Intrinsic dual emissive insulin capped Au/Ag nanoclusters as single ratiometric nanoprobe for reversible detection of pH and temperature and cell imaging.

pH and temperature are two important characteristics in cells and the environment. These, not only in the well-done regulation of cell functions but also in diagnosis and treatment, have a key role. Protein-protected bimetallic nanoclusters are abundantly used in the building of biosensors. However, insulin-stabilized Au-Ag nanoclusters with dual intrinsic emission have not been investigated yet. In this work, Dual emissive insulin templated Au-Ag nanocluster (Ins(Au/Ag)NCs) were first synthesized in a simple and green one-put manner. The two emission wavelengths of, as-prepared NCs centered at 410 and 630 nm, excited in one excitation wavelength (330 nm). These two emission peaks were assigned to the di-Tyrosine cross-linked formation and bimetallic nanoclusters respectively. Further analysis displayed that each emission band of Ins(Au/Ag)NCs responded to one variable whilst another peak remained constant; For blue and red emission wavelengths, pH dependency and thermo-responsibility were observed respectively. As-prepared nanoprobe with the intrinsic dual emissive feature was used for ratiometric determination of these parameters, each with a discrete response from another. The linear range of 6.0-9.0 for pH and 1 to 71 °C for temperature was obtained, which comprises the physiological range of pH and temperature and afforded intracellular sensing and imaging capability. As-prepared NCs probe show excellent biocompatibility and cell membrane permeability, and so were successfully applied as direct ratiometric pH and temperature probes in HeLa and HFF cells. More interestingly, this dual emissive nanoprobe is capable of distinguishing cancer cells from normal ones.

Silanized fiberglass modified by carbon dots as novel and impressive adsorbent for aqueous heavy metal ion removal.

This work discusses the application of a silanized fiberglass (SFG) modified by carbon dots (CDs) as an effective adsorbent for up-taking some heavy metal ions including lead (Pb2+), chromium (Cr3+), cadmium (Cd2+), cobalt (Co2+), and nickel (Ni2+) as pollutant in the aqueous solution by batch method. Removal tests were carried out after optimization of pH, contact time, initial concentration of metal ions, and CDs amount. The SFG modified with CDs (CDs-SFG) was applied for the removal of 10 ppm of each metal ion solution after 100 min and the corresponding results showed the removal efficiencies of 100, 93.2, 91.8, 90, and 88.3% for Pb2+, Cd2+, Cr3+, Co2+, and Ni2+, respectively. The adsorption capacity of CDs-SFG in the metal ion mixed solution was also evaluated, and the results indicated the same trend in the adsorption capacity for metal ions in the mixed solution, though with lower absolute values compared to the single metal solutions. Moreover, the selectivity of this adsorbent for the adsorption of Pb2+ was almost twice of other tested metal ions. The regeneration of the CDs-SFG showed that its adsorption capacity after five cycles was reduced about 3.9, 6.0, 6.8, 6.7, and 8.0% for Pb2+, Cd2+, Cr3+, Co2+, and Ni2+, respectively. Finally, the applicability of the CDs-SFG adsorbent was examined with the analysis of the metal ions in water and wastewater samples.

High performance electrochemical method for simultaneous determination dopamine, serotonin, and tryptophan by ZrO2-CuO co-doped CeO2 modified carbon paste electrode.

In this research, a paste containing ZrO2-CuO-CeO2 ternary nanocomposite and graphene (Gr) was used in constructing a carbon paste sensor for monitoring biomolecules including dopamine (Dop), serotonin (Ser) and tryptophan (Trp). The scanning electron microscope (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffraction (XRD) were utilized for ZrO2-CuO-CeO2 ternary nanocomposite characterization. The obtained data show that, the ZrO2-CuO-CeO2/Gr and synergetic effect of using these three-metal oxide nanoparticles, could effectively improve the electron transfer kinetic and exhibit a high electrocatalytic activity, making it serve as a powerful tool for biomolecules analysis. The differential pulse (DP) and cycle voltammetry (CV) methods were applied for investigating electrochemical treatment of the analytes. In comparison to all of the previous voltammetric reports, this research has the lowest detection limit and widest linear range. The calibration curves in the optimum conditions were linear over the range of 0.008-7.2 and 7.2-185 µM for Dop, 0.008-7.9 and 7.9-205 µM for Ser and 0.009-8.6 and 8.6-194 µM for Trp. The calculated limit of detection (LOD) was 3.09, 3.49 and 5.32 nM for Dop, Ser and Trp, respectively. The applicability of this sensing device was tested by monitoring Dop, Ser and Trp in the human urine and plasma samples. The recovery percentage of the analysis in the real samples was between 95.6 and 104.74; also, the data of determination of Dop, Ser and Trp with ZrO2-CuO-CeO2/Gr/CPE was well close to HPLC data. The obtained result demonstrates that the ZrO2-CuO-CeO2/Gr/CPE has good selectivity, stability, reproducibility, and repeatability, and can be used for the routine analysis of Dop, Ser and Trp.

