH in the range of 10.00-1000.00 nmol/L, and the limit of detection (LOD) was as low as 0.78 nmol/L (S/N = 3). The contents of CSH in meat samples were detected. The recovery was 96.6-103.1 %, and the relative standard deviation (RSD) of the measurement was 0.7-3.9 % (n = 7).

Unveiling thiol biomarkers: Glutathione and cysteamine

The physiological and clinical importance of Glutathione and Cysteamine is emphasized by their participation in a range of conditions, such as diabetes, cancer, renal failure, Parkinson's disease, and hypothyroidism. This necessitates the requirement for accessible, expedited, and cost-efficient testing that can facilitate clinical diagnosis and treatment options. This article examines numerous techniques used to detect both glutathione and cysteamine. The discussed methods include electroanalytical techniques such as voltammetry and amperometry, which are examined for their sensitivity and ability to provide real-time analysis. Furthermore, this study investigates the accuracy of gas chromatography-mass spectrometry (GC-MS) and high-performance liquid chromatography (HPLC) in measuring the concentrations of glutathione and cysteamine. Additionally, the potential of new nanotechnology-based methods, such as plasmonic nanoparticles and quantum dots, to improve the sensitivity of detecting glutathione and cysteamine is emphasized.

Microalgae derived honeycomb structured mesoporous diatom biosilica for adsorption of malachite green: Process optimization and modeling

The present study investigated the removal of malachite green dye from aquifers by means of microalgae-derived mesoporous diatom biosilica. The various process variables (dye concentration, pH, and adsorbent dose) influencing the removal of the dye were optimized and their interactive effects on the removal efficiency were explored by response surface methodology. The pH of the solution (pH = 5.26) was found to be the most dominating among other tested variables. The Langmuir isotherm (R2 = 0.995) best fitted the equilibrium adsorption data with an adsorption capacity of 40.7 mg/g at 323 K and pseudo-second-order model (R2 = 0.983) best elucidated the rate of dye removal (10.6 mg/g). The underlying mechanism of adsorption was investigated by Weber-Morris and Boyd models and results revealed that the film diffusion governed the overall adsorption process. The theoretical investigations on the dye structure using DFT-based chemical reactivity descriptors indicated that malachite green cations are electrophilic, reactive and possess the ability to accept electrons, and are strongly adsorbed on the surface of diatom biosilica. Also, the Fukui function analysis proposed the favorable adsorption sites available on the adsorbent surface.

A new peroxyoxalate chemiluminescence of bis (2, 4-dinitrophenyl) oxalate (DNPO) using pyronin Y as the fluorophore and its application to the flow-based determination of cysteamine

Peroxyoxalate chemiluminescence (POCL) systems have received great attention due to their high quantum yield and the ability to emit a wide-range colors by the utilizing different fluorophores. In this research, Pyronin Y (PY) was first introduced as the fluorophore for a POCL system. Our results indicated that the reaction of (2, 4-dinitroophenyl) oxalate (DNPO) with hydrogen peroxide (H₂O₂) catalyzed by sodium salicylate (SS) could transfer energy to Pyronin Y via the formation of the dioxetanedione intermediate and emit orange-red light. The relationships between chemiluminescence (CL) intensity and the concentrations of DNPO, fluorophore, H₂O₂, and the catalyst were investigated. Moreover, the analytical utilization of the new CL system was evaluated by detecting a drug, cysteamine, in pharmaceuticals. A linear working range for cysteamine concentrations from 3 × 10 ^-8 to 7.5 × 10 ^-6 molL^-1 (r > 0.9907, n = 5) and a detection limit of 7.8 × 10^-9 molL^-1 were obtained, respectively. The relative standard deviation for five repetitive determinations was less than 3.8 %, with estimated recoveries of 100.1 % and 103.4 %. This method shows high sensitivity for the assay of cysteamine.

