Magnetite graphene oxide-albumin conjugate: carrier for the imatinib anticancer drug.

Carbon nanomaterials are widely used in biomedical applications due to their versatile properties. These are the attractive candidates for the carrying of anticancer drugs, genes, and proteins for chemotherapy. Imatinib is an effective chemotherapy drug whose toxicity has created a significant limitation in treatment. In this research, a new biocompatible nanocarrier based on albumin-magnetite graphene oxide conjugates was reported for the loading and release of imatinib. The magnetite graphene oxide nanocomposite was investigated by ultra violet-visible spectroscopy (UV-Vis), field emission scanning electron microscope (FE-SEM), X-ray diffraction spectroscopy (XRD) and energy diepersive X-ray spectroscopy (EDX) methods. The crystallite size of Fe3O4 nanoparticles on graphene oxide obtained from XRD is about 14 nm which is in agreement well with the SEM results. We show that magnetite graphene oxide conjugated with albumin is an extremely efficient carrier. An efficient loading of IM, 81% at pH 7.0, time 2 h and initial concentration of 1 mg/mL was seen onto magnetite graphene oxide-albumin in comparison to graphene oxide and magnetite graphene oxide due to the presence of oxygen and nitrogen functional groups of albumin. Upon the pH 9.0 and 7.0, 7% and 16% imatinib could be released from the magnetite graphene oxide-albumin in a time span of 5 h but when exposed pH 4.0 the corresponding 31% was released in 5 h. After 20 h, 21, 42 and 68% of imatinib was released at pH 9.0, 7.0 and 4.0, respectively. This illustrates the major benefits of the developed approach for biomedical applications.

Graphene-modified electrodes for sensing doxorubicin hydrochloride in human plasma.

Doxorubicin (DOX), an anthracycline molecule, is currently one of the most widely used anticancer drugs in clinics. Systematic treatment of patients with DOX is known to be accompanied by several unpleasant side effects due to the toxicity of the drug. Thus, monitoring of DOX concentration in serum samples has become increasingly important to avoid side effects and ensure therapeutic efficiency. In this study, we discuss the construction of a disposable electrochemical sensor for the direct monitoring of DOX in clinical blood samples. The sensor is based on coating a gold electrode in a flexible integrated electrode construct formed on polyimide sheets using photolithography, with nitrogen-doped reduced graphene oxide (N-rGO) suspended in chitosan. Under optimized conditions, a linear relationship between the oxidative peak current and the concentration of DOX in the range of 0.010-15 µM with a detection limit of 10 nM could be achieved. The sensor was adapted to monitor DOX in serum samples of patients under anticancer treatment. Graphical abstract.

Dopamine-functionalized cyclodextrins: modification of reduced graphene oxide based electrodes and sensing of folic acid in human serum.

A mandatory step in any sensor fabrication is the introduction of analyte-specific recognition elements to the transducer surface. In this study, the possibility to anchor ß-cyclodextrin-modified dopamine to a reduced graphene oxide based electrochemical transducer for the sensitive and selective sensing of folic acid is demonstrated. The sensor displays good electrocatalytic activity toward the oxidation of folic acid. The strong affinity of the surface-confined ß-cyclodextrin for folic acid, together with favorable electron transfer characteristics, resulted in a sensor with a detection limit of 1 nM for folic acid and a linear response up to 10 µM. Testing of the sensor on serum samples from healthy individuals and patients diagnosed with folic acid deficiency validated the sensing capability. Graphical abstract.

Direct and mediated electrochemistry of peroxidase and its electrocatalysis on a variety of screen-printed carbon electrodes: amperometric hydrogen peroxide and phenols biosensor.

