Search results for: modified gold nanoparticles electrode

Authors: Mohsen Adabi, Mahdi Adabi, Reza Saber

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The recent advancements in nanomaterials have provided a platform to develop efficient transduction matrices for sensors. Modified electrodes allow to electrochemists to enhance the property of electrode surface and provide desired properties such as improved sensing capabilities, higher electron transfer rate and prevention of undesirable reactions competing kinetically with desired electrode process. Nanostructured electrodes including arrays of carbon nanotubes have demonstrated great potential for the development of electrochemical sensors and biosensors. The aim of this work is to evaluate the concentration of multi-walled carbon nanotubes (MWCNTs) on the conductivity of gold electrode. For this work, raw MWCNTs was functionalized and shortened. Raw and shorten MWCNTs were characterized using transfer electron microscopy (TEM). Next, 0.5, 2 and 3.5 mg of Shortened and functionalized MWCNTs were dispersed in 2 mL Dimethyl formamide (DMF) and cysteamine modified gold electrodes were incubated in the different concentrations of MWCNTs for 8 hours. Then, the immobilization of MWCNTs on cysteamine modified gold electrode was characterized by scanning electron microscopy (SEM) and the effect of MWCNT concentrations on electron transfer of modified electrodes was investigated by cyclic voltammetry (CV). The results demonstrated that CV response of ferricyanide redox at modified gold electrodes increased as concentration of MWCNTs enhanced from 0.5 to 2 mg in 2 mL DMF. This increase can be attributed to the number of MWCNTs which enhance on the surface of cysteamine modified gold electrode as the MWCNTs concentration increased whereas CV response of ferricyanide redox at modified gold electrodes did not changed significantly as the MWCNTs concentration increased from 2 to 3.5 mg in 2 mL DMF. The reason may be that amine groups of cysteamine modified gold electrodes are limited to a given number which can interact with the given number of carboxylic groups of MWCNTs and CV response of ferricyanide redox at modified gold do not enhance after amine groups of cysteamine are saturated with carboxylic groups of MWCNTs.

Keywords: carbon nanotube, cysteamine, electrochemical sensor, gold electrode

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Authors: Fatima Ammari, Meriem Chenouf

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Synthesis of gold nanoparticles (AuNPs) has attracted much attention since the pioneering discovery of the high catalytic activity of supported gold nanoparticles in the reaction of CO oxidation at low temperature. In this research field, we used montmorillonite pre-acidified under gentle conditions for AuNPs stabilization; using different loading percentage 1, 2 and 5%. The gold nanoparticles were obtained using chemical reduction method using NaBH4 as reductant agent. The obtained gold nanoparticles stabilized in acid-activated montmorillonite were used as catalysts for reduction of 4-nitrophenol to aminophenol with sodium borohydride at room temperature The UV-Vis results confirm directly the gold nanaoparticles formation. The XRD N2 adsorption and MET results showed the formation of gold nanoparticles in the pores of preacidified montmorillonite with an average size of 5.7nm. The reduction reaction of 4-nitrophenol into 4-aminophenol with NaBH4 catalyzed by Au°-montmorillonite catalyst exhibits remarkably a high activity; the reaction was completed within 4.5min.

Keywords: gold, acid-activated montmorillonite, nanoparticles, 4-nitrophenol

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Authors: Fatma Gülden Şi̇mşek, Osman Meli̇h Can, Mehmet Yumak, Bora Gari̇pcan, Yekta Ülgen

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In this study, the impedance spectroscopy is used as a detection tool in order to characterize surface coating with graphene oxide. Gold electrodes are produced by standard lithography procedures and then coated with graphene oxide using self-assembly method. The impedance of redox solution through bare gold electrodes and graphene oxide coated gold electrodes is measured in the low and high frequency range. The graphene oxide coating reduces the impedance value of the gold electrode and this reduction is distinguishable in the low-frequency range.

Keywords: bioimpedance, electrode characterization, graphene oxide, gold electrodes, impedance spectroscopy

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Authors: M. S. Kilic, S. Korkut, B. Hazer

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Newly synthesized Polypropylene-g-Polyethylene glycol polymer was first time used for a compartment-less enzymatic fuel cell. Working electrodes based on Polypropylene-g-Polyethylene glycol were operated as unmediated and mediated system (with ferrocene and gold/cobalt oxide nanoparticles). Glucose oxidase and bilirubin oxidase was selected as anodic and cathodic enzyme, respectively. Glucose was used as fuel in a single-compartment and membrane-less cell. Maximum power density was obtained as 0.65 nW cm-2, 65 nW cm-2, and 23500 nW cm-2 from the unmediated, ferrocene and gold/cobalt oxide modified polymeric film, respectively. Power density was calculated to be ~16000 nW cm-2 for undiluted wastewater sample with gold/cobalt oxide nanoparticles including system.

Keywords: bilirubin oxidase, enzymatic fuel cell, glucose oxidase, nanoparticles

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Authors: Stephen Daniel Iduh, Evans Chidi Egwin, Oluwatosin Kudirat Shittu

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The process for the development of reliable and eco-friendly metallic Nanoparticles is an important step in the field of Nanotechnology for biomedical application. To achieve this, use of natural sources like biological systems becomes essential. In the present work, extracellular biosynthesis of gold Nanoparticles using aqueous leave and stembark extracts of K. senegalensis has been attempted. The gold Nanoparticles produced were characterized using High Resolution scanning electron microscopy, Ultra Violet–Visible spectroscopy, zeta-sizer Nano, Energy-Dispersive X-ray (EDAX) Spectroscopy and Fourier Transmission Infrared (FTIR) Spectroscopy. The cytotoxicity of the synthesized gold nanoparticles on MCF-7 cell line was evaluated using MTT assay. The result showed a rapid development of Nano size and shaped particles within 5 minutes of reaction with Surface Plasmon Resonance at 520 and 525nm respectively. An average particle size of 20-90nm was confirmed. The amount of the extracts determines the core size of the AuNPs. The core size of the AuNPs decreases as the amount of extract increases and it causes the shift of Surface Plasmon Resonance band. The FTIR confirms the presence of biomolecules serving as reducing and capping agents on the synthesised gold nanoparticles. The MTT assay shows a significant effect of gold nanoparticles which is concentration dependent. This environment-friendly method of biological gold Nanoparticle synthesis has the potential and can be directly applied in cancer therapy.

