Multi-walled Carbon Nanotube Ionic Liquid Research Articles

A computer-generated plan to develop an intelligent biosensor for investigation of the inhibition of renin by aliskiren: A journey from inhibition to biosensing

For the first time, a novel electrochemical biosensor was fabricated based on modification of a rotating glassy carbon electrode with multi-walled carbon nanotubes-ionic liquid, and molecularly imprinted polymers (MIPs) in which renin (Rn), and aliskiren (AK) were used as templates. By immersion the biosensor in Rn, AK, and their binary system (AK-Rn) solutions, the species (Rn, AK, and AK-Rn) were entrapped within the pathways of the MIPs. These processes and investigation of the inhibition of the Rn by AK helped us to obtain higher electrochemical signals for a good monitorization of the system. The effects of experimental parameters on response of the biosensor to AK were optimized by a small central composite design to obtain the highest response. Hydrodynamic cyclic voltametric (HCV), hydrodynamic differential pulse voltammetric (HDPV), and hydrodynamic linear sweep voltammetric (HLSV) data obtained and recorded in order to be analyzed by classical methods and multivariate curve resolution-alternating least squares (MCR-ALS) as an advanced chemometric method. The results of molecular dockings, classical and chemometric analyses confirmed that the Rn was strongly inhibited by the AK which was good evidence to develop a novel biosensing system for determination of Rn. A novel biosensor was developed for determination of the Rn which had an acceptable performance in determination of Rn in the range of 0–9 fM. This approach opened a new way for investigation of enzymes' inhibition, and developing a new generation of electrochemical biosensors for medical and biomedical applications.

A novel and intelligent chemometric-electrochemical-enzymatic biosensing procedure and mimicking a clinical condition environment to trick the red blood cells for counting them under physiological conditions: A new connection among chemometry, electrochemistry and hematology

Here, a novel electrochemical biosensing procedure has been developed for determination of the number of red blood cells (RBCs) under physiochemical conditions based on chemometric modeling of hydrodynamic differential pulse voltammetric (HDPV), and amperometric data as responses of a modified edge plane pyrolytic graphite electrode (EPPGE). In order to obtain a good sensitivity from the EPPGE, its surface was modified with a thin layer of multiwalled carbon nanotubes-ionic liquid (MWCNTs-IL). Catalase (CAT) was immobilized onto the surface of MWCNTs-IL/EPPGE with help of nafion. The response of the biosensor was based on electrochemical reduction of oxygen of the blood samples which was enhanced by a trick based on addition of hydrogen peroxide (H2O2) to blood samples which can be reduced by the CAT to produce extra oxygen. Prior to experiments, the solution in electrochemical cell was bubbled with pure N2 to purge the oxygen in the solution, but in order to increase the selectivity of the biosensor towards detection of the oxygen obtained from the red blood cells, voltammetric responses of the biosensor were modeled by multivariate chemometric calibration methods with the help of radial basis function-partial least squares (RBF-PLS), least squares-support vector machines (LS-SVM), recursive weighted partial least squares (rPLS), ant colony optimization-mathematical pre-processing selection by genetic algorithm-sample selection through a distance-based procedure-partial least squares-1 (ACO-GA-SS-PLS1), and radial basis function-artificial neural networks (RBF-ANN) to select the best method for determination of the number of the RBCs. The results confirmed the amperometric methods modeled by RBF-ANN showed the best performance for supporting the biosensor in determination of the number of the RBCs with a performance which had an excellent compatibility with the results of a hemocytometer. The results of this study as the newest application of chemometric-electrochemical methods can make a strong connection among electrochemists, chemometricians and hematologists to expand their collaborations on determination of blood factors.