This study compares the behaviour of direct and mediated electrochemistry of horseradish peroxidase (HRP) immobilised on screen-printed carbon electrodes (SPCEs), screen-printed carbon electrodes modified with carboxyl-functionalised multi-wall carbon nanotubes (MWCNT-SPCEs) and screen-printed carbon electrodes modified with carboxyl-functionalised single-wall carbon nanotubes (SWCNT-SPCEs). The techniques of cyclic voltammetry and amperometry in the flow mode were used to characterise the properties of the HRP immobilised on screen-printed electrodes. From measurements of the mediated and mediatorless currents of hydrogen peroxide reduction at the HRP-modified electrodes, it was concluded that the fraction of enzyme molecules in direct electron transfer (DET) contact with the electrode varies substantially for the different electrodes. It was observed that the screen-printed carbon electrodes modified with carbon nanotubes (MWCNT-SPCEs and SWCNT-SPCEs) demonstrated a substantially higher percentage (≈100 %) of HRP molecules in DET contact than the screen-printed carbon electrodes (≈60 %). The HRP-modified electrodes were used for determination of hydrogen peroxide in mediatorless mode. The SWCNT-SPCE gave the lowest detection limit (0.40 ± 0.09 µM) followed by MWCNT-SPCE (0.48 ± 0.07 µM) and SPCE (0.98 ± 0.2 µM). These modified electrodes were additionally developed for amperometric determination of phenolic compounds. It was found that the SWCNT-SPCE gave a detection limit for catechol of 110.2 ± 3.6 nM, dopamine of 640.2 ± 9.2 nM, octopamine of 3341 ± 15 nM, pyrogallol of 50.10 ± 2.9 nM and 3,4-dihydroxy-L-phenylalanine of 980.7 ± 8.7 nM using 50 µM H2O2 in the flow carrier.

Cu-Co Bimetallic Catalyst-based Electrochemical Sensing Platform for Determination of Bisoprolol in Clinical Samples.

BACKGROUND: Bisoprolol (BIS) is a selective beta-blocker. It has been successfully used to treat hypertension and angina pectoris. An overdose of BIS can lead to serious complications. An overdose is a medical emergency that requires immediate medical attention to overcome the adverse effects of the overdose. Hence, sensitive, reliable, and cost-effective methods are required for the determination of BIS. METHODS: In this work, a new electrochemical sensing platform based on a bimetallic catalyst was developed for the determination of BIS. The Cu-Co nanocatalyst was easily synthesized by galvanic displacement onto a carbon paste electrode (CPE). Then, field emission scanning electron microscopy (FESEM), energy dispersive spectroscopy (EDS), and cyclic voltammetry (CV) were utilized for the characterization of the Cu-Co catalyst. RESULTS: The galvanic displacement of Cu metal significantly affected the electro-catalytic behavior of the Cu-Co catalyst and the Cu-Co/CPE electrode displayed a very sensitive and accurate response towards BIS. Under optimized conditions, the response was linear in the 3 to 120 µM concentration range, sensitivity of 631.1 µA mM-1 and a detection limit of as low as 0.4 µM using cyclic voltammetry. The simple proposed method was also successfully employed in the analysis of BIS in biological and pharmaceutical samples. The advantages of Cu-Co/CPE are its fast and simple manufacturing and the possibility of a repeated surface regeneration of the sensing platform, as well as its application for the detection of BIS in tablets and biological samples, making Cu-Co significant promise for use in clinical diagnostics. Besides, the synthesized catalysts showed excellent reusability and stability. CONCLUSION: The presence of Cu metal due to galvanic displacement increased the sensitivity. These findings suggest that the new nanocatalyst has potential applications in sensors and electronics.

Conjugation of Doxorubicin and Carbon-based-nanostructures for Drug Delivery Against HT-29 Colon Cancer Cells.

