The study presents a novel electrochemical biosensor for the determination of relative antioxidant capacity using a superoxide dismutase (SOD)-based biosensor. The biosensor contains ZnO nanostructures electrodeposited onto gold-coated electrospun polycaprolactone (PCL/Au) fibers. ZnO nanostructures with different morphologies were obtained by varying electrodeposition parameters and the resulting PCL/Au/ZnO platforms were morphologically and electrochemically characterized. SOD was immobilized onto PCL/Au/ZnO through three different strategies: covalent attachment via carbodiimide chemistry, entrapment within chitosan, and physical adsorption. The performance of PCL/Au/ZnO/SOD biosensors was evaluated by cyclic voltammetry and fixed-potential amperometry to assess the influence of ZnO morphology and immobilization strategy on biosensor's analytical performance. The optimized ZnO nanostructure significantly enhanced electron transfer and enzyme immobilization, resulting in improved sensitivity, reproducibility and analytical performance compared with the other electrodeposition conditions and was successfully applied to the determination of antioxidant capacity in complex beverage matrices, including red wine, green tea, and orange juice. Unlike conventional antioxidant assays based on synthetic radicals, the proposed biosensor selectively evaluates superoxide scavenging activity, providing biologically relevant information on antioxidant capacity.

This study investigates the development of electrochemical genosensors using gold-coated electrospun polymeric fibers electrodes, Au/PMMA/PET and immobilized phosphorothioated oligonucleotides. Scanning electron microscopy (SEM) with energy-dispersive X-rays spectroscopy (EDS) revealed a uniform distribution of oligonucleotides on the fibers, contrary to planar gold electrodes Au/Ti/SiO2/Si, where network-like films were observed. X-ray photoelectron spectroscopy (XPS) confirmed the successful immobilization of the phosphorothioated oligonucleotides via strong covalent gold-sulfur bonds, while surface plasmon resonance (SPR) indicated superior binding affinity, with significantly lower equilibrium dissociation constants, when compared to unmodified probes. The detection of BCR/ABL fusion gene of chronic myeloid leukemia using differential pulse voltammetry and methylene blue as electroactive indicator, showed that the Au/PMMA/PET electrodes achieved a sensitivity of 379 +/- 12 mu A cm(-)(2) pM(-)(1) and a limit of detection of similar to 5.00 +/- 0.01 fM, outperforming the Au/Ti/SiO2/Si planar electrodes. Reduced non-specific adsorption was observed on the Au/PMMA/PET electrodes and attributed to the inherent charges introduced during the electrospinning process, which created localized electrostatic fields that repelled weakly adsorbing molecules. These findings demonstrate the potential of Au/PMMA/PET electrodes as a robust platform for further development of high-performance clinical diagnostic devices.

Electrochemical replication of nanoporous membranes was employed for the fabrication of nickel nanowires. The fabrication process led to uniform arrays of quasi 1 dimensional nanoobjects with low diameters and high aspect ratios. Extensive characterization experiments were carried out for determining the morphological, structural and magnetic properties of the nanostructures. It was found that the working electrode potential employed during the electrochemical deposition fabrication experiments influences both the crystalline structure and the magnetic properties of the nanowires. Accordingly, an in-depth investigation of the correlations between the morpho-structural and the magnetic parameters was performed. It was shown that several structural factors, mainly crystalline texture and grain size and shape, quite sensitive to the deposition potential, influence also the specific magnetic configurations, which can be tuned from 3-dimensional Imry and Ma random anisotropy type to cooperative quasi-1-dimensional superspin type. Consequently, new possibilities in tailoring the magneto-functionalities of polycrystalline magnetic nanowires by adjusting fabrication parameters are revealed.

In this paper, graphene was obtained on a copper substrate using the CVD method, and then it was transferred to various substrates such as glass and SiO2/Si patterned with metallic interdigitated electrodes. The graphene thus obtained was characterized using Raman spectroscopy, scanning electron microscopy (SEM), current-voltage measurements, and electrochemical methods, in order to be used for sensing applications.