Introduction of a thrombin sensor based on its interaction with dabigatran as an oral direct thrombin inhibitor.

Dabigatran (DAB) is a direct thrombin inhibitor used for preventing blood clots and emboli after orthopedic surgery. The DAB - thrombin interaction was followed by fluorescence and UV-Vis spectroscopic methods. The binding of DAB to thrombin was also modeled by the molecular docking method. The obtained experimental results were consistent with theoretical results. The voltammetric method was also tested for DAB - thrombin interaction. Based on voltammetric findings, carbon paste electrode containing graphite powder, paraffin oil, MWCNTs, and DAB was constructed and used for thrombin monitoring after investigation of the DAB oxidation mechanism for the first time. The decrease in the linear sweep voltammetric (LSV) peak current of DAB in the presence of thrombin was utilized for the thrombin analysis. The calibration plot was linear in the concentration range of 1 to 70 nM (R2 = 0.9992) by LSV technique with a detection limit of 0.3 nM. The applicability of the proposed sensor was evaluated by the determination of thrombin in human serum as a real sample.

A highly selective green supported liquid membrane by using a hydrophobic deep eutectic solvent for carrier-less transport of silver ions.

A new supported liquid membrane (SLM) was designed by using a suitable deep eutectic solvent (DES) as the hydrophobic liquid membrane phase for the selective and facilitated carrier-less transport of Ag+ ions. The deep eutectic solvent was composed of a 4/1 molar ratio of l-menthol/salicylic acid and was impregnated into a microporous polypropylene membrane to prepare a novel carrier-less SLM system. The highly selective facilitated transport of silver ions was accomplished by using sodium thiosulfate as a highly selective stripping agent for Ag+ ions in the aqueous strip phase (SP). Some important factors, including the concentration of picric acid in the feed phase (FP), pH of the two aqueous phases, stirring rate, transport time, and nature and concentration of the stripping agent were also investigated and optimized. In the presence of 2.8 × 10-2 mol L-1 picrate ions as an appropriate ion pairing agent in the FP and 0.025 mol L-1 thiosulfate as a convenient metal ion acceptor in the SP, the amount of Ag+ ion transport found to occur almost quantitatively after 60 min is 90%. Compared with other SLM systems reported in the literature, the designed DES-SLM system exhibited suitable permeability and higher selectivity for Ag+ ion transport from aqueous solutions containing Fe2+, Mn2+, Cu2+, Ni2+, Pb2+, and Cd2+ as competing metal ions.

Enzyme-less amperometric sensor manufactured using a Nafion-LaNiO3 nanocomposite for hydrogen peroxide.

In the present study, an enzyme-less amperometric sensor based on Nafion (NF) and a LaNiO3 (LNO) nanocomposite was constructed for H2O2 detection. LNO from the perovskite group was mixed with NF as an effective solubilizing and stabilizing agent that was used as a novel modifier for modification of the glassy carbon electrode (GCE). The designed sensor showed a desirable electrocatalytic response toward H2O2 reduction. The calibration curve revealed two linear portions in the concentration ranges of 0.2-50 µM and 50-3240 µM, and the detection limit was 0.035 µM. The accuracy of the interference-free sensor was checked by recovery analysis in serum samples.

A sensitive electrochemical genosensor for highly specific detection of thalassemia gene.