Mechanism of time-dependent toxicity of quinolone antibiotics on luminescent bacteria Vibrio qinghaiensis sp.-Q67

Four quinolone antibiotics (ciprofloxacin (CIP), enrofloxacin (ENR), sparfloxacin (SPA), gatifloxacin (GAT)) and their binary mixtures at environmentally relevant concentrations exhibited time-dependent hormesis on Vibrio qinghaiensis sp.-Q67 (Q67). The study aims to investigate the time-dependent toxicity of low-dose pollutants and the occurrence of hormesis. These indicators, total protein (TP), reactive oxygen species (ROS), superoxide dismutase (SOD), catalase (CAT), malondialdehyde (MDA) and luminescence-related chemicals flavin mononucleotide (FMN), nicotinamide adenine dinucleotide (NADH), were measured to explore the mechanism of hormesis. The results showed a trend of increases in all indicators after 12 h of exposure, reaching maximal effects at 60 h and then decreasing as time progressed. At 36 h, 60 h and 84 h, the results showed a gradual increase followed by a decreasing trend in TP, FMN and NADH as the concentration in the group increased, whereas ROS, CAT, SOD and MDA showed the opposite trend. Notably, the degree of changes was related to the magnitude of hormesis. At low concentrations, the content of ROS and MDA decreased, the activity of CAT and SOD was lower, but the content of TP, FMN, NADH gradually increased, positively correlated with the promotion of Q67. At high concentrations, ROS and MDA content in Q67 increased, triggering the antioxidant defense mechanism (CAT and SOD activity increased), but TP, FMN, NADH content decreased, negatively correlated with the inhibited Q67. Therefore, our findings demonstrated two common patterns in these seven biochemical indicators on Q67. These findings have important practical implications for the ecological risk assessment of antibiotics in aquatic environment.

A caffeic acid electrochemical sensor amplified with GNR/CoFe2O4@NiO and 1-Ethyl-3-methylimidazolium acetate; a new perspective for food analysis

Determining Caffeic acid is important as an antioxidant compound in food. In this study, caffeic acid (CA) was measured using a carbon paste electrode modified with GNR/CoFe₂O₄@NiO and 1-Ethyl-3-methylimidazolium acetate (EMIM Ac) as ion liquid. A simple sensor showed a higher current than a bare carbon paste; thus, it can be said that the modified electrode has a higher sensitivity for detecting CA. The linear range of this sensor and its detection limit was equal to 0.01-100.0 μM and 0.01 μM, respectively. Moreover, the developed electrode indicated outstanding selectivity in the presence of several interferences, high sensitivity, reproducibility, and long-term stability. The percentage recovery of CA obtained with the developed sensor affirmed its reliability for CA determination in real samples. The modified sensor's accuracy was confirmed to identify this analyte according to the results.

Glucose nano biosensor with non-enzymatic excellent sensitivity prepared with nickel-cobalt nanocomposites on f-MWCNT

NiCo (Nickel-cobalt) nanoparticles were obtained by the chemical reduction method on functionalized multi-walled carbon nanotubes. After this process, chronoamperometry, cyclic voltammetry, and amperometric methods were used to investigate the electrochemical and electrocatalytic behavior of NiCo@f-MWCNT against glucose oxidation. In addition, the NiCo@f-MWCNT nanocomposites were analyzed by characterization techniques such as X-Ray Diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Transmission Electron Microscopy (TEM), and Atomic Force Microscopy (AFM) in terms of the morphological and atomic structure of prepared nanomaterials. The sensitivity and limit of detection the non-enzymatic glucose sensor (NiCo@f-MWCNT) were calculated as 10,015 μA/mM^-1 cm^-2 0.26 μM, respectively. As a result of these studies and experiments, the NiCo@f-MWCNT nanocomposite is a really good sensor and their stability showed that the current nanomaterials expressed to be new material for the electrochemical detection of glucose.

Highly sensitive voltammetric determination of NADH based on N-CQDs decorated SnO2/ionic liquid/carbon paste electrode

A highly sensitive and selective modified electrode was successfully developed for the monitoring of nicotinamide adenine dinucleotide (NADH) in the presence of folic acid. In this regard, a carbon paste electrode (CPE) was functionalized by the nitrogen-doped carbon quantum dots/tin oxide (N-CQDs/SnO₂) nanocomposite and 1-butyl-2,3-dimethyl imidazolium hexafluorophosphate ([C₄DMIM][PF₆]) ionic liquid (IL). The structure and surface morphology of the nanocomposite were characterized by various methods, including field emission scanning electron microscopy, energy dispersive spectroscopy (EDS), high-resolution transmission electron microscopy (HR-TEM), and x-ray diffraction (XRD). The modified electrode displayed powerful and long-lasting electron mediating activity, with well-separated NADH and folic acid oxidation peaks. The sensing response of the developed [C₄DMIM][PF₆]/N-CQDs/SnO₂/CPE platform was evaluated by determining NADH via the voltammetric technique under the optimized operating conditions. The current peaks of the square wave voltammograms of NADH and folic acid increased linearly with enhancing its concentrations within the ranges of 0.003-275μM NADH and 0.4-380μM folic acid. The detection limits for NADH and folic acid were obtained at 0.8 nM and 0.1μM, respectively. Interference species such as glucose, urea, tryptophan, glycine, methionine, and vitamin B₁₂had no influence on the ability of the fabricated modified electrode to detect the target species. The low detection limit, high sensitivity, excellent selectivity, superior stability, and cost-effectiveness made it suitable for the quantification of NADH in the real biological samples with the recovery percent values in the range of 97.5%-103%.