BACKGROUND: A drug delivery system is the method or process of administering a pharmaceutical compound to achieve a therapeutic effect in humans or animals. Such systems release the drugs at specific amounts in a specific site. The carbon based-nanomaterials have been actively used as drug carriers to treat various cancer. OBJECTIVE: This study aimed to evaluate the cytotoxic effects of DOX-GO, DOX-OMC and DOX-CNT in colon cancer cells (HT29). METHODS: We reported platforms based on graphene oxide (GO), ordered mesoporous carbon (OMC) and carbon nanotubes (CNT) to conjugate with doxorubicin (DOX). The conjugation of DOX with carbon nanomaterial was investigated by UV-Vis spectroscopy, field emission scanning electron microscope (FE-SEM) and cyclic voltammetry (CV) methods. RESULTS: We showed that graphene oxide was a highly efficient matrix. Efficient loading of DOX, 89%, 78%, and 73.5% at pH 7.0 was seen onto GO, OMC and CNT, respectively. Upon pH 4. 0 after 15 h, 69%, 61% and 61% of DOX could be released from the DOX-GO, DOX-OMC and DOX-CNT, respectively, which illustrated the significant benefits of the developed approach for carbon nanomaterial applications. In vitro cytotoxicity analysis showed greater cytotoxicity of DOX/GO, DOX/OMC and DOX/CNT in comparison with GO, OMC and CNT against HT29 colon cancer cells with cell viability of 22%, 40% and 44% after 48 h for DOX-GO, DOX-OMC and DOX-CNT, respectively. CONCLUSION: The nanohybrids based on DOX-carbon nanomaterial, because of their unique physical and chemical properties, will remarkably enhance the anti-cancer activity.

Application of graphene oxide in the adsorption and extraction of bioactive compounds from lemon peel.

The bioactive compounds like rutin, naringin, and gallic acid have been separated from lemon peel by graphene oxide (GO). The different influences such as pH values and separation conditions were investigated. Moreover, the samples were characterized by Fourier transform infrared spectroscopy, thermogravimetric analysis, scanning electron microscopy, UV-Vis spectroscopy, and high-performance liquid chromatography. The findings of high-performance liquid chromatography revealed that the adsorbed proportion of rutin by GO was more than naringin and gallic acid so that 66.7% of rutin, 34% of naringin, and 19% of gallic acid from the extract were remarkably adsorbed and separated. Besides, adsorption percentage of these materials by GO was considered 74.8% after five cycles of adsorption-desorption process. On the other hand, we carried out batch experiments in order to study the adsorption mechanism of rutin on the GO since rutin was the highest quantity of bioactive substance in lemon peel. Pseudo-second-order kinetic model and Langmuir isotherm were the best models for describing adsorption process of rutin by GO. Adsorption capacity of rutin by GO was obtained about 21.08 mgg-1. In addition, the physical adsorption of rutin by GO was confirmed by Dubinin-Radushkevich isotherm. This research confirmed that this method for separation of flavonoids is simple and less cost.

Colorimetric assay based on horseradish peroxidase/reduced graphene oxide hybrid for sensitive detection of hydrogen peroxide in beverages.

We reported a simple and sensitive colorimetric assay for detection of hydrogen peroxide (H2O2) based on the oxidation of 2,2׳-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) by UV-Vis spectroscopy method. The reduced graphene oxide (rGO) was prepared using green tea extract as bio-reducing and stabilizer agent and decorated by horseradish peroxidase (HRP). The surface of Au interface was modified with HRP-rGO hybrid. The formation of HRP-rGO hybrid was confirmed by cyclic voltammetry, scanning electron microscopy (SEM), energy-dispersive X-ray Spectroscopy (EDX) and Raman spectroscopy·H2O2 can be catalysed by HRP-rGO hybrid and converted into water and oxygen. The ABTS substrate takes up oxygen to form a green coloured product that has absorption peaks at 421, 655 nm and 737 nm. The colour development is linearly dependent on HRP in the range of 4-50 µg/L. The color of the green product solution is stable for 20 min. The absorption intensity is strongly related to the hydrogen peroxide concentration. The absorption intensity of the formed product scaled linearly with the hydrogen peroxide concentration in the ranges of 0.3-20 µM and 20-8000 µM with a detection limit of ≈15 nM could be achieved. The biosensor with excellent limit detection and wide linear ranges was adapted to monitor H2O2 in different beverages.