An intelligent and novel electrochemical biosensor for simultaneous enzymatic biosensing of cholesterol and glucose in the presence of uric acid based on first-and second-order calibration methods

In this work, for the first time, a novel electrochemical biosensor was fabricated based on modification of a glassy carbon electrode with multi-walled carbon nanotubes-ionic liquid (MWCNTs-IL) which was used as a platform to the synthesis of molecularly imprinted polymers having glucose (GL), glucose oxidase (GO), cholesterol (CL), cholesterol oxidase (CO), cholesterol esterase (CE), horse radish peroxidase (HRP), and uric acid (UA) as template molecules. For simultaneous biosensing of GL and CL, the biosensor (MIPs/MWCNTs-IL/GCE) was incubated with the enzymes and then, it was individually incubated with GL and CL. Response of the biosensor was based on the reduction of the hydrogen peroxide produced from enzymatic reactions. Individual incubation of the biosensor with GL and CL generated two very similar peaks while its incubation with both GL and CL generated a single peak which needed to be assisted by first- and second-order calibration methods to choose the best method. Second-order hydrodynamic differential pulse voltammetric data were generated and modeled by MCR-ALS, PARASIAS, and PARAFAC2 to simultaneous determination of them in the presence of UA as uncalibrated interference based on exploiting second-order advantage. Amperometric responses of the biosensor to GL and CL were also calibrated and assisted by first-order calibration methods for simultaneous determination of GL and CL in the presence of UA based on exploiting first-order advantage. The result confirmed that the biosensor assisted by second-order data modeled by MCR-ALS showed the best performance for simultaneous determination of CL and GL in the presence of UA as uncalibrated interference in both synthetic samples and human serum samples which was comparable with HPLC-UV as the reference method. It should be noted the biosensor was able to simultaneous determination of CL and GL in the ranges of 0.5–15 pM and 1–18 pM with limits of detection of 0.81 pM and 0.23 pM, respectively, and response of the biosensor was stable, selective, ultrasensitive, repeatable, and reproducible. This work as the first report chemometric assisted enzymatic biosensing of GL and CL can be continued to develop more projects for biomedical purposes.

Chemometrics-assisted electrochemical biosensing of cholesterol as the sole precursor of steroids by a novel electrochemical biosensor

This project was performed with the aims of increasing the sensitivity of differential pulse voltammetry (DPV) which itself is a sensitive electroanalytical technique, and also to compare the area under peak (univariate calibration), height of peak (univariate calibration) and whole of vector (multivariate calibration) for calibration purposes. These topics were investigated by fabrication of a novel electrochemical biosensor for determination of cholesterol (CHO). The procedure used in this project was based on the synthesis of molecularly imprinted polymers (MIPs) to the preconcentration of CHO and its biosensing by a rotating glassy carbon electrode (GCE) modified by co-immobilization of cholesterol oxidase (CO), cholesterol esterase (CE) and horseradish peroxidase (HP) onto multiwalled carbon nanotubes-ionic liquid (COCEHP/MWCNTs-IL/GCE). The results showed that the hydrodynamic DPV (HYDPV) was much more sensitive than DPV and using the area under peak for univariate calibration purposes was more suitable than height of peak. Adsorption at the electrode surface is an important trouble which affects the height and position of voltammetric peaks, but the area under peak is not affected by adsorption therefore, it can be more suitable for univariate calibration purposes. The biosensor response was also calibrated by chronoamperometry and the results confirmed that the HYDPV was more sensitive than chronoamperometry. The next attempt was based on recording the biosensor responses based on second-order HYDPV data and modeling of them (whole of vectors) by three-way calibration methods which showed the best performance among the tested methods for determination of CHO. The biosensor response was long-term stable, repeatable and reproducible which was successfully applied to the analysis of serum sample towards determination of CHO whose results were comparable with a reference method.

A novel dual template molecularly imprinted modified pencil graphite electrode and assisting it by second-order calibration to construct a novel electronic device in advance for simultaneous determination of ferritin and transferrin