Recent Advantages of Mediator Based Chemically Modified Electrodes; Powerful Approach in Electroanalytical Chemistry

Background:

Modified electrodes have advanced from the initial studies aimed at understanding electron transfer in films to applications in areas such as energy production and analytical chemistry. This review emphasizes the major classes of modified electrodes with mediators that are being explored for improving analytical methodology. Chemically modified electrodes (CMEs) have been widely used to counter the problems of poor sensitivity and selectivity faced in bare electrodes. We have briefly reviewed the organometallic and organic mediators that have been extensively employed to engineer adapted electrode surfaces for the detection of different compounds. Also, the characteristics of the materials that improve the electrocatalytic activity of the modified surfaces are discussed.

Objective:

Improvement and promotion of pragmatic CMEs have generated a diversity of novel and probable strong detection prospects for electroanalysis. While the capability of handling the chemical nature of the electrode/solution interface accurately and creatively increases , it is predictable that different mediators-based CMEs could be developed with electrocatalytic activity and completely new applications be advanced.

Graphenoxide Cross-Linker Based Potentiometric Biosensor Design For Sarcosine Determination

BACKGROUND

Sarcosine, also known as N-methyl glycine, is a natural amino acid that is an intermediate and by product in glycine synthesis and degradation. Recently found in many peptides, sarcosine has been researched as a newly accepted prostate cancer marker. The increased concentration of sarcosine in blood serum and the urine showed that malignancy of measured prostate cancer cells is active.

OBJECTIVE

In this article, we aimed to design a potentiometric biosensor for detection of sarcosine with a low detection limit, high selectivity, short response time, wide linear range, and satisfactory long-term stability.

METHODS

In this article, we developed a new Graphene oxide (GFOX) photosensitive cross- linker based potentiometric biosensor based on the AmiNoAcid (monomer) Decorated and Light Underpinning Conjugation Approach (ANADOLUCA) method. The functional groups determined using Raman, FT-IR, XPS analyzes, and surface characterization, the morphology of synthesized GFOX photosensitive cross-linker were determined by TEM and AFM studies. Then, the performance of the GFOX based potentiometric biosensor has been evaluated.

RESULTS

When the usage of the developed GFOX doped potentiometric biosensor against sarcosine determination, it was found that 10 -4 mM sarcosine was determined in 60 seconds in the solution. In addition, the detection limit of the GFOX doped potentiometric biosensor was found to be 9.45x10 -7 mM, and the linear potentiometric biosensor was found to be in the concentration range of 10 -1 to 10 -5 mM. The selectivity studies of the developed potentiometric biosensor were investigated using glycine solutions, and it was determined that GFOX doped potentiometric biosensor was more selective against sarcosine. Besides this, a reusability test using 10 -3 mM sarcosine solution showed that reproducible studies were performed without the loss of potential of designed potentiometric biosensor and no loss of sensitivity.

CONCLUSION

After applying the framework, we get a new potentiometric biosensor for sarcosine determination. GFOX photosensitive cross-linker was used in designing potentiometric biosensors, and this increased the stability and efficiency of the biosensor. Therefore, the developed potentiometric biosensor for sarcosine determination could be easily used for the early diagnosis of prostate cancer.

Electro-catalytic amplified sensor for determination of N-acetylcysteine in the presence of theophylline confirmed by experimental coupled theoretical investigation