Direct electrochemistry and bioelectrocatalysis of a class II non-symbiotic plant haemoglobin immobilised on screen-printed carbon electrodes.

In this study, direct electron transfer (ET) has been achieved between an immobilised non-symbiotic plant haemoglobin class II from Beta vulgaris (nsBvHb2) and three different screen-printed carbon electrodes based on graphite (SPCE), multi-walled carbon nanotubes (MWCNT-SPCE), and single-walled carbon nanotubes (SWCNT-SPCE) without the aid of any electron mediator. The nsBvHb2 modified electrodes were studied with cyclic voltammetry (CV) and also when placed in a wall-jet flow through cell for their electrocatalytic properties for reduction of H(2)O(2). The immobilised nsBvHb2 displayed a couple of stable and well-defined redox peaks with a formal potential (E°') of -33.5 mV (vs. Ag|AgCl|3 M KCl) at pH 7.4. The ET rate constant of nsBvHb2, k(s), was also determined at the surface of the three types of electrodes in phosphate buffer solution pH 7.4, and was found to be 0.50 s(-1) on SPCE, 2.78 s(-1) on MWCNT-SPCE and 4.06 s(-1) on SWCNT-SPCE, respectively. The average surface coverage of electrochemically active nsBvHb2 immobilised on the SPCEs, MWCNT-SPCEs and SWCNT-SPCEs obtained was 2.85 × 10(-10) mol cm(-2), 4.13 × 10(-10) mol cm(-2) and 5.20 × 10(-10) mol cm(-2). During the experiments the immobilised nsBvHb2 was stable and kept its electrochemical and catalytic activities. The nsBvHb2 modified electrodes also displayed an excellent response to the reduction of hydrogen peroxide (H(2)O(2)) with a linear detection range from 1 µM to 1000 µM on the surface of SPCEs, from 0.5 µM to 1000 µM on MWCNT-SPCEs, and from 0.1 µM to 1000 µM on SWCNT-SPCEs. The lower limit of detection was 0.8 µM, 0.4 µM and 0.1 µM at 3σ at the SPCEs, the MWCNT-SPCEs, and the SWCNT-SPCEs, respectively, and the apparent Michaelis-Menten constant, K(M)(app), for the H(2)O(2) sensors was estimated to be 0.32 mM , 0.29 mM and 0.27 mM, respectively.

Electrochemical sensor based on magnetite graphene oxide/ordered mesoporous carbon hybrid to detection of allopurinol in clinical samples.

Allopurinol (ALO) is a radical scavenging clinical drug, a drug in the treatment of gout, an inhibitor of xanthine oxidase and an effective agent for anti-cancer purposes. The xanthine oxidase is thus essential, and the amount of ALO needs to be controlled more strictly. In this study, a new electrochemical sensor based on magnetite graphene oxide/ordered mesoporous carbon (Fe3O4@GO/OMC) hybrid was prepared and characterized. The results showed sphere shape Fe3O4 nanoparticles with a diameter in the range 17-22 nm on composite. Modification of carbon paste electrode (CPE) with Fe3O4@GO/OMC (Fe3O4@GO/OMC-CPE) allowed the ultrasensitive and selective detection of ALO at oxidation potential of 1.05 V with linear range of 0.05-7 µmol L-1, limit of detection of 47 nmol L-1 and sensitivity of 708 µA mmol-1 L. Also, the results demonstrate that charge transfer at the interface of Fe3O4@GO/OMC hybrid can provide a synergistic effect in comparison with Fe3O4@GO and OMC. The unique surface chemistry of Fe3O4@GO/OMC interface allows π-π stacking and electrostatic interactions with ALO. The advantages are the possibility to regenerate the surface of the sensor, its rapid and easy of production, as well as its applicability for detection of ALO in Tablets and human serum samples, making Fe3O4@GO/OMC-CPE promising interface for bio-electrochemical applications.