Beta thalassemias (ßth) are the result of mutations in the ß-globin gene. In this report, an electrochemical genosensor was made to detect the sequences anent with the ß-globin gene. This biosensor is based on immobilizing 20-mer single stranded oligonucleotide (probe) on the Au nanoparticles- poly (4-aminothiophenol)/ reduced graphene oxide/glassy carbon electrode (AuNPs-PAT/rGO/ GCE) and hybridizing this oligonucleotide along with its complementary sequence (target). The vastness of the probe and target sequences hybridization was studied through differential pulse voltammetry (DPV) along with electrochemical impedance spectroscopy (EIS) using the [Fe(CN)6]3-/4- (1:1) as a hybridization index. The biosensor indicated great efficiency with significant sensitivity along with favorable selectivity. The DPV and EIS responses with the intended concentrations of the sequence were linear varying from 1.0 pM to 400.0 pM (Ip ν log C) and 0.5-400.0 pM (∆Rct ν log C) with a limit of detection of 0.06 pM and 0.035 pM, at the signal to noise ratio of 3σ. The biosensor of the DNA indicated proper discrimination capability to mismatched two-base, three-base, and non-complementary sequences.

Determination of Hg2+ and Cu2+ ions by dual-emissive Ag/Au nanocluster/carbon dots nanohybrids: Switching the selectivity by pH adjustment.

An innovative dual-emissive ratiometric nanohybrid probe comprised of red-emitting a (Ag/Au)@insulin nanoclusters (NCs) and blue-emitting carbon dots (CDs) was designed for sensitive and selective ratiometric determination of Hg2+ and Cu2+ ions.The fluorescence intensity of CDs (λex = 340 nm; λem = 420 nm) was unaffected in the presence of the metal ions tested, whereas the red emitting NCs (λex = 340 nm; λem = 640 nm) was strongly quenched by both Cu2+ and Hg2+ ions. Interestingly, the selectivity of the probe toward these two ions was simply switched by controlling the pH of probe solution without using any chelating agent. The probe selectively responded to Hg2+ ions at acidic condition (pH = 4.0), Cu2+ ions at basic condition (pH = 10.0), and Hg2+-Cu2+ mixtures at pHs within this range. The respective detection limitsfor determination of Cu2+ and Hg2+ ions at their specific pH conditions were estimated as 5 nM and 7 nM, over linear ranges of 20-600 nM and 20-2000 nM, respectively. The fabricated ratiometric probe also showed distinguished fluorescence color changes to visual detection of these ions. Finally, the probe was successfully applied to determination of Hg2+ and Cu2+ ions in tap and mineral water samples.

Fabrication of a glycation induced amyloid nanofibril and polyalizarin yellow R nanobiocomposite: Application for electrocatalytic determination of hydrogen peroxide.

Amyloid fibrils were produced in a solution of bovine serum albumin (BSA) in buffer solution in the presence of fructose. The solution was incubated for 20 weeks in the dark. We used glycation induced bovine serum albumin in which fibrilogenesis (nano fibrils) followed by using fluorescence (Thioflavin T), Dynamic Light Scattering (DLS) and Transmission Electron Microscopy (TEM) to achieve the size and morphology of fibrils. A novel electrochemical biosensor for the detection of hydrogen peroxide was developed based on immobilizing poly (alizarin yellow R) and amyloid nano-fibrils on glassy carbon electrode (PAYR/AMLNFibs/GCE). The electrocatalytic response of the biosensor was proportional to the hydrogen peroxide concentration in the range of 1 µM to 2.2 mM with a limit of detection and sensitivity of 290 nM and 0.024 µA/µM, respectively. The modified electrode demonstrated many advantages such as high sensitivity, low detection of limit and excellent catalytic activity.

Simultaneous electrochemical sensing of warfarin and maycophenolic acid in biological samples.

In this study, for the first time a rapid, selective and highly sensitive method was developed for simultaneous determination of warfarin and mycophenolic acid using carbon paste electrode modified by ß-cyclodextrin/multi-walled carbon nanotubes/cobalt oxide nanoparticles (ß-CD/MWCNTs/Co3O4NPs/CPE). The oxidation peaks of desired drugs was separated enough using the constructed electrode. Cyclic voltammetry (CV) and differential pulse voltammetry (DPV) were utilized for study the electrochemical response of the fabricated electrode and its surface modification was investigated by electrochemical impedance spectroscopy (EIS). Under optimal conditions, the adsorptive stripping voltammetric responses were linear in the concentration ranges 0.05-150 µM and 0.5-200 µM for WAR and MPA, respectively. The correlation coefficients were greater than 0.99. The limits of detection for WAR and MPA were 0.02 and 0.03 µM. The fabricated electrode was applied for the simultaneous determination of WAR and MPA in urine and human serum samples with satisfactory results.