Keywords: biosynthesis, gold nanoparticles, characterization, calotropis procera, cytotoxicity

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Authors: Ahmad Shanei, Mohammad Mahdi Shanei

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When a liquid is irradiated with high intensities (> 1 W) and low frequencies (≤ 1 MHz) ultrasound, acoustic cavitation occurs. Acoustic cavitation generates free radicals from the breakdown of water and other molecules. The existence of particles in liquid provide nucleation sites for cavitation bubbles and lead to decrease the ultrasonic intensity threshold needed for cavitation onset. The study was designed to measure hydroxyl radicals in terephthalic acid solutions containing 30 nm gold nanoparticles in a near field of a 1 MHz sonotherapy probe. The effect of ultrasound irradiation parameters containing mode of sonication and ultrasound intensity in hydroxyl radicals production have been investigated by the spectrofluorometry method. Recorded fluorescence signal in terephthalic acid solution containing gold nanoparticles was higher than the terephthalic acid solution without gold nanoparticles. Also, the results showed that any increase in intensity of the sonication would be associated with an increase in the fluorescence intensity. Acoustic cavitation in the presence of gold nanoparticles has been introduced as a way for improving therapeutic effects on the tumors. Also, the terephthalic acid dosimetry is suitable for detecting and quantifying free hydroxyl radicals as a criterion of cavitation production over a range of condition in medical ultrasound fields.

Keywords: acoustic cavitation, gold nanoparticle, chemical dosimetry, terephthalic acid

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Authors: Indu Barwal, Shloka Thakur, Subhash C. Yadav

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The plant virus capsid protein based nanoparticles are extensively studied for their application in biomedical research for development of nanomedicines and drug delivery systems. We have developed a chimeric drug delivery system by controlled in vitro assembly of separately bioconjugated fluorescent dye (as reporting molecule), folic acid (as receptor binding biomolecule for targeted delivery) and doxorubicin (as anticancer drug) using modified EDC NHS chemistry on heterologously overexpressed (E. coli) capsid proteins of cowpea chlorotic mottle virus (CCMV). This chimeric vehicle was further encapsidated on gold nanoparticles (20nm) coated with 5≠ thiolated DNA probe to neutralize the positive charge of capsid proteins. This facilitates the in vitro assembly of modified capsid subunits on the gold nanoparticles to develop chimeric GNPs encapsidated targeted drug delivery system. The bioconjugation of functionalities, number of functionality on capsid subunits as well as virus like nanoparticles, structural stability and in vitro assembly were confirmed by SDS PAGE, relative absorbance, MALDI TOF, ESI-MS, Circular dichroism, intrinsic tryptophan fluorescence, zeta particle size analyzer and TEM imaging. This vehicle was stable at pH 4.0 to 8.0 suitable for many organelles targeting. This in vitro assembled chimeric plant virus like particles could be suitable for ideal drug delivery vehicles for subcutaneous cancer treatment and could be further modified for other type of cancer treatment by conjugating other functionalities (targeting, drug) on capsids.

Keywords: chimeric drug delivery vehicles, bioconjugated plant, virus, capsid

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Authors: Anahita Izadyar, My Ni Van, Kayleigh Amber Rodriguez, Ilwoo Seok, Elizabeth E. Hood

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Using a recombinant enzyme derived from corn and a simple modification, we fabricated a facile, fast, and cost-beneficial biosensor to measure glucose. The Nafion/ Plant Produced Mn Peroxidase (PPMP)– glucose oxidase (GOx)- Bovine serum albumin (BSA) /Au electrode showed an excellent amperometric response to detect glucose. This biosensor is capable of responding to a wide range of glucose—20.0 µM−15.0 mM and has a lower detection limit (LOD) of 2.90µM. The reproducibility response using six electrodes is also very substantial and indicates the high capability of this biosensor to detect a wide range of 3.10±0.19µM to 13.2±1.8 mM glucose concentration. Selectivity of this electrode was investigated in an optimized experimental solution contains 10% diet green tea with citrus containing ascorbic acid (AA), and citric acid (CA) in a wide concentration of glucose at 0.02 to 14.0mM with an LOD of 3.10µM. Reproducibility was also investigated using 4 electrodes in this sample and shows notable results in the wide concentration range of 3.35±0.45µM to of 13.0 ± 0.81 mM. We also used other voltammetry methods to evaluate this biosensor. We applied linear sweep voltammetry (LSV) and this technique shows a wide range of 0.10−15.0 mM to detect glucose with a lower detection limit of 19.5µM. The performance and strength of this enzyme biosensor were the simplicity, wide linear ranges, sensitivities, selectivity, and low limits of detection. We expect that the modified biosensor has the potential for monitoring various biofluids.

