Electrochemical detection of carbohydrates using copper nanoparticles and carbon nanotubes

Anodized CuO-based reusable non-enzymatic glucose sensor as an alternative method for the analysis of pharmaceutical glucose infusions: a cyclic voltammetric approach

Analyzing pharmaceutical products is a quality control requirement in a production facility. This study presents a CuO electrode-based reusable non-enzymatic sensor as an alternative method for rapid analysis of glucose levels in glucose infusions. CuO is extensively employed as an electrode material in non-enzymatic glucose sensors. Conventionally, these electrodes are fabricated using chemical synthesis of CuO followed by immobilization to the electrode substrate. In contrast, here, Cu metal was mechanically modified to create a grooved surface, followed by electrochemical anodization and subsequent annealing process to grow a seamless CuO layer in situ with enhanced catalytic activity. The morphology of the electrodes was characterized using scanning electron microscopy (SEM) and X-ray diffractometry (XRD). The direct electrocatalytic activity of the developed CuO-modified electrode towards glucose oxidation in alkaline media was investigated by cyclic voltammetry in detail. The CuO-modified electrode commenced the oxidation process around 0.10 V vs. Ag pseudo-reference electrode, demonstrating a significant reduction in the overvoltage for glucose oxidation compared to the bare Cu electrode. The sensor is capable of detecting glucose at low oxidation potentials such as 0.2 V with a sensitivity value of 0.37 µA ppm-1, a wide linear range (80-2300 ppm), limit of quantification (LOQ) of 1 ppm, greater repeatability, 1% precision, 3% bias, a short response time (80 s), good reproducibility and excellent reusability (196 consecutive attempts). The enhanced performance and cost-effectiveness make this sensor a promising alternative method for product analysis in glucose injection solutions.

An electrochemical aptasensor based on multi-walled carbon nanotubes loaded with PtCu nanoparticles as signal label for ultrasensitive detection of adenosine

Adenosine, as an endogenous nucleoside modulator, plays an important role in heart rate regulation, neurotransmission, and control of the respiratory system and thus it is significantly important to realize its sensitive detection. Herein, a highly sensitive electrochemical aptasensor for adenosine detection was proposed by using multi-walled carbon nanotubes (MWCNTs) as support matrix loading PtCu nanoparticles (PtCu-MWCNTs) to amplify signal. On one hand, disposable screen-printing gold electrodes (SPGEs) were used as superb sensing base to ensure the stable connection of aptamers 1 (ssDNA1). On the other hand, the PtCu-MWCNTs complex was synthesized through a one-pot method, which not only can precisely control the proportion of metal mass in the product but also exhibited superior electrocatalytic activity towards H₂O₂. The recognition reactions were achieved by stepwise incubation of ssDNA1, ssDNA2-PtCu-MWCNTs (denoted as ssDNA2-label), and adenosine on the SPGEs. As a result, the constructed electrochemical aptasensor exhibited a wide linear range from 10 nM to 1.0 μM with a low detection limit of 1.0 nM (S/N = 3) for adenosine detection. The aptasensor also successfully realized the adenosine detection in human serum samples, which means that the proposed aptasensor holds a potential application in point-of-care detection.

Ni-Coated Diamond-like Carbon-Modified TiO2 Nanotube Composite Electrode for Electrocatalytic Glucose Oxidation

In this paper, a Ni and diamond-like carbon (DLC)-modified TiO2 nanotube composite electrode was prepared as a glucose sensor using a combination of an anodizing process, electrodeposition, and magnetron sputtering. The composition and morphology of the electrodes were analyzed by a scanning electron microscope and energy dispersive X-ray detector, and the electrochemical glucose oxidation performance of the electrodes was evaluated by cyclic voltammetry and chronoamperometry. The results show that the Ni-coated DLC-modified TiO2 electrode has better electrocatalytic oxidation performance for glucose than pure TiO2 and electrodeposited Ni on a TiO2 electrode, which can be attributed to the synergistic effect between Ni and carbon. The glucose test results indicate a good linear correlation in a glucose concentration range of 0.99–22.97 mM, with a sensitivity of 1063.78 μA·mM−1·cm−2 and a detection limit of 0.53 μM. The results suggest that the obtained Ni-DLC/TiO2 electrode has great application potential in the field of non-enzymatic glucose sensors.