Mycophenolate mofetil sensor based on molecularly imprinted polymer/multi-walled carbon nanotubes modified carbon paste electrode.

Using square wave voltammetry, a carbon paste electrode modified by molecularly imprinted polymer (MIP) as a recognition element of mycophenolate mofetil (MMF) and multi-walled carbon nanotubes was used for MMF monitoring To investigate the electrode during modification, electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) were utilized. After optimization of the effective parameters, the anodic peak current of MMF was utilized for dynamic range study which was linear in 9.9 nM-87 µM range. The detection limit of the sensor was 7.0 nM. The capture ability of MIP to target was compared with that of non-imprinted polymer (NIP). The practical application of the sensor in biological fluid samples analysis demonstrates its selectivity, sensitivity, and stability.

Intellectual modifying a bare glassy carbon electrode to fabricate a novel and ultrasensitive electrochemical biosensor: Application to determination of acrylamide in food samples.

Acrylamide (AA) is a neurotoxin and carcinogen which is mainly formed in foods containing large quantities of starch processed at high temperatures and its determination is very important to control the quality of foods. In this work, a novel electrochemical biosensor based on hemoglobin-dimethyldioctadecylammonium bromide (HG-DDAB)/platinum-gold-palladium three metallic alloy nanoparticles (PtAuPd NPs)/chitosan-1-ethyl-3-methylimidazolium bis(trifluoromethylsulfonyl)imide (Ch-IL)/multiwalled carbon nanotubes-IL (MWCNTs-IL)/glassy carbon electrode (GCE) is proposed for ultrasensitive determination of AA in food samples. Development of the biosensor is based on forming an adduct by the reaction of AA with α-NH2 group of N-terminal valine of HG which decreases the peak current of HG-Fe+3 reduction. The modifications were characterized by electrochemical impedance spectroscopy (EIS), cyclic voltammetry (CV), energy dispersive X-ray spectroscopic (EDS) and scanning electron microscopy (SEM). Under optimized conditions, the biosensor detected AA by square wave voltammetry (SWV) in two linear concentration ranges of 0.03-39.0nM and 39.0-150.0nM with a limit of detection (LOD) of 0.01nM. The biosensor was able to selective detection of AA even in the presence of high concentrations of common interferents which confirmed that the biosensor is highly selective. Also, the results obtained from further studies confirmed that the proposed biosensor has a short response time (less than 8s), good sensitivity, long term stability, repeatability, and reproducibility. Finally, the proposed biosensor was successfully applied to determine AA in potato chips and its results were comparable to those obtained by gas chromatography-mass spectrometry (GC-MS) as reference method.

Experimental and Computational Evidence on the Interaction of Cycloalkyl α-Aminobisphosphonates with Calf Thymus DNA.

Fluorescence spectroscopy, ultraviolet-visible absorption spectroscopy, circular dichroism spectroscopy, viscometry, cyclic voltammetry, and differential pulse voltammetry were applied to investigate the competitive interaction of DNA with the three new cycloalkyl α-aminobisphosphonates (D1-D3) and spectroscopic probe, neutral red dye, and Hoechst (HO), in a Tris-hydrogen chloride buffer (pH 7.4). The spectroscopic and voltammetric studies showed that the groove binding mode of interaction is predominant in the solution containing DNA and α-aminobisphosphonates. Furthermore, the results indicated that α-aminobisphosphonate with the lengthy N alkyl chains and larger heterocyclic ring size had a stronger interaction. The principal component analysis and theoretical quantum mechanical and molecular mechanics (QM-DFT B3LYP/6-31+G* and MM-SYBYL) methods were also applied to determine the number of chemical components presented in complexation equilibrium and identify the structure complexes of DNA with the three new cycloalkyl α-aminobisphosphonates (D1-D3), respectively.