The 1,l/-bis(2-phenylethan-1-ol)ferrocene, 1-butyl-3-methylimidazolium hexafluoro phosphate (BMPF6) and NiO-SWCNTs were used to modify carbon paste electrode (BPOFc/BMPF6/NiO-SWCNTs/CPE), which could act as an electro-catalytic tool for the analysis of N-acetylcysteine in this work. The BPOFc/BMPF6/NiO-SWCNTs/CPE with high electrical conductivity showed two completely separate signals with oxidation potentials of 432 and 970 mV for the first time that is sufficient for the determination of N-acetylcysteine in the presence of theophylline. The BPOFc/BMPF6/NiO-SWCNTs/CPE showed linear dynamic ranges of 0.02–300.0 μM and 1.0–350.0 μM with the detection limit of ~ 8.0 nM and 0.6 μM for the measurement of N-acetylcysteine and theophylline, respectively. In the second part, understanding the nature of interaction, quantum conductance modulation, electronic properties, charge density, and adsorption behavior of N-acetylcysteine on NiO–SWCNTs surface from first-principle studies through the use of theoretical investigation is vital for designing high-performance sensor materials. The N-acetylcysteine molecule was chemisorbed on the NiO–SWCNTs surface by suitable adsorption energies (− 1.102 to − 5.042 eV) and reasonable charge transfer between N-acetylcysteine and NiO–SWCNTs.

A sensitive "off-on" carbon dots-Ag nanoparticles fluorescent probe for cysteamine detection via the inner filter effect

In this study, we describe the construction of an "off-on" fluorescent probe based on carbon dots (CDs) and silver nanoparticles (AgNPs) mixture for sensitive and selective detection of cysteamine. By mixing AgNPs with CDs solution, the fluorescence of CDs was significantly decreased due to the inner filter effect (IFE). Upon addition of cysteamine to the mixed aqueous of CDs and AgNPs, the silver-sulfur bond between cysteamine and AgNPs caused AgNPs to aggregate, and the quenched fluorescence of CDs could in turn be recovered. The probe was employed to quantitatively detect cysteamine, and the results showed that it could detect cysteamine in a concentration range of 2-16 μM with the detection limit of 0.35 μM (signal-to-noise ratio of 3). The detection of cysteamine spiked into bovine serum samples showed high recovery rates ranging from 95.5 to 111.7%. More importantly, the developed probe had low cytotoxicity and was successfully used for in vivo imaging of HepG2 cells.

Recent Research in Ocular Cystinosis: Drug Delivery Systems, Cysteamine Detection Methods and Future Perspectives

Cystinosis is a rare genetic disorder characterized by the accumulation of cystine crystals in different tissues and organs. Although renal damage prevails during initial stages, the deposition of cystine crystals in the cornea causes severe ocular manifestations. At present, cysteamine is the only topical effective treatment for ocular cystinosis. The lack of investment by the pharmaceutical industry, together with the limited stability of cysteamine, make it available only as two marketed presentations (Cystaran® and Cystadrops®) and as compounding formulations prepared in pharmacy departments. Even so, new drug delivery systems (DDSs) need to be developed, allowing more comfortable dosage schedules that favor patient adherence. In the last decades, different research groups have focused on the development of hydrogels, nanowafers and contact lenses, allowing a sustained cysteamine release. In parallel, different determination methods and strategies to increase the stability of the formulations have also been developed. This comprehensive review aims to compile all the challenges and advances related to new cysteamine DDSs, analytical determination methods, and possible future therapeutic alternatives for treating cystinosis.

Challenges for cysteamine stabilization, quantification, and biological effects improvement

The aminothiol cysteamine, derived from coenzyme A degradation in mammalian cells, presents several biological applications. However, the bitter taste and sickening odor, chemical instability, hygroscopicity, and poor pharmacokinetic profile of cysteamine limit its efficacy. The use of encapsulation systems is a good methodology to overcome these undesirable properties and improve the pharmacokinetic behavior of cysteamine. Besides, the conjugation of cysteamine to the surface of nanoparticles is generally proposed to improve the intra-oral delivery of cyclodextrin-drug inclusion complexes, as well as to enhance the colorimetric detection of compounds by a gold nanoparticle aggregation method. On the other hand, the detection and quantification of cysteamine is a challenging mission due to the lack of a chromophore in its structure and its susceptibility to oxidation before or during the analysis. Derivatization agents are therefore applied for the quantification of this molecule. To our knowledge, the derivatization techniques and the encapsulation systems used for cysteamine delivery were not reviewed previously. Thus, this review aims to compile all the data on these methods as well as to provide an overview of the various biological applications of cysteamine focusing on its skin application.