Non-Enzymatic Detection of Glucose in Neutral Solution Using PBS-Treated Electrodeposited Copper-Nickel Electrodes

Transition metals have been explored extensively for non-enzymatic electrochemical detection of glucose. However, to enable glucose oxidation, the majority of reports require highly alkaline electrolytes which can be damaging to the sensors and hazardous to handle. In this work, we developed a non-enzymatic sensor for detection of glucose in near-neutral solution based on copper-nickel electrodes which are electrochemically modified in phosphate-buffered saline (PBS). Nickel and copper were deposited using chronopotentiometry, followed by a two-step annealing process in air (Step 1: at room temperature and Step 2: at 150 °C) and electrochemical stabilization in PBS. Morphology and chemical composition of the electrodes were characterized using scanning electron microscopy and energy-dispersive X-ray spectroscopy. Cyclic voltammetry was used to measure oxidation reaction of glucose in sodium sulfate (100 mM, pH 6.4). The PBS-Cu-Ni working electrodes enabled detection of glucose with a limit of detection (LOD) of 4.2 nM, a dynamic response from 5 nM to 20 mM, and sensitivity of 5.47 ± 0.45 μA cm-2/log10(mole.L-1) at an applied potential of 0.2 V. In addition to the ultralow LOD, the sensors are selective toward glucose in the presence of physiologically relevant concentrations of ascorbic acid and uric acid spiked in artificial saliva. The optimized PBS-Cu-Ni electrodes demonstrate better stability after seven days storage in ambient compared to the Cu-Ni electrodes without PBS treatment.

Facile copper-based nanofibrous matrix for glucose sensing: Eenzymatic vs. non-enzymatic

The current study aims to provide a valid comparison between glucose detection efficiency with an enzymatic and a non-enzymatic sensing platform. A low-cost nano-matrix for glucose sensing was developed by drop-coating copper nanoparticles (Cu NPs) onto a polyacrylonitrile (PAN) electrospun nanofibrous assembly. The PAN NFs/Cu NPs matrix was optimized regarding electrospinning time and Cu NPs content and employed as a non-enzymatic sensor or further modified by cross-linking of glucose oxidase (GOD) for the development of an enzymatic sensor. The non-enzymatic glucose sensor was three times more sensitive (300 mAM^-1cm^-2) than the enzymatic one (81 mAM^-1cm^-2) with similar limit of detection values (5.9 and 5.6 µM, respectively). Incorporation of MWCNTs improved both the LOD (3.3 µM) and the operational stability of the non-enzymatic configuration (RSD 7.3%). The interference effect proved insignificant for the enzymatic sensor due to the innate catalytic selectivity whilst the non-enzymatic sensor acquired selectivity due to the nanofibrous PAN matrix and Nafion coating. The non-enzymatic PAN NFs/Cu NPs sensor was chosen for the detection of glucose in real blood serum samples whilst the PAN NFs/Cu NPs/GOD sensor was applied for glucose detection in fruit juices, both proving recovery results close to 100%.

A Non-Enzymatic Sensor Based on Fc-CHIT/CNT@Cu Nanohybrids for Electrochemical Detection of Glucose

Herein, a composite structure, consisting of Cu nanoparticles (NPs) deposited onto carbon nanotubes and modified with ferrocene-branched chitosan, was prepared in order to develop a nonenzymatic electrochemical glucose biosensor ferrocene-chitosan/carbon nanotube@ Cu (Fc-CHIT/CNT@Cu). The elemental composition of the carbon nanohybrids, morphology and structure were characterized by various techniques. Electrochemical impedance spectroscopy (EIS) was used to study the interfacial properties of the electrodes. Cyclic voltammetry (CV) and chronoamperometry methods in alkaline solution were used to determine glucose biosensing properties. The synergy effect of Cu NPs and Fc on current responses of the developed electrode resulted in good glucose sensitivity, including broad linear detection between 0.2 mM and 22 mM, a low detection limit of 13.52 μM and sensitivity of 1.256 μA mM⁻¹cm⁻². Moreover, the modified electrode possessed long-term stability and good selectivity in the presence of ascorbic acid, dopamine and uric acid. The results indicated that this inexpensive electrode had potential application for non-enzymatic electrochemical glucose detection.