A novel voltammetric sensor for nevirapine, based on modified graphite electrode by MWCNs/poly(methylene blue)/gold nanoparticle.

In the present study, a graphite electrode (GE) modified by conductive film (containing functionalized multi-walled carbon nanotubes (f-MWCNTs), poly methylene blue p(MB) and gold nanoparticles (AuNPs)) was introduced for determination of nevirapine (NVP) as an anti-HIV drug by applying the differential pulse anodic stripping voltammetry (DPASV) technique. Modification of the electrode was investigated by scanning electron microscopy (SEM) and impedance electrochemical spectroscopy (EIS). All electrochemical effective parameters on detection of NVP were optimized and the oxidation peak current of drug was used for its monitoring. The obtained results confirmed that the oxidation peak currents increased linearly by increasing in NVP concentrations in the range of 0.1-50 µM and a detection limit of 53 nM was achieved. The proposed sensor (AuNPs/p(MB)/f-MWCNTs/GE) was successfully applied for the determination of NVP in blood serum and pharmaceutical samples. It revealed the excellent stability, repeatability and reproducibility as well.

Introduction of a carbon paste electrode based on nickel carbide for investigation of interaction between warfarin and vitamin K1.

In this paper a novel electrochemical sensor based on nickel carbide (Ni3C) nanoparticles as a new modifier was constructed. Ni3C nanoparticle was synthesized and characterized by scanning electron microscopy, X-ray diffraction and first-principles study. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) studies confirmed the electrode modification. Afterwards, the new electrode for the first time was used for interaction study between vitamin K1 and warfarin as an anticoagulant drug by differential pulse voltammetry. The adduct formation between the drug and vitamin K1 was improved by decreasing in anodic peak current of warfarin in the presence of different amounts of vitamin K1. The binding constant between warfarin and vitamin K1 was obtained by voltammetric and UV-vis and fluorescence spectroscopic methods. The molecular modeling method was also performed to explore the structural features and binding mechanism of warfarin to vitamin K1. The different aspects of modeling of vitamin K1 and warfarin and their adduct structures confirmed the adduct formation by hydrogen bonding.

Adsorptive anodic stripping differential pulse voltammetric determination of CellCept at Fe3O4 nanoparticles decorated multi-walled carbon nanotubes modified glassy carbon electrode.

A simple and sensitive method based on adsorptive anodic stripping differential pulse voltammetry (AASDPV) for the determination of cellcept, using a magnetic Fe3O4 nanoparticles and functionalized (carboxylated) multi-walled carbon nanotubes modified glassy carbon electrode (f-MWCNs/Fe3O4/GCE) was developed. In phosphate buffer solution (pH = 5), the voltammogram of cellcept exhibited tow anodic peaks and the well-defined peak at about 0.611 V vs SCE was used for its monitoring. The modified electrode was characterized by different methods such as electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM) and cyclic voltammetry (CV). The experimental parameters, such as pH, deposition potential and time, as well as scan rate were optimized. Under the optimized conditions, Ip (µA) was proportional to the cellcept concentration in the range of 0.05-200 µM (R2 = 0.9989) with a detection limit of 9.0 nM and limit of quantification of 30.2 nM. The recovery was >98%. The practical analytical utilities of the modified electrode were demonstrated by the determination of cellcept in human urine and blood serum samples. Modified electrode showed an adequate sensitivity and stability for evaluated samples.

A novel voltammetric sensor for citalopram based on multiwall carbon nanotube/(poly(p-aminobenzene sulfonic acid)/ß-cyclodextrin).

Multi-walled carbon nanotube (MWCNTS) coated with poly p-aminobenzene sulfonic acid/ß-cyclodextrin (p-ABSA/ß-CD) film was used as an effective strategy for modification of the surface of glassy carbon electrode (GCE). Electrochemical study and determination of citalopram (CT) were investigated at the p (p-ABSA)/ß-CD/MWCNT/GC using cyclic and differential pulse anodic stripping voltammetric techniques. The results indicate that the p (p-ABSA)/ß-CD/MWCNT/GC significantly enhanced the oxidation peak current of CT. The modified electrode was characterized by electrochemical impedance spectroscopy (EIS), scanning electron microscopy(SEM) and cyclic voltammetry (CV).The fabricated electrochemical sensor exhibits a fast and reversible linear response toward CT within the concentration ranges of 90 nM-1 µM, 1-11 µM and 11-100 µM with correlation coefficients greater than 0.99 and detection limit of 44 nM. The resulting functionalized polymer film features interesting electrochemical properties such good recovery, reproducibility and selectivity toward CT. The applicability of the proposed sensor was tested by determination of CT in pharmaceutical combinations and human body fluids.