A novel electrochemical biosensor was developed to monitor fibroblast cells stress levels for the first time in situ under external stimuli based on the recognition of superoxide anion released upon cell damage. The biosensor comprised metallized polycaprolactone electrospun fibers covered with zinc oxide for improved cell adhesion and signal transduction, whilst stable bioconjugates of mercaptobenzoic acid-functionalized gold nanoparticles/superoxide dismutase were employed as recognition bioelements. Biosensors were first tested and optimized for in situ generated superoxide detection by fixed potential amperometry at +0.3 V, with minimal interferences from electroactive species in cell culture media. L929 fibroblast cells were then implanted on the optimized biosensor surface and the biosensor morphologically characterized by scanning electron microscopy (SEM) and fluorescence microscopy, which illustrated the network-type pattern of fibroblasts adjacent to the fiber scaffold. Fibroblast stress was induced by zymosan and monitored at the cells integrated biosensor using fixed potential amperometry (CA) with a sensitivity of 26 nA cm-2 μg mL-1 zymosan and electrochemical impedance spectroscopy (EIS), with similar sensitivity of the biosensor considering the Rs and Z' parameters of around 0.13 Ω cm2 μg-1 mL and high correlation factors R2 of 0.9994. The obtained results underline the applicability of the here developed biosensor for the electrochemical screening of the fibroblast cells stress. The concept in using low-cost biocompatible polymeric fibers as versatile scaffolds for both enzyme immobilization and cell adhesion, opens a new path in developing biosensors for the in-situ investigation of a variety of cellular events.

A sensor for the enzymatic activity and inhibition of the 20S proteasome was developed by immobilizing the synthetic peptide ABZ-VVSYAMG-(O2Oc)2-OH at Au electrodes. The detection principle is based on the electroactivity of ABZ, part of the ABZ-VVSY-OH moiety released from the peptide upon 20S proteasome chymotrypsin action. The peptide was immobilized on a para-amino thiophenol (PATP) self-assembled monolayer on Au electrode by cross-linking its amino group to the -(O2Oc)2-OH moiety of the peptide (Au/PATP/peptide). The immobilization of the peptide and its interaction with 20S proteasome was investigated by SEM, QCM, SPR, ATR-FTIR and electrochemistry. The activity of 20S proteasome was assessed electrochemically by cyclic voltammetry (CV) and electrochemical impedance spectra (EIS) after the immersion Au/PATP/peptide in 20S proteasome solution. CV study showed a decrease in both capacitive and faradaic currents corresponding to the ABZ-VVSY-OH removal, allowing the quantification of the 20S proteasome activity. The EIS study revealed that the resistance corresponding to charge transfer reactions at the peptide/solution interface correlated to the ABZ redox reaction, decreased linearly with increasing the incubation time in 20S proteasome solution. The perfected assay was applied for the investigation of the inhibitory effect of one synthetic, bortezomib, and two naturally occurring, epoxomicin, and lactacystin inhibitors.

The deposition of a ferromagnetic layer can affect the properties of high-temperature superconductors underneath. We investigated the influence of ferromagnetic CaRuO3 on the properties of YBa2Cu3O7-x (YBCO) superconducting thin films when the layers are either in direct contact or separated by a barrier layer of 5 nm SrTiO3. Detailed measurements of the magnetic moment of the superconductor and ferromagnet as a function of temperature and magnetic field have been performed using SQUID magnetometry. Magnetometry and relaxation measurements show that the modification of the superconducting properties of YBCO strongly depends on the interaction with the ferromagnetic layer on top. The barrier layer has a significant impact on both the supercon-ducting properties of the YBCO film and the ferromagnetic ordering of CaRuO3. The physical properties mentioned above were discussed in correlation with the materials' structure determined by XRD analysis.

The use of gold nanoparticles/superoxide dismutase (AuNP/SOD) bioconjugates is described as building blocks in SOD biosensor development for the quantification of superoxide in cell culture media. AuNP functionalization with 11-mercaptoundecanoic acid (MUA) and 4-mercaptobenzoic acid (MBA) (AuNPMUA and AuNPMBA) was used to improve SOD immobilization through EDC/NHS coupling using their –COOH terminus, leading to the formation of more stable bioconjugates. AuNP and AuNP/SOD bioconjugates were characterized by SEM to determine their size and morphology, UV–Vis for optical properties, FT-IR, and Raman spectroscopies for chemical functional group analysis and EDX for elemental analysis. Electrochemical methods were used to characterize the Au/AuNP-modified electrodes. For the optimization of the biosensor architecture, different AuNP/enzyme bioconjugates were prepared by varying the amount of both enzyme and AuNP, as well as their incubation time. Finally, the biosensors incorporating the bioconjugates were characterized by fixed potential amperometry and voltammetric analysis in order to establish the enzymatic mechanism and to elucidate the best biosensor architecture for monitoring superoxide in cell culture media. The best sensitivity value for superoxide detection corresponded to 41.2 nA µM cm−2, achieved by a biosensor based on AuNPMBA/SOD bioconjugates monitored through fixed potential amperometry at 0.3 V vs. Ag/AgCl, with a limit of detection of 1.0 µM, and overall very good operational stability, maintaining 91% of the initial sensitivity after 30 days. Finally, the optimized biosensor was employed for the quantification of successive additions of superoxide in cell culture media, with excellent recovery values.