A new nickel-based co-crystal complex electrocatalyst amplified by NiO dope Pt nanostructure hybrid; a highly sensitive approach for determination of cysteamine in the presence of serotonin

A highly sensitive electrocatalytic sensor was designed and fabricated by the incorporation of NiO dope Pt nanostructure hybrid (NiO–Pt–H) as conductive mediator, bis (1,10 phenanthroline) (1,10-phenanthroline-5,6-dione) nickel(II) hexafluorophosphate (B,1,10,P,1,10, PDNiPF6), and electrocatalyst into carbon paste electrode (CPE) matrix for the determination of cysteamine. The NiO–Pt–H was synthesized by one-pot synthesis strategy and characterized by XRD, elemental mapping analysis (MAP), and FESEM methods. The characterization data, which confirmed good purity and spherical shape with a diameter of ⁓ 30.64 nm for the synthesized NiO–Pt–H. NiO–Pt–H/B,1,10, P,1,10, PDNiPF6/CPE, showed an excellent catalytic activity and was used as a powerful tool for the determination of cysteamine in the presence of serotonin. The NiO–Pt–H/B,1,10, P,1,10, PDNiPF6/CPE was able to solve the overlap problem of the two drug signals and was used for the determination of cysteamine and serotonin in concentration ranges of 0.003–200 µM and 0.5–260 µM with detection limits of 0.5 nM and 0.1 µM, using square wave voltammetric method, respectively. The NiO–Pt–H/B,1,10,P,1,10,PDNiPF6/CPE showed a high-performance ability for the determination of cysteamine and serotonin in the drug and pharmaceutical serum samples with the recovery data of 98.1–103.06%.

Electrochemical Behavior and Detection of Diclofenac at a Microporous Si3N4 Membrane Modified Water–1,6-dichlorohexane Interface System

The electrochemical behavior when the liquid–liquid interface was modified by commercially available, microporous silicon nitride membrane, was achieved using cyclic voltammetry with tetramethyl ammonium. The transfer characteristics of the ionizable drug diclofenac ( DCF − ), as an anti-inflammatory, anti-rheumatic, antipyretic, and analgesic treatment in common use in biomedical applications, were also investigated across microporous silicon nitride-modified liquid interface. Thus, some thermodynamic variables for DCF − , such as the standard Gibbs energy of transfer, the standard transfer potential and lipophilicity were estimated. Furthermore, the influence of possible interfering substances (ascorbic acid, sugar, amino acid, urea, and metal ions) on the detection of DCF − was investigated. An electrochemical DCF sensor is investigated using differential pulse voltammetry (DPV) as the quantification technique, a linear range of 8–56 µM and a limit of detection of 1.5 µM was possible due to the miniaturized interfaces formed within silicon nitride.

Hydrogel Matrix-Grafted Impedimetric Aptasensors for the Detection of Diclofenac

Driven by the growing concern about the release of untreated emerging pollutants and the need for determining small amounts of these pollutants present in the environment, novel biosensors dedicated to molecular recognition are developed. We have designed biosensors using a novel class of grafted polymers, surface-attached hydrogel thin films, on conductive transducers as a biocompatible matrix for biomolecule immobilization. We showed that they can be dedicated to the molecular recognition of diclofenac (DCL). The immobilization of the aptamer onto surface-attached hydrogel thin films by covalent attachment provides a biodegradable shelter, providing the aptamer with excellent environments to preserve its active and functional structure while allowing the detection of DCL. The grafting of the aptamer is obtained using the formation of amide bonds via the activation of carboxylic acid groups of the poly(acrylic acid) hydrogel thin film. For improved sensitivity and higher stability of the sensor, a high density of the immobilized aptamer is enabled. The aptamer-modified electrode was then incubated with DCL solutions at different concentrations. The performances of the aptasensor were investigated by electrochemical impedance spectroscopy. The change in charge-transfer resistance was found to be linear with DCL concentration in the 30 pM to 1 μM range. The detection limit was calculated to be 0.02 nM. The improvement of the limit of detection can be mainly attributed to the three-dimensional environment of the hydrogel matrix which improves the grafting density of the aptamer and the affinity of the aptamer to DCL.