Highly sensitive voltammetric sensor based on immobilization of bisphosphoramidate-derivative and quantum dots onto multi-walled carbon nanotubes modified gold electrode for the electrocatalytic determination of olanzapine.

In the present paper, a new bisphosphoramidate derivative compound, 1, 4-bis(N-methyl)-benzene-bis(N-phenyl, N-benzoylphosphoramidate) (BMBPBP), was synthesized and used as a mediator for the electrocatalytic oxidation of olanzapine. The electro-oxidation of olanzapine at the surface of the BMBPBP/CdS-quantum dots/multi-walled carbon nanotubes (BMBPBP/CdS-QDs/MWCNTs) modified gold electrode was studied using cyclic voltammetry, chronoamperometry and electrochemical impedance spectroscopy. This sensor showed an excellent electrocatalytic oxidation activity toward olanzapine at less positive potential, pronounced current response, and good sensitivity. The diffusion coefficient and kinetic parameters (such as electron transfer coefficient and the heterogeneous rate constant) were determined for olanzapine oxidation, using the electrochemical approaches. Surface morphology and electrochemical properties of the prepared modified electrode were investigated by scanning electron microscopy (SEM), cyclic voltammetry and electrochemical impedance spectroscopy techniques. The hydrodynamic amperometry at rotating modified electrode at constant potential versus reference electrode was used for detection of olanzapine. Under optimized conditions, the calibration plot was linear in the concentration range of 20 nM to 100 µM and detection limit was found to be 6 nM. The proposed method was successfully applied to the determination of olanzapine in pharmaceuticals and human serum samples.

Application of a Cu-chitosan/multiwalled carbon nanotube film-modified electrode for the sensitive determination of rutin.

A new sensitive electrochemical sensor, a glassy carbon electrode modified with chemically cross-linked copper-complexed chitosan/multiwalled carbon nanotubes (Cu-CS/MWCNT/GCE), for rutin analysis was constructed. Experimental investigations of the influence of several parameters showed that the rutin can effectively accumulate on the surface of the Cu-CS/MWCNT/GCE, which accumulation caused a pair of well-defined redox peaks in the electrochemical signal when measurements were carried out in Britton-Robinson buffer solution (pH 3, 0.04 M). The surface of the Cu-CS/MWCNT/GCE was characterized by field-emission scanning electron microscopy, transmission electron microscopy, and X-ray diffractometry analysis. In a rutin concentration range of 0.05-100 µM and under optimized conditions, a linear relationship between the oxidation peak current of rutin and its concentration was obtained with a detection limit of 0.01 µM. The Cu-CS/MWCNT/GCE showed good selectivity, stability, and reproducibility. Moreover, the sensor was used to determine the presence of rutin in fruits with satisfactory results.

Construction of a sensitive and selective sensor for morphine using chitosan coated Fe3O4 magnetic nanoparticle as a modifier.

A simple and sensitive sensor based on carbon paste electrode (CPE) modified by chitosan-coated magnetic nanoparticle (CMNP) was developed for the electrochemical determination of morphine (MO). The proposed sensor was characterized with scanning electron microscopy (SEM) and electrochemical impedance spectroscopy (EIS). The electrooxidation of MO was studied on modified carbon paste electrode using cyclic voltammetry, chronoamperometry and differential pulse voltammetry as diagnostic techniques. The oxidation peak potential of morphine on the CMNP/CPE appeared at 380 mV which was accompanied with smaller overpotential and increase in oxidation peak current compared to that obtained on the bare carbon paste electrode (CPE). Under optimum conditions the sensor provides two linear DPV responses in the range of 10-2000 nM and 2-720 µM for MO with a detection limit of 3 nM. The proposed sensor was successfully applied for monitoring of MO in serum and urine samples and satisfactory results were obtained.