The interaction of radiation with matter takes place through energy transfer and is accomplished especially by ionized atoms or molecules. The effect of radiation on biological systems involves multiple physical, chemical and biological steps. Direct effects result in a large number of reactive oxygen species (ROS) within and outside and inside of the cells as well, which are responsible for oxidative stress. Indirect effects are defined as alteration of normal biological processes and cellular components (DNA, protein, lipids, etc.) caused by the reactive oxygen species directly induced by radiation. In this work, a classical design of an electrochemical (EC) three-electrodes system was employed for analyzing the effects of proton beam radiation on melanoma B16 cell line. In order to investigate the effect of proton radiation on the B16 cells, the cells were grown on the EC surface and irradiated. After optimization of the experimental set-up and dosimetry, the radiobiological experiments were performed at doses ranging between 0 and 2 Gy and the effect of proton beam irradiation on the cells was evaluated by the means of cyclic voltammetry and measuring the open circuit potential between working and reference electrodes.

A novel and disposable biosensor based on superoxide dismutase (SOD) immobilized on gold metallized polycaprolactone electrospun polymeric fibers (PCl/Au) has been developed for the determination of superoxide (O-2(center dot-)) in cell culture media. SOD biosensors were constructed employing three immobilization methods: crosslinking with EDC/NHS at a cysteine self-assembled monolayer (PCl/Au/SODCYS), biopolymer encapsulation with chitosan (PCl/Au/SODCHI) and cross-linking with glutaraldehyde (PCl/Au/SODGA). Scanning electron microscopy was performed at the three different biosensors to evaluate their surface morphologies. Biosensors were employed for the electrochemical detection of superoxide by fixed potential amperometry at different applied potentials, with two distinct enzymatic mechanisms being proposed: i) the reduction of the enzymatically generated peroxide, at -0.3 V, for which the PCl/Au/SODCHI biosensor presented the highest value of sensitivity of 40.1 mu A mM(-1) cm(-2), and ii) the regeneration of the enzyme catalytic copper centre, at +0.3 V, for which the PCl/Au/SODCYS biosensor had the highest sensitivity value of 16.1 mu A mM(-1) cm(-2). The proposed recognition mechanisms were further confirmed by cyclic voltammetric measurements, which enabled also to determine the amount of immobilized electroactive SOD, with highest value corresponding to the PCl/Au/SODCYS biosensor. The biosensors with best analytical performance, PCl/Au/SODCYS and PCl/Au/SODCHI, were further investigated for stability and selectivity, with best results for the PCl/Au/SODCYS, chosen for superoxide monitoring in cell culture media. The study is promising for future application of PCl/Au/SODCYS for the on-line superoxide monitoring of superoxide in cell cultures, grown directly on the biosensor itself.

Almost all proposed configurations and practical achievements based on superconductor/ferromagnet (S/F) heterostrucutres focus on s-wave superconductors. However, several attempts targeted also high temperature superconductors, most of them using manganite ferromagnets LaXMnO3 (X: Ca or Sr) and Y1Ba2Cu3O7−x (YBCO). Here we propose a new ferromagnetic material that can be used with YBCO for the fabrication of S/F hybrid structures. We show that a ferromagnetic order can be induced in a thin layer (∼130 nm thickness) of CaRuO3 grown by pulsed laser deposition on epitaxial YBCO film. Detailed magnetic and structural investigations show that the observations of the weak ferromagnetism are consistent with the magnetic order induced by in-plane tensile strain of about 1.7% and the easy-magnetization axis forms an angle of ∼180º with the layer plane. The value of the Curie temperature T Curie estimated using the Curie–Weiss law was 340 K. An unusual temperature dependence of the magnetic moment around the superconducting transition was observed in both field-cooled and zero-field-cooled configurations which is attributed to the paramagnetic Meissner effect.