Green tea extract assisted green synthesis of reduced graphene oxide: Application for highly sensitive electrochemical detection of sunset yellow in food products.

The search to find simple, cost-effective, environmentally friendly method for synthesising of reduced graphene oxide (rGO) has motivated the use of various natural materials. Also, monitoring of sunset yellow (SY) level in foods due to the potential negative side effects is imperative. In this study, tea extract was explored as reducing and stabilizing agent for synthesising of rGO. The rGO modified carbon paste electrode (rGO/CPE) was used as a highly sensitive electrochemical sensor for the detection of SY. The rGO/CPE, due to the large surface area, showed strong enhancement effect on electrochemical oxidation of SY. Under optimized conditions, linear range between 0.05 and 10 µM with a detection limit of 27 nM could be achieved. The proposed sensor was used to determine the amount of SY in food products with satisfactory results, and the results were in good agreement with the results obtained by UV-Vis spectroscopy.

MoS2/reduced graphene oxide nanocomposite for sensitive sensing of cysteamine in presence of uric acid in human plasma.

A hybrid nanocomposite of MoS2 nanosheets and reduced graphene oxide (rGO) was fabricated by a facile and effective method. The morphology and structure of the nanocomposite (MoS2-rGO) were characterized by scanning electron microscopy, X-ray photoelectron spectroscopy, Raman spectroscopy, electrochemical impedance spectroscopy and cyclic voltammetry. The MoS2 nanosheets were uniformly anchored on the rGO framework with strong adhesion. A glassy carbon electrode modified by drop-casting with MoS2-rGO was used for the electrochemical oxidation of cysteamine (CA) in the presence of uric acid (UA). Under optimum conditions, the anodic peak current of CA shows a linear relation with the CA concentration between 0.01 and 20µM with a detection limit of 7nM. The proposed electrochemical sensor was used for determination of CA in human plasma.

A sensitive voltammetric detection of pramipexole based on 1,1,3,3-tetramethyldisilazanecarbon nanotube modified electrode.

A simple low-cost method is proposed to fabricate a functionalized multi-wall carbon nanotube (MWCNT) with 1,1,3,3-tetramethyldisilazane (TMDS) molecule. The techniques of scanning electron microscope (SEM) with electron diffraction and energy dispersive X-ray (EDAX) analysis were applied to characterize the functionalized TMDS-MWCNT. The results showed that a MWCNT with high functionalization of TMDS can be obtained using this simple method. A new nanostructure sensor was constructed based on a glassy carbon electrode modified with TMDS-MWCNT (TMDS-MWCNT/GCE). It was found that the TMDS-MWCNT/GCE exhibits good catalytic activity toward oxidation of pramipexole (PPX) drug, leading to a concentration range of 0.8 to 600µM with a detection limit of 0.2µM at 3σ using the differential pulse voltammetry technique, a sensitivity of 0.084µAµM-1, and a correlation coefficient of 0.991. Furthermore, the TMDS-MWCNT/GCE was used for PPX detection in tablets and human blood serum samples. The method showed no interference from tablet excipients; hence, it can be useful and fit for the quantification of PPX in bulk and tablet dosage forms. The proposed method was validated successfully as applied to the quantification of the drug in tablet dosage forms. The accuracy of detection results using the proposed method was evaluated as excellent comparing with those obtained by the reference method.

On demand electrochemical release of drugs from porous reduced graphene oxide modified flexible electrodes.