Keywords: plant-produced manganese peroxidase, enzyme-based biosensors, glucose, modified gold electrode, glucose oxidase

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Authors: Alex Soares Castro, Matheus Manoel Teles de Menezes, Larissa Silva de Azevedo, Ana Carolina Caleffi Patelli, Osmair Vital de Oliveira, Aline Thais Bruni, Marcelo Firmino de Oliveira

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Considering the problem of the seizure of illicit drugs, as well as the development of electrochemical sensors using chemically modified electrodes, this work shows the study of the electrochemical activity of cocaine in carbon paste electrode chemically modified with Cu (II) trans 3-MeO salcn complex. In this context, cyclic voltammetry was performed on 0.1 mol.L⁻¹ KCl supporting electrolyte at a scan speed of 100 mV s⁻¹, using an electrochemical cell composed of three electrodes: Ag /AgCl electrode (filled KCl 3 mol.L⁻¹) from Metrohm® (reference electrode); a platinum spiral electrode, as an auxiliary electrode, and a carbon paste electrode chemically modified with Cu (II) trans 3-MeO complex (as working electrode). Two forms of cocaine were analyzed: cocaine hydrochloride (pH 3) and cocaine free base form (pH 8). The PM7 computational method predicted that the hydrochloride form is more stable than the free base form of cocaine, so with cyclic voltammetry, we found electrochemical signal only for cocaine in the form of hydrochloride, with an anodic peak at 1.10 V, with a linearity range between 2 and 20 μmol L⁻¹ had LD and LQ of 2.39 and 7.26x10-5 mol L⁻¹, respectively. The study also proved that cocaine is adsorbed on the surface of the working electrode, where through an irreversible process, where only anode peaks are observed, we have the oxidation of cocaine, which occurs in the hydrophilic region due to the loss of two electrons. The mechanism of this reaction was confirmed by the ab-inito quantum method.

Keywords: ab-initio computational method, analytical method, cocaine, Schiff base complex, voltammetry

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Authors: Radka Gorejova, Ivana Sisolakova, Jana Shepa, Frederika Chovancova, Renata Orinakova

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Diabetes mellitus (DM) is a serious metabolic disease characterized by chronic hyperglycemia. Often, the symptoms are not sufficiently observable at early stages, and so hyperglycemia causes pathological and functional changes before the diagnosis of the DM. Therefore, the development of an electrochemical sensor that will be fast, accurate, and instrumentally undemanding is currently needful. Screen-printed carbon electrodes (SPCEs) can be considered as the most suitable matrix material for insulin sensors because of the small size of the working electrode. It leads to the analyst's volume reduction to only 50 µl for each measurement. The surface of bare SPCE was modified by a combination of chitosan, multi-walled carbon nanotubes (MWCNTs), and zinc nanoparticles (ZnNPs) to obtain better electrocatalytic activity towards insulin oxidation. ZnNPs were electrochemically deposited on the chitosan-MWCNTs/SPCE surface using the pulse deposition method. Thereafter, insulin was determined on the prepared electrode using chronoamperometry and electrochemical impedance spectroscopy (EIS). The chronoamperometric measurement was performed by adding a constant amount of insulin in 0.1 M NaOH and PBS (2 μl) with the concentration of 2 μM, and the current response of the system was monitored after a gradual increase in concentration. Subsequently, the limit of detection (LOD) of the prepared electrode was determined via the Randles-Ševčík equation. The LOD was 0.47 µM. Prepared electrodes were studied also as the impedimetric sensors for insulin determination. Therefore, various insulin concentrations were determined via EIS. Based on the performed measurements, the ZnNPs/chitosan-MWCNTs/SPCE can be considered as a potential candidate for novel electrochemical sensor for insulin determination. Acknowledgments: This work has been supported by the projects Visegradfund project number 22020140, VEGA 1/0095/21 of the Slovak Scientific Grant Agency, and APVV-PP-COVID-20-0036 of the Slovak Research and Development Agency.

Keywords: zinc nanoparticles, insulin, chronoamperometry, electrochemical impedance spectroscopy

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Authors: Marcin Kruszewski, Barbara Sochanowicz, Sylwia Męczyńska-Wielgosz, Maria Wojewódzka, Lucyna Kapka-Skrzypczak

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Metallic NPs are widely used in a number of applications in industry, science and medicine. Among metallic NPs foreseen to be widely used in medicine are gold nanoparticles (AuNPs) due to their low toxicity, and silver NPs (AgNPs) due to their strong antimicrobial activity. In this study, we compared an effect of AgNPs and gold NPs (AuNPs) on the formation of DNA damage and global DNA methylation and in A2780 and 4T1 cell lines, widely used models of human ovarian carcinoma and murine mammary carcinoma, respectively. The cells were treated with AgNPs coated with citrate (AgNPs(cit) or PEG (AgNPs(PEG), or AuNPs. A global DNA methylation was investigated with ELISA, whereas the formation of DNA damage was investigated by a comet +/- FPG. AgNPs decreased global DNA methylation and increased the formation of DNA lesions in both cell lines. The effect was dependent on the type of NPs used, it's coating, and cell line used. In conclusion, the epigenetic and genotoxic effects of NPs strongly depends on NP nature and cellular context. Epigenetic changes observed upon the action of AgNPs may play a crucial role in NPs-induced changes in protein expression.