Fabrication of magnetic iron oxide-supported copper oxide nanoparticles (Fe3O4/CuO): modified screen-printed electrode for electrochemical studies and detection of desipramine

The present investigation examines a sensitive electrochemical technique to detect desipramine through Fe₃O₄/CuO nanoparticles (NPs). Fe₃O₄/CuO NPs were synthesized via a coprecipitation procedure, and the products were characterized via energy disperse spectroscopy, X-ray diffraction, transmission electron microscopy, scanning electron microscopy, and vibrating sample magnetometer. The voltage–current curve and differential pulse voltammetry examinations of Fe₃O₄/CuO-modified screen-printed electrode (Fe₃O₄/CuO/SPE) were followed by the determination of electro-catalytic activities toward desipramine oxidation in a phosphate buffer solution (pH = 7.0). In addition, the value of diffusion coefficient (D = 3.0 × 10⁻⁶ cm² s⁻¹) for desipramine was calculated. Then, based on the optimum conditions, it was observed that the currents of the oxidation peak were linearly proportionate to the concentration of desipramine in the broad range between 0.08 and 400.0 μM and LOD of 0.03 μM (S/N = 3). Finally, our new sensor was successfully utilized to detect desipramine in the real samples, with reasonable recovery in the range of 97.2% to 102.7%.

The present investigation examines a sensitive electrochemical technique to detect desipramine through Fe₃O₄/CuO nanoparticles.

Electrochemical Sensors, a Bright Future in the Fabrication of Portable Kits in Analytical Systems

Analysis of food, pharmaceutical, and environmental compounds is an inevitable issue to evaluate quality of the compounds used in human life. Quality of drinking water, food products, and pharmaceutical compounds is directly associated with human health. Presence of forbidden additives in food products, toxic compounds in water samples and drugs with low quality lead to important problems for human health. Therefore, attention to analytical strategy for investigation of quality of food, pharmaceutical, and environmental compounds and monitoring presence of forbidden compounds in materials used by humans has increased in recent years. Analytical methods help to identify and quantify both permissible and unauthorized compounds present in the materials used in human daily life. Among analytical methods, electrochemical methods have been shown to have more advantages compared to other analytical methods due to their portability and low cost. Most of big companies have applied this type of analytical methods because of their fast and selective analysis. Due to simple operation and high diversity of electroanalytical sensors, these types of sensors are expected to be the future generation of analytical systems. Therefore, many scientists and researchers have focused on designing and fabrication of electroanalytical sensors with good selectivity and high sensitivity for different types of compounds such as drugs, food, and environmental pollutants. In this paper, we described the mechanism and different examples of DNA, enzymatic and electro-catalytic methods for electroanalytical determination of drug, food and environmental compounds.

A new insight of structures, bonding and electronic properties for 6-mercaptopurine and Ag8 clusters configurations: a theoretical perspective

Background

Many reports have also shown that the silver nanoparticles can effectively increase the anticancer drug activity and intensely enhance the drug curative effect. The adsorption of 6MP on nanomaterials has received a lot of attentions because of the drug coordination to its chemotherapeutic activity. The geometrical structures, chemical bonds, molecular orbital properties as well as density of states for the configurations were analyzed to deeply understand the interactions between the 6MP and Ag₈ clusters for high effect anticancer drug production.

Results

In this work, the density functional theory B3LYP has been used to investigate the structures and properties of the configurations between 6-mercaptopurine (6MP) and Ag₈ clusters using 6-311++G** level as well as an effective pseudo potential LANL2DZ. The geometries of ten configurations were optimized with full freedom. The geometrical structures, chemical bonds, molecular orbital properties as well as density of states for partial configurations were analyzed based on the density functional calculations. Polarizable continuum solvent model (PCM) in self-consistent reaction field (SCRF) were used for the aqueous calculations. The influences of temperature and pressure on the stability of the predominant configurations in the gas phase were further considered using standard statistical thermodynamic methods from 50 to 500 K and at 1 bar or 100 bar.

Conclusion

The result shows that there are ten stable configurations in the gas phase and there is a strong chemical bond between a Ag and S atom in the most stable configuration. The analysis of density of states also shows that the Ag–S chemical bond in the most stable configuration has been formed. Moreover, the results show that the temperature and the pressure will significantly influence the stability of the configurations in the gas phase. Additionally, when the solvent effect was considered, we found that there are only seven stable configurations and the solvent have different effect on various configurations.

Electronic supplementary material

The online version of this article (10.1186/s13065-019-0573-z) contains supplementary material, which is available to authorized users.

Electroanalysis of Catecholamine Drugs using Graphene Modified Electrodes

Background:

Catecholamine drugs are a family of electroactive pharmaceutics, which are widely analyzed through electrochemical methods. However, for low level online determination and monitoring of these compounds, which is very important for clinical and biological studies, modified electrodes having high signal to noise ratios are needed. Numerous materials including nanomaterials have been widely used as electrode modifies for these families during the years. Among them, graphene and its family, due to their remarkable properties in electrochemistry, were extensively used in modification of electrochemical sensors.