Engineering copper nanoparticles synthesized on the surface of carbon nanotubes for anti-microbial and anti-biofilm applications

Biofilms adhere to surfaces to produce extracellular polymeric substances (EPSs). EPSs grow and protect themselves from external stresses. Their formation causes a foul odor and may lead to chronic infectious diseases in animals and people. Biofilms also inhibit the contact between bacteria and antibiotics, thereby reducing their antibacterial activity. Thus, we describe novel nanostructures, a fusion of copper and multi-walled carbon nanotubes (MWCNTs), which increase antimicrobial activity against biofilms without being toxic to human cells. Simulations based on the stochastic response were performed to predict the efficiency of synthesizing nanostructures. The synthesized Cu/MWCNTs inhibit the growth of Methylobacterium spp., which forms biofilms; antimicrobial testing and cytotoxicity assessments showed that the Cu/MWCNTs were not cytotoxic to human cells. The Cu/MWCNTs come in direct contact with the bacterial cell surface, damage the cell wall, and cause secondary oxidation of reactive oxygen species. Furthermore, the Cu/MWCNTs release copper ions, which inhibit the quorum sensing in Methylobacterium spp., thereby inhibiting the expression of the genes that form biofilms. Additionally, we confirmed excellent electrical and thermal conductivity of Cu/MWCNTs as well as biofilm removal efficiency in the microfluidic channel.

Copper Nanoparticle and Nitrogen Doped Graphite Oxide Based Biosensor for the Sensitive Determination of Glucose

Copper nanoparticles with the diameter of 50 ± 20 nm decorated nitrogen doped graphite oxide (NGO) have been prepared through a simple single step carbonization method using copper metal-organic framework (MOF), [Cu₂(BDC)₂(DABCO)] (where BDC is 1,4-benzenedicarboxylate, and DABCO is 1,4-Diazabicyclo[2.2.2]octane) as precursor. The surface morphology, porosity, surface area and elemental composition of CuNPs/NGO were characterized by various techniques. The as-synthesized CuNPs/NGO nanomaterials were coated on commercially available disposable screen-printed carbon electrode for the sensitive determination of glucose. We find that the modified electrode can detect glucose between 1 μM and 1803 μM (linear range) with good sensitivity (2500 μA mM⁻¹ cm⁻²). Our glucose sensor also possesses low limits of detection (0.44 μM) towards glucose determination. The highly selective nature of the fabricated electrode was clearly visible from the selectivity studies. The practicability of CuNPs/NGO modified electrode has been validated in the human serum samples. The storage stability along with better repeatability and reproducibility results additionally substantiate the superior electrocatalytic activity of our constructed sensor towards glucose.

Khan A, M. Alamshany Z, Gull M, S. Azam E, A. Kosa S, Tahir Soomro M. Synthesis, Electrochemical and Antimicrobial Activity of Colloidal Copper Nanoparticles

ABSTRACT: The colloidal dispersion of copper nanoparticles (CuNPs), prepared by reducing Cu2+ ions using ascorbic acid, was characterized and used for electrochemical and antimicrobial activity investigations. By depositing CuNPs onto the glassy carbon electrode (GCE) surface the CuNPs/GCE was constructed, which was used to study electrochemical behavior of CuNPs and to carry out direct electrochemical detection of trichloroacetic acid (TCA) and 2-chlorophenol (2-CP) in neutral medium. Excellent electrocatalytic ability of CuNPs, assessed by cyclic voltammetry (CV), for the reduction of TCA and 2-CP was detected. The electrochemical impedance analysis (EIS) of the GCE and CuNPs modified GCE evidenced higher charge transfer activity across the modified electrode surface. The antibacterial activity tests of as-synthesized CuNPs on the selected pathogenic strains of pathogenic strains of Salmonella group B (7.9±0.912), Klebsiella pneumonia (8.33±1.561), Escherichia Coli (15.65±1.612), Enterococcus faecalis (5.4±0.612), Staphylococcus aureus (12.6±1.531) and yeast Candida albicans (11.4.3±1.512), respectively, were performed. The results indicated that the use of CuNPs can be pursued as an alternative strategy (to antibiotics) for averting infections by controlling bacterial adhesion and bacterial bio-film formation against microbial infections.