Keywords: DNA damage, gold nanoparticles, methylation, silver nanoparticles

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Authors: Illyas Md Isa, Sharifah Norain Mohd Sharif, Norhayati Hashima

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A mercury(II) sensor was developed by using multi-walled carbon nanotubes (MWCNTs) paste electrode modified with Zn/Al layered double hydroxide-3(4-methoxyphenyl)propionate nanocomposite (Zn/Al-HMPP). The optimum conditions by cyclic voltammetry were observed at electrode composition 2.5% (w/w) of Zn/Al-HMPP/MWCNTs, 0.4 M potassium chloride, pH 4.0, and scan rate of 100 mVs-1. The sensor exhibited wide linear range from 1x10-3 M to 1x10-7 M Hg2+ and 1x10-7 M to 1x10-9 M Hg2+, with a detection limit of 1x10-10 M Hg2+. The high sensitivity of the proposed electrode towards Hg(II) was confirmed by double potential-step chronocoulometry which indicated these values; diffusion coefficient 1.5445 x 10-9 cm2 s-1, surface charge 524.5 µC s-½ and surface coverage 4.41 x 10-2 mol cm-2. The presence of 25-fold concentration of most metal ions had no influence on the anodic peak current. With characteristics such as high sensitivity, selectivity and repeatability the electrode was then proposed as the appropriate alternative for the determination of mercury(II).

Keywords: cyclic voltammetry, mercury(II), modified carbon paste electrode, nanocomposite

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Authors: Illyas Md Isa, Sharifah Norain Mohd Sharif, Norhayati Hashim

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A mercury(II) sensor was developed by using multi-walled carbon nano tubes (MWCNTs) paste electrode modified with Zn/Al layered double hydroxide-3(4-methoxyphenyl) propionate nano composite (Zn/Al-HMPP). The optimum conditions by cyclic voltammetry were observed at electrode composition 2.5% (w/w) of Zn/Al-HMPP/MWCNTs, 0.4 M potassium chloride, pH 4.0, and scan rate of 100 mVs-1. The sensor exhibited wide linear range from 1x10-3 M to 1x10-7 M Hg2+ and 1x10-7 M to 1x10-9 M Hg2+, with a detection limit of 1 x 10-10 M Hg2+. The high sensitivity of the proposed electrode towards Hg(II) was confirmed by double potential-step chronocoulometry which indicated these values; diffusion coefficient 1.5445 x 10-9 cm2 s-1, surface charge 524.5 µC s-½ and surface coverage 4.41 x 10-2 mol cm-2. The presence of 25-fold concentration of most metal ions had no influence on the anodic peak current. With characteristics such as high sensitivity, selectivity and repeatability the electrode was then proposed as the appropriate alternative for the determination of mercury.

Keywords: Cyclic voltammetry, Mercury(II), Modified carbon paste electrode, Nanocomposite

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Authors: Lucian Mocan, Teodora Mocan, Matea Cristian, Cornel Iancu

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We present method of nanoparticle enhanced laser thermal ablation of Klebsiella pneumoniae infections, using gold nanoparticles combined with a specific growth factor and demonstrate its selective therapeutic efficacy. Ab (antibody solution) bound to GNPs (gold nanoparticles) was administered in vitro and determined the specific delivery of the nano-bioconjugate into the microorganism. The extent of necrosis was considerable following laser therapy, and at the same time, normal cells were not seriously affected. The selective photothermal ablation of the infected tissue was obtained after the selective accumulation of Ab bound to GNPs into bacteria following perfusion. These results may represent a major step in antibiotherapy treatment using nanolocalized thermal ablation by laser heating.

Keywords: gold nanoparticles, Klebsiella pneumoniae, nanoparticle functionalization, laser irradiation, antibody

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Authors: Yu. Mateyshina, A. Ulihin, N. Uvarov

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Supercapacitors are one of the most promising devices for energy storage applications as they can provide higher power density than batteries and higher energy density than conventional dielectric capacitors. Carbon materials with various microtextures are considered as main candidates for supercapacitors in terms of high surface area, interconnected pore structure, controlled pore size, high electrical conductivity and environmental friendliness. The specific capacitance (C) of the electrode material of the Electrochemical Double Layer Capacitors (EDLC) is known to depend on the specific surface area (Ss) and the pore structure. Activated carbons are most commonly used in supercapacitors because of their high surface area (Ss ≥ 1000 m2/g), good adhesion to electrolytes and low cost. In this work, electrochemical properties of new microporous and mesoporous carbon electrode materials were studied. The aim of the work was to investigate the relationship between the specific capacitance and specific surface area in a series of materials prepared from different organic precursors.. As supporting matrixes different carbon samples with Ss = 100-2000 m2/g were used. The materials were modified by treatment in acids (H2SO4, HNO3, acetic acid) in order to enable surface hydrophilicity. Then nanoparticles of transition metal oxides (for example NiO) were deposited on the carbon surfaces using methods of salts impregnation, mechanical treatment in ball mills and the precursors decomposition. The electrochemical characteristics of electrode hybrid materials were investigated in a symmetrical two-electrode cell using an impedance spectroscopy, voltammetry in both potentiodynamic and galvanostatic modes. It was shown that the value of C for the materials under study strongly depended on the preparation method of the electrode and the type of electrolyte (1 M H2SO4, 6 M KOH, 1 M LiClO4 in acetonitryl). Specific capacity may be increased by the introduction of nanoparticles from 50-100 F/g for initial carbon materials to 150-300 F/g for nanocomposites which may be used in supercapacitors. The work is supported by the по SC-14.604.21.0013.