Objective:

In this review, working electrodes which have been modified with graphene and its derivatives and applied for electroanalyses of some important catecholamine drugs are considered.

Ultrasonic energy-assisted preparation of β-cyclodextrin-carbon nanofiber composite: Application for electrochemical sensing of nitrofurantoin

A simple ultrasonic energy assisted synthesis of β-cyclodextrin (β-CD) supported carbon nanofiber composite (CNF) and its potential application in electrochemical sensing of antibiotic nitrofurantoin (NFT) is reported. The elemental composition and surface morphology of the β-CD/CNF composite was validated through Field emission scanning electron microscopy, energy dispersive X-ray microscopy, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, and thermogravimetric analysis. The uniform enfolding of hydrophilic β-CD over CNF enhance the aqueous dispersion and offer abundant active surface to the β-CD/CNF composite. Further, the electrocatalytic efficacy of the β-CD/CNF composite is utilized to fabricate an electrochemical sensor for the high sensitive quantitative detection of NFT. Under optimized analytical conditions, the sensor displays a broad working range of 0.004-308 µM and calculated detection limit of 1.8 nM, respectively. In addition, the sensor showcased a good selectivity, storage, and working stability, with amiable reproducibility. The point-of-care applicability of the sensor was demonstrated with NFT spiked human blood serum and urine sample with reliable analytical performance. The simple, cost-effective NFT sensor based on β-CD/CNF offered outstanding analytical performance in real-world samples with higher reliability.

Development of Novel Nanocomposites Based on Graphene/Graphene Oxide and Electrochemical Sensor Applications

Background:

Until now, several methods such as spectroscopic methods and chromatographic techniques have been developed for the determination of biomolecules, drug or heavy metals. Nevertheless, the crucial interference problems are present in these methods. Due to these reasons, more sensitive, favorable portability, low-cost, simple and selective sensors based on nanocomposites are needed in terms of health safety. In the development of electrochemical nanosensor, the nanomaterials such as graphene/graphene oxide, carbon and carbon nitride nanotubes are utilized to improve the sensitivity.

Objective:

The nanomaterials such as graphene/graphene oxide, carbon and carbon nitride nanotubes have important advantages such as high surface area, electrical conductivity, thermal and mechanical stability. Hence, we presented the highly selective methods for sensitive sensor applications by molecular imprinting technology in literature. This technology is a polymerization method around target molecule. This method provides the specific cavities to analyte molecule on the polymer surface. Hence, the selective sensor is easily created for biomedical and other applications. Novel electrochemical sensors based on nanocomposite whose surface is coated with Molecular Imprinting Polymer (MIP) are developed and then applied to the selective and sensitive detection in this study. Until now, we have presented several reports about nanocomposite based sensor with MIP.

Simultaneous Determination of Epinephrine and Tyrosine Using a Glassy Carbon Electrode Amplified with ZnO-Pt/CNTs Nanocomposite

Background:

Simultaneous analysis of epinephrine and tyrosine as two effective and important biological compounds in human blood and urine samples are very important for the investigation of human health.

Objective:

In this research, a highly effective voltammetric sensor fabricated for simultaneous analysis of epinephrine and tyrosine. The sensor was fabricated by the modification of glassy carbon electrode with ZnO-Pt/CNTs nanocomposite (ZnO-Pt/CNTs/GCE). The synthesized nanocomposite was characterized by SEM method. The ZnO-Pt/CNTs/GCE showed two separated oxidation signals at potential ~220 mV and 700 mV for epinephrine and tyrosine, respectively. Also, we detected linear dynamic ranges 0.5-250.0 µM and 1.0-220 µM with a limit of detections 0.1 µM and 0.5 µM for the determination of epinephrine and tyrosine, respectively. The ZnO-Pt/CNTs/GCE was used for the determination of epinephrine and tyrosine in blood serum and human urine samples.

Graphene Quantum Dots in Electrochemical Sensors/Biosensors

Background:

Graphene and its derivatives, as most promising carbonic nanomaterials have been widely used in design and making electrochemical sensors and biosensors. Graphene quantum dots are one of the members of this family which have been mostly known as fluorescent nanomaterials and found extensive applications due to their remarkable optical properties. Quantum confinement and edge effects in their structures also cause extraordinary electrochemical properties.

Objective:

Recently, graphene quantum dots besides graphene oxides and reduced graphene oxides have been applied for modification of the electrodes too and exposed notable effects in electrochemical responses. Here, we are going to consider these significant effects through reviewing some of the recent published works.