Application of Carbon Nanotubes in Chiral and Achiral Separations of Pharmaceuticals, Biologics and Chemicals

Carbon nanotubes (CNTs) possess unique mechanical, physical, electrical and absorbability properties coupled with their nanometer dimensional scale that renders them extremely valuable for applications in many fields including nanotechnology and chromatographic separation. The aim of this review is to provide an updated overview about the applications of CNTs in chiral and achiral separations of pharmaceuticals, biologics and chemicals. Chiral single-walled carbon nanotubes (SWCNTs) and multi-walled carbon nanotubes (MWCNTs) have been directly applied for the enantioseparation of pharmaceuticals and biologicals by using them as stationary or pseudostationary phases in chromatographic separation techniques such as high-performance liquid chromatography (HPLC), capillary electrophoresis (CE) and gas chromatography (GC). Achiral MWCNTs have been used for achiral separations as efficient sorbent objects in solid-phase extraction techniques of biochemicals and drugs. Achiral SWCNTs have been applied in achiral separation of biological samples. Achiral SWCNTs and MWCNTs have been also successfully used to separate achiral mixtures of pharmaceuticals and chemicals. Collectively, functionalized CNTs have been indirectly applied in separation science by enhancing the enantioseparation of different chiral selectors whereas non-functionalized CNTs have shown efficient capabilities for chiral separations by using techniques such as encapsulation or immobilization in polymer monolithic columns.

Galvanostatic electrodeposition of copper nanoparticles on screen-printed carbon electrodes and their application for reducing sugars determination

In this work, a novel method for the galvanostatic electrodeposition of copper nanoparticles on screen-printed carbon electrodes was developed. Nanoparticles of spherical morphology with sizes between 60 and 280nm were obtained. The electrocatalytic effect of these copper nanospheres towards the oxidation of different sugars was studied. Excellent analytical performance was obtained with the nanostructured sensor: low detection limits and wide linear ranges (1-10,000µM) were achieving for the different reducing sugars evaluated (glucose, fructose, arabinose, galactose, mannose, xylose) with very similar calibration slopes, which demonstrates the possibility of total sugar detection. The reproducibility of these sensors was 4.4% (intra-electrode) and 7.2% (inter-electrode). The stability of the nanostructured electrodes was at least 30 days, even using the same device on different days. Several real samples (honey, orange juice and normal and sugar-free soft drinks) were evaluated to study the reliability of the nanostructured sensor.

Novel synthesis and characterization of pristine Cu nanoparticles for the non-enzymatic glucose biosensor

Non enzymatic electrochemical glucose sensing was developed based on pristine Cu Nanopartilces (NPs)/Glassy Carbon Electrode (GCE) which can be accomplished by simple green method via ocimum tenuiflorum leaf extract. Then, the affect of leaf extract addition on improving Structural, Optical and electrochemical properties of pristine cu NPs was investigated. The synthesized Cu NPs were characterized with X-ray diffraction (X-ray), Uv-Visible spectroscopy (Uv-Vis), Fourier transformation infrared spectroscopy (FTIR), Particle size distribution (PSA), Scanning electron microscopy (SEM), Energy dispersive X-ray spectroscopy (EDS), Transmission electron microscopy (TEM) for structural optical and morphological studies respectively. The synthesized Cu NPs were coated over glassy carbon electrode (GCE) to study the electrochemical response of glucose by cyclic voltammetry and ampherometer. The results indicates that the modified biosensor shows a remarkable sensitivity (1065.21 μA mM^-1 cm^-2), rapid response time (<3s), wide linear range (1 to 7.2 mM), low detection limit (0.038 μM at S/N = 3). Therefore, the prepared Cu NPs by the Novel Bio-mediated route were exploited to construct a non-enzymatic glucose biosensor for sustainable clinical field applications.

Nanostructures: Current uses and future applications in food science

Recent developments in nanoscience and nanotechnology intend novel and innovative applications in the food sector, which is rather recent compared with their use in biomedical and pharmaceutical applications. Nanostructured materials are having applications in various sectors of the food science comprising nanosensors, new packaging materials, and encapsulated food components. Nanostructured systems in food include polymeric nanoparticles, liposomes, nanoemulsions, and microemulsions. These materials enhance solubility, improve bioavailability, facilitate controlled release, and protect bioactive components during manufacture and storage. This review highlights the applications of nanostructured materials for their antimicrobial activity and possible mechanism of action against bacteria, including reactive oxygen species, membrane damage, and release of metal ions. In addition, an overview of nanostructured materials, and their current applications and future perspectives in food science are also presented.

Zinc ion mediated synthesis of cuprous oxide crystals for non-enzymatic glucose detection

Zn²⁺ was used to mediate the fabrication of Cu₂O crystals with different glucose sensing performances depending on their structures.