Keywords: supercapacitors, carbon electrode, mesoporous carbon, electrochemistry

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Authors: A. Hamam, D. Oukil, A. Dib, L. Makhloufi

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The aim of this work is to synthesize modified Polypyrrole films (PPy) containing nanoparticles of copper oxides onto a non conducting cellulosic substrate. Firstly, the chemical polymerization of polypyrrole onto cellulosic substrate is carried out using FeCl3 as an oxidant and Pyrrole as monomer. Different parameters were optimized (monomer concentration, duration of the experiment, nature of supporting electrolyte, temperature, etc.) in order to obtain films with different thickness and different morphologies. Thickness and topography of different PPy deposits were estimated by a profilometer apparatus. The electrochemical reactivity of the obtained electrodes were tested by cyclic voltammetry technique (CV) and electrochemical impedance spectroscopy (EIS). Secondly, the modification of the PPy film surface by incorporation of copper oxide nanonoparticles is conducted by applying a galvanostatic procedure from CuCl2 solution. Surface characterization has been carried out using scanning microscope (SEM) coupled with energy dispersive X-ray analysis (EDX), Fourier-transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The analysis showed the presence of the copper oxide nanoparticles (CuO) in the polymer films with dimensions less than 50 nm.

Keywords: polypyrrole, modified electrode, cellulosic substrate, copper oxide

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Authors: Bingjie Wang, Su-Yeon Kwon, Ik-Joong Kang

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The goal of this experiment is to develop a sensor that can quickly check the concentration by using the nanoparticles made by chitosan and gold. Using chitosan nanoparticles crosslinking with sodium tripolyphosphate(TPP) is the first step to form the chitosan nanoparticles, which would be covered with the gold sequentially. The size of the fabricated product was around 100nm. Based on the method that the sulfur end of the MPA linked to gold can form the very strong S–Au bond, and the carboxyl group, the other end of the MPA, can easily absorb the GABA. As for the GABA, what is the primary inhibitory neurotransmitter in the mammalian central nervous system in the human body. It plays such significant role in reducing neuronal excitability pass through the nervous system. A Surface-enhanced Raman Scattering (SERS) as the principle for enhancing Raman scattering by molecules adsorbed on rough metal surfaces or by nanostructures is used to detect the concentration change of γ-Aminobutyric Acid (GABA). When the system is formed, it generated SERS, which made a clear difference in the intensity of Raman scattering within the range of GABA concentration. So it is obtained from the experiment that the calibration curve according to the GABA concentration relevant with the SERS scattering. In this study, DLS, SEM, FT-IR, UV, SERS were used to analyze the products to obtain the conclusion.

Keywords: mercaptopropionic acid, chitosan-gold nanoshell, γ-aminobutyric acid, surface-enhanced raman scattering

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Authors: Mohamad Syahrizal Ahmad, Illyas M. Isa

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In this paper, a multiwall carbon nanotubes (MWCNT) paste electrode modified by a Zn layered hydroxide-ferulate (ZLH-F) was used for detection of hydroquinone (HQ). The morphology and characteristic of the ZLH-F/MWCNT were investigated by scanning electron microscope (SEM), transmission electron microscope (TEM) and square wave voltammetry (SWV). Under optimal conditions, the SWV response showed linear plot for HQ concentration in the range of 1.0×10⁻⁵ M – 1.0×10⁻³ M. The detection limit was found to be 5.7×10⁻⁶ M and correlation coefficient of 0.9957. The glucose, fructose, sucrose, bisphenol A, acetaminophen, lysine, NO₃⁻, Cl⁻ and SO₄²⁻ did not interfere the HQ response. This modified electrode can be used to determine HQ content in wastewater and cosmetic cream with range of recovery 97.8% - 103.0%.

Keywords: 1, 4-dihydroxybenzene, hydroquinone, multiwall carbon nanotubes, square wave voltammetry

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Authors: Lucyna Kapka-Skrzypczak, Barbara Sochanowicz, Magdalena Matysiak-Kucharek, Magdalena Czajka, Krzysztof Sawicki, Marcin Kruszewski

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Due to the strong antimicrobial activity silver nanoparticles (AgNPs) are widely used in various medical and general applications, among others, in cosmetics, odour resistant textiles, etc. The aim of this study was to compare effect of AgNPs and gold NPs (AuNPs) on histones posttranslational modifications. Histone molecule posttranscriptional modifications are responsible for chromatin compaction and repackaging. In this study, BALB/c mice were inoculated with murine mammary carcinoma 4T1 cells and treated with AgNPs coated with citrate (AgNPs(cit) or PEG (AgNPs(PEG), or AuNPs. Thereafter the histone H3 acetylation on Lys9 and H3 methylation on Lys4, Lys9, Lys29 was investigated. All NPs tested decreased H3 methylation, while no effect was observed for H3 acetylation. Modification of histone H3 methylation dependent on type of NPs used its coating, site of methylation and treatment used. Conclusion, epigenetic effects of nanomaterials depend on nanomaterial composition, its coating, and way of application. This work was supported by National Science Centre grant No. 2014/15/B/NZ7/01036 (MK, LKS, MMK, MC, KS), statutory funding for INTC (BS).

Keywords: gold nanoparticles, histone, methylation, silver nanoparticles

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Authors: Simona Dostalova, Pavel Kopel, Marketa Vaculovicova, Vojtech Adam, Rene Kizek