A dual strategy for the electrochemical detection for 20S proteasome (20S) is proposed, based on the oriented immobilization of a capture monoclonal antibody (Abβ) on a self-assembled monolayer of 4-mercaptophenylboronic acid (4-MPBA) on gold electrodes, which led to the Au/4-MPBA/Abβ immunosensor. The methodology comprises the correlation of 20S concentration with (i) its proteolytic activity toward the Z-LLE-AMC substrate, using the Au/4-MPBA/Abβ/20S, and (ii) the enzymatic activity of an alkaline phosphatase (AlkP) from the AlkP-labeled secondary antibody (Abcore-AlkP), which involves the conversion of aminophenylphosphate to the electroactive aminophenol using Au/4-MPBA/Abβ/20S/Abcore-AlkP. The step-by-step construction of the immunosensor and the interactions at its surface were evaluated by surface plasmon resonance and gravimetric analysis with quartz crystal microbalance, showing a high affinity between both antibodies and 20S. Morphological analysis by scanning electron microscopy demonstrated a pattern of parallel lines upon immobilization of Abβ on 4-MPBA and morphological changes to a well-organized granular structure upon binding of 20S. A voltametric and impedimetric characterization was performed after each step in the immunosensor construction. The two detection strategies were evaluated. It was shown that the immunosensor responds linearly with 20S concentration in the range between 5 and 100 µg mL−1, which corresponds to proteasome levels in serum in the case of diverse pathological situations, and LoD values of 1.4 and 0.2 µg mL−1 were calculated for the detection strategies. The immunosensor was applied to the detection of 20S in serum samples with recovery values ranging from 101 to 103%.

Nanoscale thermometers with high sensitivity are needed in domains which study quantum and classical effects at cryogenic temperatures. Here, we present a micrometer sized and nanometer thick chromium selenide cryogenic temperature sensor capable of measuring a large domain of cryogenic temperatures down to tenths of K. Hexagonal Cr-Se flakes were obtained by a simple physical vapor transport method and investigated using scanning electron microscopy, energy dispersive X-ray spectrometry and X-ray photoelectron spectroscopy measurements. The flakes were transferred onto Au contacts using a dry transfer method and resistivity measurements were performed in a temperature range from 7 K to 300 K. The collected data have been fitted by exponential functions. The excellent fit quality allowed for the further extrapolation of resistivity values down to tenths of K. It has been shown that the logarithmic sensitivity of the sensor computed over a large domain of cryogenic temperature is higher than the sensitivity of thermometers commonly used in industry and research. This study opens the way to produce Cr-Se sensors for classical and quantum cryogenic measurements.

Composites of magnetite (Fe3O4) nanoparticles dispersed in a polydimethylsiloxane (PDMS) matrix were prepared by a molding process. Two types of samples were obtained by free polymerization with randomly dispersed particles and by polymerization in an applied magnetic field. The magnetite nanoparticles were obtained from magnetic micrograins of acicular goethite (α-FeOOH) and spherical hematite (α-Fe2O3), as demonstrated by XRD measurements. The evaluation of morphological and compositional properties of the PDMS:Fe3O4 composites, performed by SEM and EDX, showed that the magnetic particles were uniformly distributed in the polymer matrix. Addition of magnetic dispersions promotes an increase of thermal conductivity compared with pristine PDMS, while further orienting the powders in a magnetic field during the polymerization process induces a decrease of the thermal conductivity compared with the un-oriented samples. The shape of the magnetic dispersions is an important factor, acicular dispersions providing a higher value for thermal conductivity compared with classic commercial powders with almost spherical shapes.

This work reports the use of electrospun conductive gold covered polycaprolactone fibers for the quantification of dissolved O2. The morphologies of the electrospun fibers obtained at a static and a dynamic drum collector were investigated by scanning electron microscopy. The reduction process of O2 at negative potentials is analyzed by cyclic voltammetry and electrochemical impedance spectroscopy (EIS) in sodium phosphate buffer (NaPB) pH 7.0 and in cellular media pH 7.4. The electrochemical sensing performance of Au/PCL towards O2 quantification in NaPB and cellular media is compared by using three electrochemical techniques: cyclic and linear sweep voltammetry and EIS. Measurements are done in a two electrode configuration, using a silver wire as reference, to show the applicability of the method for O2 quantification in cellular culture media.