Voltammetric Sensors Based on Various Nanomaterials for the Determination of Sulfonamides

Background:

The widespread applications of sulphonamides, as antibacterial or antimicrobial agents, and their mechanism of actions in the body, have changed their determination to an important issue in the area of human health.

Objective:

Here, history of developing voltammetric sensors based on nanomaterials for the detection of sulfonamides including sulfadiazine, sulfamethoxazole, sulfacetamide, sulfadimethoxine, sulfathiazole, sulfamethiazole and sulfamerazine is reviewed. Modified electrodes based on various nanomaterials (carbonaceous nanomaterials, Metallic Nanoparticles (MNPs), conducting nanopolymers) have been reported, and studies showed that nanomaterials have been mostly used to overcome problems like the poor sensitivity and selectivity of bare electrodes. The study covers the properties of each sensor in detail, and reports and compares the linear ranges, Limits of Detection (LODs), reproducibility, and reusability of the electrodes reported so far.

Application of Advanced Electrochemical Methods with Nanomaterial-based Electrodes as Powerful Tools for Trace Analysis of Drugs and Toxic Compounds

Background:

The new progress in electronic devices has provided a great opportunity for advancing electrochemical instruments by which we can more easily solve many problems of interest for trace analysis of compounds, with a high degree of accuracy, precision, sensitivity, and selectivity. On the other hand, in recent years, there is a significant growth in the application of nanomaterials for the construction of nanosensors due to enhanced chemical and physical properties arising from discrete modified nanomaterial-based electrodes or microelectrodes.

Objective:

Combination of the advanced electrochemical system and nanosensors make these devices very suitable for the high-speed analysis, as motioning and portable devices. This review will discuss the recent developments and achievements that have been reported for trace measurement of drugs and toxic compounds for environment, food and health application.

Electrochemical Determination of Mycophenolate Mofetil in Drug Samples Using Carbon Paste Electrode Modified with 1-methyl-3-butylimidazolium Bromide and NiO/SWCNTs Nanocomposite

Background:

The mycophenolate mofetil is an immunosuppressant drug with wide application in the treatment of cancer and prevent rejection in organ transplantation. This drug showed many sides effects for pregnant women and determination of this drug is very important in the human body.

Objective:

A new electrochemical strategy was described for analysis of Mycophenolate Mofetil (MMF) using novel voltammetric sensor. The sensor was fabricated using NiO/SWCNTs and 1-methyl- 3-butylimidazolium bromide as two conductive mediators for modification of carbon paste electrode (NiO/SWCNTs/MBBr/CPE). The NiO/SWCNTs/MBBr/CPE can be used for analysis of MMF in aqueous buffer solution in the concentration range of 0.08-900 µM. In addition, the NiO/SWCNTs/ MBBr/CPE reduced oxidation over-potential of MMF ~ 80 mV and increased the oxidation current of MMF ~ 2.85 times. In the final step, NiO/SWCNTs/MBBr/CPE was used for determination of MMF in pharmaceutical serum and tablet samples.

A New Nanostructure Square Wave Voltammetric Platform for Determination of Tert-butylhydroxyanisole in Food Samples

Background:

Antioxidants are one of the important additives in food samples due to their role in protecting human cells against the effects of free radicals. The analysis of antioxidants is essential due to the role of antioxidants in improving body health.

Objective:

A square wave voltammetric sensor was fabricated for the determination of tert-butylhydroxyanisole (TBHA) based on the application of CdO/SWCNTs and 1-methyl-3-butylimidazolium chloride as mediators for the modification of carbon paste electrode (MBCl/CdO/SWCNTs/CPE). The MBCl/CdO/SWCNTs/CPE improved the sensitivity of TBHA ~ 6.7 times and showed a linear dynamic range 0.07-600 µM with detection limit 0.02 µA for the analysis of TBHA. The pH investigation confirmed that electro-oxidation of TBHA occurred by exchanging two electrons and two protons. In addition, the MBCl/CdO/SWCNTs/CPE was used for determination of TBHA in food samples.

A novel electrochemical epinine sensor using amplified CuO nanoparticles and an-hexyl-3-methylimidazolium hexafluorophosphate electrode

This study suggests a carbon paste electrode modified with CuO nanoparticles andn-hexyl-3-methylimidazolium hexafluorophosphate (CPE/CuO-NPs/HMIPF₆) as a powerful tool for the analysis of epinine for the first time.