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Protein apoferritin seems to be a very promising structure for use as a nanocarrier. It is prepared from intracellular ferritin protein naturally found in most organisms. The role of ferritin proteins is to store and transport ferrous ions. Apoferritin is a hollow protein cage without ferrous ions that can be prepared from ferritin by reduction with thioglycolic acid or dithionite. The structure of apoferritin is composed of 24 protein subunits, creating a sphere with 12 nm in diameter. The inner cavity has a diameter of 8 nm. The drug encapsulation process is based on the response of apoferritin structure to the pH changes of surrounding solution. In low pH, apoferritin is disassembled into individual subunits and its structure is “opened”. It can then be mixed with any desired cytotoxic drug and after adjustment of pH back to neutral the subunits are reconnected again and the drug is encapsulated within the apoferritin particles. Excess drug molecules can be removed by dialysis. The receptors for apoferritin, SCARA5 and TfR1 can be found in the membrane of both healthy and cancer cells. To enhance the specific targeting of apoferritin nanocarrier, it is possible to modify its surface with targeting moieties, such as antibodies. To ensure sterically correct complex, we used a a peptide linker based on a protein G with N-terminus affinity towards Fc region of antibodies. To connect the peptide to the surface of apoferritin, the C-terminus of peptide was made of cysteine with affinity to gold. The surface of apoferritin with encapsulated doxorubicin (ApoDox) was coated either with gold nanoparticles (ApoDox-Nano) or gold (III) chloride hydrate reduced with sodium borohydride (ApoDox-HAu). The applied amount of gold in form of gold (III) chloride hydrate was 10 times higher than in the case of gold nanoparticles. However, after removal of the excess unbound ions by electrophoretic separation, the concentration of gold on the surface of apoferritin was only 6 times higher for ApoDox-HAu in comparison with ApoDox-Nano. Moreover, the reduction with sodium borohydride caused a loss of doxorubicin fluorescent properties (excitation maximum at 480 nm with emission maximum at 600 nm) and thus its biological activity. Fluorescent properties of ApoDox-Nano were similar to the unmodified ApoDox, therefore it was more suited for the intended use. To evaluate the specificity of apoferritin modified with antibodies, we used ELISA-like method with the surface of microtitration plate wells coated by the antigen (goat anti-human IgG antibodies). To these wells, we applied ApoDox without targeting antibodies and ApoDox-Nano modified with targeting antibodies (human IgG antibodies). The amount of unmodified ApoDox on antigen after incubation and subsequent rinsing with water was 5 times lower than in the case of ApoDox-Nano modified with targeting antibodies. The modification of non-gold ApoDox with antibodies caused no change in its targeting properties. It can therefore be concluded that the demonstrated procedure allows us to create nanocarrier with enhanced targeting properties, suitable for nanomedicine.

Keywords: apoferritin, doxorubicin, nanocarrier, targeting antibodies

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Authors: Illyas Isa, Mohamad Idris Saidin, Mustaffa Ahmad, Norhayati Hashim

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A highly selective and sensitive electrode for determination of trace amounts of Cu (II) using square wave anodic stripping voltammetry (SWASV) was proposed. The electrode was made of the paste of multiwall carbon nanotubes (MWCNT) and 2,6–diacetylpyridine-di-(1R)–(-)–fenchone diazine tetracarbonylmolybdenum(0) at 100:5 (w/w). Under optimal conditions the electrode showed a linear relationship with concentration in the range of 1.0 × 10–10 to 1.0 × 10– 6 M Cu (II) and limit of detection 8.0 × 10–11 M Cu (II). The relative standard deviation (n = 5) of response to 1.0 × 10–6 M Cu(II) was 0.036. The interferences of cations such as Ni(II), Mg(II), Cd(II), Co(II), Hg(II), and Zn(II) (in 10 and 100-folds concentration) are negligible except from Pb (II). Electrochemical impedance spectroscopy (EIS) showed that the charge transfer at the electrode-solution interface was favorable. Result of analysis of Cu(II) in several water samples agreed well with those obtained by inductively coupled plasma-optical emission spectrometry (ICP-OES). The proposed electrode was then recommended as an alternative to spectroscopic technique in analyzing Cu (II).

Keywords: chemically modified electrode, Cu(II), Square wave anodic stripping voltammetry, tetracarbonylmolybdenum(0)

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Authors: Chundong Li, V. V. Neshchimenko, M. M. Mikhailov

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The effect of the modification of ZnO powders by ZrO2, Al2O3, TiO2, SiO2, CeO2 and Y2O3 nanoparticles with a concentration of 1-30 wt % is investigated by diffuse reflectance spectra within the wavelength range 200 to 2500 nm before and after 100 keV proton and electron irradiation. It has been established that the introduction of nanoparticles ZrO2, Al2O3 enhances the optical stability of the pigments under proton irradiation, but reduces it under electron irradiation. Modifying with TiO2, SiO2, CeO2, Y2O3 nanopowders leads to decrease radiation stability in both types of irradiation. Samples modified by 5 wt. % of ZrO2 nanoparticles have the highest stability of optical properties after proton exposure. The degradation of optical properties under electron irradiation is not high for this concentration of nanoparticles. A decrease in the absorption of pigments modified with nanoparticles proton exposure is determined by a decrease in the intensity of bands located in the UV and visible regions. After electron exposure the absorption bands have in the whole spectrum range.

Keywords: irradiation, nanopowders, radiation stability, zinc oxide

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Authors: Šárka Hradilová, Aleš Panáček, Radek Zbořil