This work introduced a novel electronic device for simultaneous determination of ferritin and transferrin in real matrices. Here, a pencil graphite electrode was chosen as a platform and its surface was modified with multiwalled carbon nanotubes-ionic liquid and electrochemically reduced fullerene-C60. Finally, the surface of the biosensor was modified by dual template molecularly imprinted polymers which were produced by electropolymerization of 2-amino-5-mercapto-1, 3, 4-thiadiazole, and ferritin and transferrin as template molecules. To generate a square wave voltammetric signal from the biosensor to simultaneous determination of ferritin and transferrin, it was incubated into a solution having ferritin and transferrin and then, it was immersed into an electrochemical probe solution. By incubation of the biosensor with ferritin and transferrin, the pathways within its molecularly imprinted polymer layer were occupied by ferritin and transferrin therefore, it was reasonable to observe decreasing of the height of its square wave voltammetric response. Because of the nature of the square wave voltammetric data (potential shifts), incubation of the biosensor with ferritin and transferrin produced two severely overlapped peaks while incubation of the biosensor with both of them generated a single peak. Therefore, for simultaneous determination of ferritin and transferrin, the biosensor was assisted by three-way calibration with the help of second-order square wave voltammetric data which helped me to develop a very efficient electronic device for simultaneous determination of ferritin (sensitivity: 6.5 ​μA ​nM−1, limit of detection: 0.01 ​nM) and transferrin (sensitivity: 6.1 ​μA ​nM−1, limit of detection: 0.012 ​nM) in serum samples whose performance was comparable with a reference method.

Ionic Liquid-Multiwalled Carbon Nanotubes Nanocomposite Based All Solid State Ion-Selective Electrode for the Determination of Copper in Water Samples

A new copper sensitive all solid-state ion-selective electrode was prepared using multiwalled carbon nanotubes-ionic liquid (1-butyl-3-methylimidazolium hexafluorophosphate) nanocomposite as an additional membrane component. The effect of nanocomposite content in the membrane on the electrode parameters was investigated. The study compares, among others, detection limits, sensitivity, and the linearity ranges of calibration curves. Content 6 wt.% was considered optimal for obtaining an electrode with a Nernstian response of 29.8 mV/decade. An electrode with an optimal nanocomposite content in the membrane showed a lower limit of detection, a wider linear range and pH range, as well as better selectivity and potential stability compared to the unmodified electrode. It was successfully applied for copper determination in real water samples.

Comparative study of nitrate all solid state ion-selective electrode based on multiwalled carbon nanotubes-ionic liquid nanocomposite

Carbon nanotubes have enjoyed unflagging popularity in recent years. They are successfully used in many fields of science, including potentiometry for the construction of ion selective electrodes with solid contact. A new type of SC-ISEs sensitive to nitrate(V) ions using multiwalled carbon nanotubes-ionic liquid nanocomposite was prepared. The effect of the kind of carbon nanotubes on the parameters of SC-ISEs was investigated. The study compares, among others, detection limits, sensitivity and linearity ranges of characteristic curves, and stability of the potential measured for the tested electrodes. Electrochemical impedance spectroscopy and chronopotentiometric techniques were also used as research methods. It was found that the type of carbon nanotubes included in the nanocomposite influences both the metrological and electrical parameters of the obtained solid contact nitrate ion-selective electrode.

Fabrication of a novel amperometric sensing platform for determination of mangiferin

In this work, we have fabricated a novel amperometric platform for the sensing of mangiferin (MAG) based on application of an interesting modification strategy to a bare glassy carbon electrode (GCE). The first layer of the modification process consisted of loading of multiwalled carbon nanotubes-ionic liquid (MWCNTs-IL) onto the GCE surface which was then, modified with reduced fullerene C60 (C60). The C60/MWCNTs-IL/GCE was further modified with chitosan-IL (CS-IL) which was an excellent platform for electrodeposition of the Au and Pt nanoparticles (AuPt NPs). Our modification procedure allowed us to obtain AuPt NPs/CS-IL/C60/MWCNTs-IL/GCE as the sensing platform for determination of MAG in real samples. After characterization and confirmation of the modification process, the sensor response to MAG was calibrated by standard solutions which showed us that the sensor response was linear in the concentration range of 2–40 nM with a detection limit of 0.61 nM. After that, the sensor was applied to the determination of MAG in spiked human plasma samples which confirmed the capability of the sensor for determination of MAG in real samples. Our results confirmed that the sensor response was repeatable, reproducible, selective, sensitive and stable towards determination of MAG.