Combined Blip and Staircase Response of Ascorbic Acid-Stabilized Copper Single Nanoparticle Collision by Electrocatalytic Glucose Oxidation

The current response of the collision of ascorbic acid-stabilized copper (Cu) single nanoparticles (NPs) on a gold (Au) ultramicroelectrode (UME) surface was observed by using an electrocatalytic amplification method. Here, the glucose oxidation electrocatalyzed by oxidized Cu NPs was used as the indicating reaction. In this system, the NP collision signals were obtained simultaneously by both direct particle electrolysis and electrocatalytic amplification. For example, when the applied potential was high enough for Cu NP oxidation, a blip response combined with a staircase response was observed as a current signal. The blip part in the single Cu NP collision signal indicates the self-oxidation of a Cu NP, and the staircase part indicates the steady-state electrocatalytic reaction by oxidized Cu NP.

The in Silico Insight into Carbon Nanotube and Nucleic Acid Bases Interaction

BACKGROUND

To explore practical applications of carbon nanotubes (CNTs) in biomedical fields the properties of their interaction with biomolecules must be revealed. Recent years, the interaction of CNTs with biomolecules is a subject of research interest for practical applications so that previous research explored that CNTs have complementary structure properties with single strand DNA (ssDNA).

OBJECTIVES

Hence, the quantum mechanics (QM) method based on ab initio was used for this purpose. Therefore values of binding energy, charge distribution, electronic energy and other physical properties of interaction were studied for interaction of nucleic acid bases and SCNT.

MATERIALS AND METHODS

In this study, the interaction between nucleic acid bases and a (4, 4) single-walled carbon nanotube (SCNT) were investigated through calculations within quantum mechanics (QM) method at theoretical level of Hartree-Fock (HF) method using 6-31G basis set. Hence, the physical properties such as electronic energy, total dipole moment, charge distributions and binding energy of nucleic acid bases interaction with SCNT were investigated based on HF method.

RESULTS

It has been found that the guanine base adsorption is bound stronger to the outer surface of nanotube in comparison to the other bases, consistent with the recent theoretical studies. In the other words, the results explored that guanine interaction with SCNT has optimum level of electronic energy so that their interaction is stable. Also, the calculations illustrated that SCNT interact to nucleic acid bases by noncovalent interaction because of charge distribution an electrostatic area is created in place of interaction.

CONCLUSIONS

Consequently, small diameter SCNT interaction with nucleic acid bases is noncovalent. Also, the results revealed that small diameter SCNT interaction especially SCNT (4, 4) with nucleic acid bases can be useful in practical application area of biomedical fields such detection and drug delivery.

Synthesis of CuNP-Modified Carbon Electrodes Obtained by Pyrolysis of Paper

A one-step approach for the synthesis and integration of copper nanoparticles (CuNPs) onto paper-based carbon electrodes is herein reported. The method is based on the pyrolysis (1000 °C under a mixture of 95% Ar / 5% H₂ for 1 hour) of paper strips modified with a saturated solution of CuSO₄ and yields to the formation of abundant CuNPs on the surface of carbonized cellulose fibers. The resulting substrates were characterized by a combination of scanning electron microscopy, EDX, Raman spectroscopy as well as electrical and electrochemical techniques. Their potential application, as working electrodes for nonenzymatic amperometric determination of glucose, was then demonstrated (linear response up to 3 mM and a sensitivity of 460 ± 8 μA·cm^-2·mM^-1). Besides being a simple and inexpensive process for the development of electrochemically-active substrates, this approach opens new possibilities for the in-situ synthesis of metallic nanoparticles without the traditional requirements of solutions and adjuvants.

Facile preparation of a highly sensitive nonenzymatic glucose sensor based on multi-walled carbon nanotubes decorated with electrodeposited metals

Preparation of Ni/CuAg/MWCNT hybrid composite modified electrode: (a) bare, (b) MWCNT, (c) CuAg/MWCNT, and (d) Ni/CuAg/MWCNT modified electrodes.

Graphene oxide doped poly(3,4-ethylenedioxythiophene) modified with copper nanoparticles for high performance nonenzymatic sensing of glucose

A highly sensitive and stable nonenzymatic glucose sensor was developed through the electrochemical deposition of Cu nanoparticles onto an electrodeposited nanocomposite of conducting polymer PEDOT doped with graphene oxide.