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Nanotechnologies are considered the most promising fields with high added value, brings new possibilities in various sectors from industry to medicine. With the growing of interest in nanomaterials and their applications, increasing nanoparticle production leads to increased exposure of people and environment with ‘human made’ nanoparticles. Nanoparticles (NPs) are clusters of atoms in the size range of 1–100 nm. Metal nanoparticles represent one of the most important and frequently used types of NPs due to their unique physical, chemical and biological properties, which significantly differ from those of bulk material. Biological properties including toxicity of metal nanoparticles are generally determined by their size, size distribution, shape, surface area, surface charge, surface chemistry, stability in the environment and ability to release metal ions. Therefore, the biological behavior of NPs and their possible adverse effect cannot be derived from the bulk form of material because nanoparticles show unique properties and interactions with biological systems just due to their nanodimensions. Silver and gold NPs are intensively studied and used. Both can be used for instance in surface enhanced Raman spectroscopy, a considerable number of applications of silver NPs is associated with antibacterial effects, while gold NPs are associated with cancer treatment and bio imaging. Antibacterial effects of silver ions are known for centuries. Silver ions and silver-based compounds are highly toxic to microorganisms. Toxic properties of silver NPs are intensively studied, but the mechanism of cytoxicity is not fully understood. While silver NPs are considered toxic, gold NPs are referred to as toxic but also innocuous for eukaryotic cells. Therefore, gold NPs are used in various biological applications without a risk of cell damaging, even when we want to suppress the growth of cancer cells. Thus, gold NPs are toxic or harmless. Because most studies comparing particles of various sizes prepared in various ways, and testing is performed on different cell lines, it is very difficult to generalize. The novelty and significance of our research is focused to the complex biological effects of silver and gold NPs prepared by the same method, have the same parameters and the same stabilizer. That is why we can compare the biological effects of pure nanometals themselves based on their chemical nature without the influence of other variable. Aim of our study therefore is to compare the cytotoxic effect of two types of noble metal NPs focusing on the mechanisms that contribute to cytotoxicity. The study was conducted on murine fibroblasts by selected common used tests. Each of these tests monitors the selected area related to toxicity and together provides a comprehensive view on the issue of interactions of nanoparticles and living cells.

Keywords: cytotoxicity, gold nanoparticles, mechanism of cytotoxicity, silver nanoparticles

Procedia PDF Downloads 238

Authors: Wen-Hsi Lee, C.G. Kao

Abstract:

In this study, Cu paste was prepared and printed with narrow line screen printing process on polycrystalline Si solar cell which has already finished the back Al printing and deposition of double anti-reflection coatings (DARCs). Then, two-step firing process was applied to sinter the front electrode and obtain the ohmic contact between front electrode and solar cell. The first step was in air atmosphere. In this process, PbO-based glass frit etched the DARCs and Ag recrystallized at the surface of Si, constructing the preliminary contact. The second step was in reducing atmosphere. In this process, CuO reduced to Cu and sintered. Besides, Ag nanoparticles recrystallized in the glass layer at interface due to the interactions between H2, Ag and PbO-based glass frit and the volatility of Pb, constructing the ohmic contact between electrode and solar cell. By experiment and analysis, reaction mechanism in each stage was surmised, and it was also proven that ohmic contact and good sheet resistance for front electrode could both be obtained by applying newly-invented paste and process.

Keywords: front electrode, solar cell, ohmic contact, screen printing, paste

Procedia PDF Downloads 323

Authors: M. Ghasemi-Varnamkhasti, S. H. Yoosefian, A. Mohammad-Razdari

Abstract:

This study investigated the effects of Ag nanoparticle polyethylene film and active modified atmosphere on the postharvest quality of tomatoes stored at 6 ºC. The atmosphere composition used in the packaging was 7% O₂ + 7% CO₂ + 86% N₂, and synthetic air (control). The variables measured were weight loss, firmness, color and respiration rate over 21 days. The results showed that the combination of Ag nanoparticle polyethylene film and modified atmosphere could extend the shelf life of tomatoes to 21 days and could influence the postharvest quality of tomatoes. Also, existence of Ag nanoparticles caused preventing from increasing weight loss, a*, b*, Chroma, Hue angle and reducing firmness and L*. As well as, tomatoes at Ag nanoparticle polyethylene films had lower respiration rate than Polyethylene and paper bags to 13.27% and 23.50%, respectively. The combination of Ag nanoparticle polyethylene film and active modified atmosphere was effective with regard to delaying maturity during the storage period, and preserving the quality of tomatoes.

Keywords: ag nanoparticles, modified atmosphere, polyethylene film, tomato

Procedia PDF Downloads 267

Authors: Z. Khalifa, K. M. Hassan, M. Abdel Azzem

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Potential strategies for deriving useful forms of renewable high density energy from abundant energy stored in carbohydrates is direct conversion of glucose (GLU) to electrical power. A three novel versatile modified electrodes, synthesized by electrochemical polymerization of organic monomers on glassy carbon electrodes (GC), have been developed for biofuel cells results in stable and long-term power production. Electrocatalytic oxidation of glucose in alkaline solution on conducting polymers electrodes modified by incorporation of Ni nanoparticles (NiNPs) onto poly(1,5-aminonaphthalene) (1,5-PDAN), poly(1,8-diaminonaphthalene) (1,8-PDAN) and poly(1-amino-2-methyl-9,10-anthraquinone) (PAMAQ) was investigated. The electrocatalytic oxidation of glucose at NiNPs-modified 1,5-PDAN/GC, 1,8-PDAN/GC and PAMAQ/GC electrodes has been studied using voltammetry technique. The PDAN electrodes show a slight activity in the potential of interest. The prepared NiNPs/PAMAQ/GC catalyst showed a very interesting catalytic activity that was nicely comparable to the NiNPs/1,5-PDAN/GC, NiNPs/1,8-PDAN/GC modified electrodes. In advance, both shows a significant more catalytic activity compared to the reported data for electrodes for glucose electrocatalytic oxidation.