Chemometrical-electrochemical investigation for comparing inhibitory effects of quercetin and its sulfonamide derivative on human carbonic anhydrase II: Theoretical and experimental evidence

This paper reports results of a valuable study on investigation of inhibitory effects of the sulfonamide derivative of quercetin (QD) on human carbonic anhydrase II (CA-II) by electrochemical and chemometrical approaches. To achieve this goal, a glassy carbon electrode (GCE) was chosen as the sensing platform and different electrochemical techniques such as cyclic voltammetry (CV), differential pulse voltammetry (DPV), linear sweep voltammetry (LSV) and electrochemical impedance spectroscopy (EIS) were used to investigate and comparing inhibitory effects of quercetin (Q) and QD on CA-II. By the use of EQUISPEC, SPECFIT, SQUAD and REACTLAB as efficient hard-modeling algorithms, bindings of Q and QD with CA-II were investigated and the results confirmed that the QD inhibited the CA-II stronger than Q suggesting a highly relevant role of QD's-SO2NH2 group in inhibiting activity and also was confirmed by docking studies. Finally, a novel EIS technique based on interaction of Q and CA-II was developed for sensitive electroanalytical determination of CA-II and in this section of our study, the sensitivity of the developed electroanalytical methodology was improved by the modification of the GCE was with multi-walled carbon nanotubes-ionic liquid.

Highly Conductive Crown Ether/Ionic Liquid Crystal-Carbon Nanotubes Composite Based Electrochemical Sensor for Chiral Recognition of Tyrosine Enantiomers

A new insight is presented in the fabrication of a simple chiral electrochemical sensor for tyrosine enantiomers which are the biomarkers of depression. The conductive sensor is based on modifying the glassy carbon electrode with two consecutive layers namely multi-walled carbon nanotubes-ionic liquid crystal (CNT+ILC) and 18-crown-6 (CW); GC/(CNT+ILC)/CW. CW is introduced for the first time as an excellent receptor for the chiral recognition of Ty enantiomers due to its perfect host-guest size matching principle. On the other hand, β-cyclodextrin (β-CD) does not recognize Ty enantiomers as its cavity size was larger, and needs extra modifications. Moreover, it was observed due to the opposite steric configurations of the Ty enantiomers, CW preferably forms strong complexes with L-Ty compared to D-Ty enantiomers, resulting in significantly noticeable electrochemical differences in their peak current responses with ratio of (L-Ty to D-Ty) about 3.09. The GC/(CNT+ILC)/CW showed excellent current responses for the electrochemical analysis of L-Ty and D-Ty enantiomers in the concentration ranges of 0.01–60 μmol L−1 and 0.09–60 μmol L−1 with low detection limit values of 1.42 nmol L−1and 9.36 nmol L−1, respectively. The practical impact of the sensor was illustrated in accurate determination of the percentage of enantiomers in Ty racemic mixture. Moreover, the electro-oxidation of AA, UA, and L-Ty in their ternary mixture was successfully achieved to three well-separated peaks using the GC/(CNT+ILC)/CW sensor.

Determination of Tryptophan by Using of Activated Multi-Walled Carbon Nanotube Ionic Liquid Electrode

Determination of tryptophan was performed by using of an easy to prepared electrode. Basically, the electrode was prepared by using of ionic liquid and multi-walled carbon nanotube as main constituents. Then, the electrode surface was activated by cycling the potential. The activated multi-walled ionic liquid electrode shows facile electro-oxidation and good stability for determination of tryptophan. Linear range and limit of detection were obtained as 5 × 10–6 to 1 × 10–3 and 2.3 × 10–6 M, respectively. Finally, determination of tryptophan in real samples (commercial amino acid injection and blood serum) was performed successfully. The high activity of the proposed electrode is attributed to the simultaneous presence of ionic liquid and multi-walled carbon nanotube in the electrode content.