Despite the advantages of an electrochemical control for drug release, only a handful of electrochemical-based release systems have been developed so far. We report herein on the development of an electrochemically activatable platform for on-demand delivery of drugs. It is based on flexible gold thin film electrodes coated with porous reduced graphene oxide (prGO) nanosheets onto which the drug of interest has been integrated beforehand. Two different drugs are investigated here: ondansetron hydrochloride (ODS), a selective 5-HT3 receptor antagonist used for preventing nausea and vomiting caused by chemotherapy and radiotherapy, and ampicillin (AMP), an antibiotic to prevent and treat a number of bacterial infections such as respiratory tract infections, urinary tract infections, and meningitis. In the case of ODS, application of a negative potential bias of -0.8 V results in a sustained slow ODS release with an ODS flux of 47 µg cm-2 h-1. In the case of AMP, we show that polyethyleneimine modified prGO (prGO/PEI) is an extremely efficient matrix. Upon the application of +0.8 V, 24% of AMP could be released from the electrical interface in a time span of 2 h. The released AMP kept its antibacterial activity as demonstrated by antimicrobial tests. These examples illustrate the major benefits of the developed approach for biomedical applications.

The interaction between ketamine and some crown ethers in common organic solvents studied by NMR: the effect of donating atoms and ligand structure.

1H NMR spectroscopy was used to investigate the stoichiometry and stability of the drug ketamine cation complexes with some crown ethers, such as 15-crown-5 (15C5), aza-15-crown-5 (A15C5), 18-crown-6 (18C6), aza-18-crown-6 (A18C6), diaza-18-crown-6 (DA18C6), dibenzyl-diaza-18-crown-6 (DBzDA18C6) and cryptant [2,2,2] (C222) in acetonitrile (AN), dimethylsulfoxide (DMSO) and methanol (MeOH) at 27 degrees C. In order to evaluate the formation constants of the ketamine cation complexes, the CH3 protons chemical shift (on the nitrogen atom of ketamine) was measured as function of ligand/ketamine mole ratio. The formation constant of resulting complexes were calculated by the computer fitting of chemical shift versus mole ratio data to appropriate equations. A significant chemical shift variation was not observed for 15C5 and 18C6. The stoichiometry of the mono aza and diaza ligands are 1:1 and 1:2 (ligand/ketamine), respectively. In all of the solvents studied, DA18C6 formed more stable complexes than other ligands. The solvent effect on the stability of these complexes is discussed.

The ultrasound-assisted aqueous extraction of rice bran oil.

In this work, aqueous extraction of rice bran oil was done without and with ultrasound pretreatment. Key factors controlling the extraction and optimal operating conditions were identified. The highest extraction efficiency was found at pH=12, temperature of 45°C, agitation speed of 800rpm and agitation time of 15min, ultrasound treatment time of 70min and ultrasound treatment temperature of 25°C. Moreover, extraction yields were compared to ultrasound-assisted aqueous extraction and Soxhlet extraction. The results showed that the yield of rice bran oil at ultrasound-assisted aqueous extraction was close to the yield of oil extracted by hexane Soxhlet extraction. This result implied that the yield of rice bran oil was significantly influenced by ultrasound. With regard to quality, the oil extracted by ultrasound-assisted aqueous process had a lower content of free fatty acid and lower color imparting components than the hexane-extracted oil. Also, effect of parboiling of paddy on hexane and ultrasound-assisted aqueous extraction was studied. Both extraction methods gives higher percentage of oil from par boiled rice bran compared with raw rice bran. This may be due to the fact that parboiling releases the oil.

MoS2/reduced graphene oxide as active hybrid material for the electrochemical detection of folic acid in human serum.

In this study, a new matrix based on a molybdenum disulfide-reduced graphene oxide hybrid (MoS2-rGO) was prepared and characterized. Modification of a glassy carbon electrode (GCE) with MoS2-rGO (MG) using drop casting allowed for the selective analysis of folic acid in the presence of a variety of interference species with a limit of detection of 10nM, a linear range between 0.01µM and 100µM with a sensitivity of 14µAµM(-1). In addition, the analytical performance of the proposed sensor was successfully conducted for the determination of folic acid in human serum samples, making MG-GC electrodes promising interfaces for bio-electrochemical applications.