Keywords: biofuel cells, glucose oxidation, electrocatalysis, nanoparticles and modified electrodes

Procedia PDF Downloads 233

Authors: Shahnaz Ashrafpour, Tahereh Tohidi Moghadam, Bijan Ranjbar

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Identifying the nature of protein-nanoparticle interactions and favored binding sites is an important issue in functional characterization of biomolecules and their physiological responses. Herein, interaction of silver nanoparticles with lysozyme as a model protein has been monitored via fluorescence spectroscopy. Formation of complex between the biomolecule and silver nanoparticles (AgNPs) induced a steady state reduction in the fluorescence intensity of protein at different concentrations of nanoparticles. Tryptophan fluorescence quenching spectra suggested that silver nanoparticles act as a foreign quencher, approaching the protein via this residue. Analysis of the Stern-Volmer plot showed quenching constant of 3.73 µM−1. Moreover, a single binding site in lysozyme is suggested to play role during interaction with AgNPs, having low affinity of binding compared to gold nanoparticles. Unfolding studies of lysozyme showed that complex of lysozyme-AgNPs has not undergone structural perturbations compared to the bare protein. Results of this effort will pave the way for utilization of sensitive spectroscopic techniques for rational design of nanobiomaterials in biomedical applications.

Keywords: nanocarrier, nanoparticles, surface plasmon resonance, quenching fluorescence

Procedia PDF Downloads 315

Authors: Elaf Ahmed, Shahid Rasul, Ohoud Alharbi, Peng Wang

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Ultra-Small Nanoparticles of metals (USNPs) have attracted the attention from the perspective of both basic and developmental science in a wide range of fields. These NPs exhibit electrical, optical, magnetic, and catalytic phenomena. In addition, they are considered effective catalysts because of their enormously large surface area. Many chemical methods of synthesising USNPs are reported. However, the drawback of these methods is the use of different capping agents and ligands in the process of the production such as Polyvinylpyrrolidone, Thiol and Ethylene Glycol. In this research ultra-small nanoparticles of gold, palladium and platinum metal have been successfully produced using electrochemically active biofilm (EAB) after optimising the pH of the media. The production of ultra-small nanoparticles has been conducted in a reactor using a simple two steps method. Initially biofilm was grown on the surface of a carbon paper for 7 days using Shewanella Loihica bacteria. Then, biofilm was employed to synthesise platinum, palladium and gold nanoparticles in water using sodium lactate as electron donor without using any toxic chemicals at mild operating conditions. Electrochemically active biofilm oxidise the electron donor and produces electrons in the solution. Since these electrons are a strong reducing agent, they can reduce metal precursors quite effectively and quickly. The As-synthesized ultra-small nanoparticles have a size range between (2-7nm) and showed excellent catalytic activity on the degradation of methyl orange. The growth of metal USNPs is strongly related to the condition of the EAB. Where using low pH for the synthesis was not successful due to the fact that it might affect and destroy the bacterial cells. However, increasing the pH to 7 and 9, led to the successful formation of USNPs. By changing the pH value, we noticed a change in the size range of the produced NPs. The EAB seems to act as a Nano factory for the synthesis of metal nanoparticles by offering a green, sustainable and toxic free synthetic route without the use of any capping agents or ligands and depending only on their respiration pathway.

Keywords: electrochemically active biofilm, electron donor, shewanella loihica, ultra-small nanoparticles

Procedia PDF Downloads 184

Authors: Lei Hou, Xinli Du, Nikolaos Boulgouris

Abstract:

A cochlear implant, referred to as a CI, is a small electronic device that can provide direct electrical stimulation to the auditory nerve. During cochlear implant surgery, atraumatic electrode array insertion is considered to be a crucial step. However, during implantation, the mechanical behaviour of an electrode array inside the cochlea is not known. The behaviour of an electrode array inside of the cochlea is hardly identified by regular methods. In this study, a CI electrode array capacitive sensor system is proposed. It is able to automatically determine the array state as a result of the capacitance variations. Instead of applying sensors to the electrode array, the capacitance information from the electrodes will be gathered and analysed. Results reveal that this sensing method is capable of recognising different states when fed into a pre-shaped model.

Keywords: cochlear implant, electrode, hearing preservation, insertion force, capacitive sensing

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Authors: V. Balamuralidhara

Abstract:

The aim of the present work was to develop Paclitaxel loaded polyacrylamide grafted guar gum nanoparticles as pH responsive nanoparticle systems for targeting colon. The pH sensitive nanoparticles were prepared by modified ionotropic gelation technique. The prepared nanoparticles showed mean diameters in the range of 264±0.676 nm to 726±0.671nm, and a negative net charge 10.8 mV to 35.4mV. Fourier Transformed Infrared Spectroscopy (FT-IR) and Differential Scanning Calorimetry (DSC) studies suggested that there was no chemical interaction between drug and polymers. The encapsulation efficiency of the drug was found to be 40.92% to 48.14%. The suitability of the polyacrylamide grafted guar gum ERN’s for the release of Paclitaxel was studied by in vitro release at pH 1.2 and 7.4. It was observed that, there was no significant amount of drug release at gastric pH and 97.63% of drug release at pH 7.4 was obtained for optimized formulation F3 at the end of 12 hrs. In vivo drug targeting performance for the prepared optimized formulation (F3) and pure drug Paclitaxel was evaluated by HPLC. It was observed that the polyacrylamide grafted guar gum can be used to prepare nanoparticles for targeting the drug to the colon. The release performance was greatly affected by the materials used in ERN’s preparation, which allows maximum release at colon’s pH. It may be concluded that polyacrylamide grafted guar gum nanoparticles loaded with paclitaxel have desirable release responsive to specific pH. Hence it is a unique approach for colonic delivery of drug having appropriate site specificity and feasibility and controlled release of drug.

Keywords: colon targeting, polyacrylamide grafted guar gum nanoparticles, paclitaxel, nanoparticles

Procedia PDF Downloads 342