Electrochemical Method for the Determination of Three New Anti-Hepatitis C Drugs: Application in Human Blood Serum

Recently, there is a widespread usage of anti-hepatitis C drugs in the world where the disease is classified as epidemic and life threatening. Direct-acting antivirals drugs, (DAAs), are introduced as promising medication regimens to treat chronic HCV infection. From the clinical point of view, it is necessary to introduce reliable method for the determination of the three new drugs: Daclatasvir (DAC); Sofosbuvir (SOF); and Ledipasvir (LED). For the first time a simple, reliable, time efficient, direct and ultrasensitive sensor is designed for the determination of DAAs. The sensor is constructed by applying a thin layer from a mixture of multi-walled carbon nanotubes-ionic liquid crystal to glassy carbon electrode-surface followed by electrodeposition of cobalt nanoparticles (GC/(CNTs-ILC)/Co). The sensor exhibited excellent electro-catalytic activity toward LED, DAC and SOF determinations in human serum in wide linear dynamic ranges. The detection limits for LED, DAC and SOF were found as: 0.277 nmol L−1, 1.86 nmol L−1 and 7.29 nmol L−1 respectively. The GC/(CNTs-ILC)/Co sensor has been applied for the simultaneous determination of LED with SOF and in presence of interfering compounds. Furthermore, the application was extended to analysis of combination from LED and SOF in its pharmaceutical formulation.

Electrochemical determination of luteolin in Chrysanthemum using multi-walled carbon nanotubes–ionic liquid composite electrode

A multi-walled carbon nanotubes–ionic liquid composite electrode was constructed for the determination of trace-levels of luteolin in Chrysanthemum.

Highly sensitive determination of perphenazine on a carbon nanocomposite ionic liquid electrode

A multi-walled carbon nanotube–ionic liquid nanocomposite was fabricated for the electrochemical detection of perphenazine, suitable for the analysis of pharmaceuticals and blood serum samples.

A novel signal amplification strategy of an electrochemical immunosensor for human chorionic gonadotropin, based on nanocomposites of multi-walled carbon nanotubes–ionic liquid and nanoporous Pd

A novel electrochemical immunosensor using MWCNTs–BMIMPF6/NP-Pd as a sensor platform to sequentially immobilize antibodies was developed for hCG detection.

Electrochemical behavior of lansoprazole at a multiwalled carbon nanotubes-ionic liquid modified glassy carbon electrode and its electrochemical determination

The electrochemical behavior of lansoprazole (LNS) has been investigated at a glassy carbon electrode (GCE) and the electrode modified by a gel containing multiwalled carbon nanotubes (MWCNTs) and an room-temperature ionic liquid (RTIL) of 1-Butyl-3-methylimidazolium hexafluorophosphate (BMIMPF6) in 0.10 M phosphate buffer solution of pH 6.8. It was found that an irreversible anodic oxidation peak with Epa as 1.060 V appeared at MWCNTs-RTIL/GCE. Under the optimized experimental conditions a linear calibration curve were obtained over the concentration range from 5.0 ?M to 0.20 mM by differential pulse voltammetry with the limit of detection (LOD, S/N = 3) as 0.28 ?M. In addition, the novel MWCNTs-RTIL/GCE was also characterized by the electrochemical impedance spectroscopy and the proposed method has been successfully applied in the electrochemical quantitative determination of LNS content in commercial tablet samples and the determination results could meet the determination requirement.

Nitrite electrochemical sensor for food analysis based on direct immobilization of hemoglobin on multi-walled carbon nanotube ionic liquid electrode

A novel nitrite biosensor was constructed by simultaneous immobilization of hemoglobin (Hb) and a room temperature ionic liquid, octylpyridinium chloride ([OcPy][Cl]), on multi-walled carbon ionic liquid electrode (MWILE). The direct electron transfer of Hb showed a pair of redox peaks with a formal potential of −0.187 V vs. Ag/AgCl in pH 5.0 acetate buffer solution. Nitrite (NO2 −) catalysis on the modified electrode was investigated by cyclic voltammetry and amperometry. The biosensor exhibited a wide linear range for NO2 − detection from 0.01 to 15 mM, with a detection limit (3σ) of 1.46 μM. MWILE provided an excellent matrix for protein immobilization and biosensor fabrication which could be used for the determination of NO2 − with a low detection limit, fast response, long linearity, and excellent sensitivity.

Carbon Nanotube–Ionic Liquid (CNT–IL) Nanocamposite Modified Sol-Gel Derived Carbon-Ceramic Electrode for Simultaneous Determination of Sunset Yellow and Tartrazine in Food Samples

Carbon-ceramic electrode modified with multi-walled carbon nanotubes–ionic liquid (MWCNTs–IL) nanocomposite was constructed. This electrode was used for electrochemical determination of food dyes Sunset Yellow (SY) and tartrazine (Tz). The modified electrode based on high surface area and high ionic conductivity of nanocomposite exhibited electrocatalytic effect for oxidation of SY and Tz; also, oxidation peak potentials of SY and Tz effectively separated on modified electrode, and their simultaneous determination was possible. Operational parameters, such as the amount of MWCNTs in suspension, IL volume, solution pH, and scan rate, which affect the analytical performance of determination, were optimized. The present electrode behaved linearly to Sunset Yellow and tartrazine in the concentration range of 4 × 10−7 to 1.1 × 10−4 M and 3 × 10−6 to 0.7 × 10−4 M with a detection limit of 10−7 M (0.045 mg L−1) and 1.1 × 10−6 M (0.59 mg L−1), respectively. The proposed method was successfully utilized for simultaneous determination of SY and Tz in different food samples, and the obtained results were in good agreement to those obtained by HPLC method.

Direct electrochemistry of adenine on multiwalled carbon nanotube–ionic liquid composite film modified carbon paste electrode and its determination in DNA

A novel, simple and reliable sensor based on multiwalled carbon nanotube–ionic liquid (1-ethyl-3-methylimidazolium hexafluorophosphate, EMIMPF6) composite film modified carbon paste electrode (MWCNT–IL/CPE) was proposed for direct electrooxidation behavior and determination of adenine. Compared with unmodified electrode, the modified electrode not only significantly enhanced the oxidation peak current but also lowered its oxidation peak potential. The electrochemical behavior of adenine on the modified electrode was carefully studied by cyclic voltammetry and the electrochemical parameters such as the electron transfer coefficient (α), the electrode reaction standard rate constant (ks), the area of the electrode (A), the electron transfer number (n) and the concentration of the electroactive adenine (ГT) were calculated with the results of 0.36, 3.65×10−6s−1, 1.4×10−3cm2, 2.04 and 7.43×10−9molcm−2 respectively. By using differential pulse voltammetry (DPV) as the detection method, a linear relationship was obtained between the oxidation peak current and the adenine concentration in the range from 5.0×10−7 to 7.5×10−5molL−1 with the detection limit of 1.089×10−9molL−1 (3σ) and the relative standard deviation (RSD) 6.5% (n=7) of 5×10−5molL−1 for adenine. The common coexisting substances showed no interferences to the adenine detection and the modified electrode showed good ability to distinguish the electrochemical response of adenine.

Preparation and characterization of AuPt alloy nanoparticle–multi-walled carbon nanotube–ionic liquid composite film for electrocatalytic oxidation of cysteine

Gold–platinum (AuPt) alloy particles were fabricated directly on multi-walled carbon nanotubes (MWNT)–ionic liquid (i.e., trihexyltetradecylphosphonium bis(trifluoromethylsulfonyl)imide, [P6,6,6,14][NTf2]) composite coated glassy carbon electrode (GCE) by electrodeposition method. Scanning electron microscope image showed that they were well-dispersed nanocluster consisting of smaller nanoparticles, and their size was about 70 nm. X-ray diffraction experiment showed that they were single-phase alloy nanomaterial, and the calculated composition was consisting with that obtained by energy dispersive X-ray spectroscopy. The resulting modified electrode (i.e., AuPt–MWNT–[P6,6,6,14][NTf2]/GCE) presented high catalytic activity for the electrochemical oxidation of cysteine. The peak potential of cysteine shifted to 0.42 V (versus saturated calomel electrode) in 0.1 M H2SO4 and the peak current increased greatly in comparison with that on the corresponding Pt (or Au)–MWNT–[P6,6,6,14][NTf2]/GCE. Under the optimized conditions, the oxidation current of cysteine at 0.45 V was linear to its concentration in the range of 5.0 × 10−7 ∼ 4.0 × 10−5 M with a sensitivity of 43.8 mA M−1.