A new electrochemical sensor designed by modifying the commercial boron-doped diamond (BDD) electrode with graphene oxide (GO) reduced electrochemically and further electrodecorated with silver (Ag), ...named the Ag/GO/BDD electrode, was selected among a series of the BDD, GOelectroreduced onto BDD (GO/BDD) and silver electrodeposited onto BDD (Ag/BDD) electrodes for the detection of tetracycline (TC) in aqueous solution. The best results regarding the sensitivity of 46.6 µA·µM
·cm
and the lowest limit of detection of 5 nM was achieved using square-wave voltammetry (SWV) operated at the step potential of 5 mV, modulation amplitude of 200 mV and the frequency of 10 Hz in alkaline medium. The application of the alkaline supporting electrolyte-based procedure is limited for water monitoring due to the presence of chloride that interferes with TC detection; however, it can be applied for quantitative determination of pharmaceutical formulations. 0.1 M Na
SO
supporting electrolyte eliminated chloride interference and can be used for the application of Ag/GO/BDD in practical detection of TC in water.
In this work, a ferrocene-containing gallic acid-derivative modified carbon-nanotube paste electrode (Gal-Fc-CNT), obtained through simple mechanical mixing, was studied for the fast simultaneous ...voltammetric determination of doxorubicin (DOX), capecitabine (CPB), and cyclophosphamide (CPP) as cytostatic indices based on their cumulative signals and the selective determination of DOX. The individual and simultaneous electrochemical behavior of DOX, CPB, and CPP, studied through cyclic voltammetry (CV) on the Gal-Fc-CNT paste electrode at various pHs and potential ranges, allowed for the development of a simple simultaneous determination method as a cytostatic index at a pH of 12 using square-wave voltammetry, which allowed for a better performance than reported electrodes for each individual cytostatic. A faster and selective detection of DOX, with a limit of detection of 75 ng·L−1, was achieved using square-wave voltammetry at a pH of 3. The good results obtained for the real tap water assessment indicated the applicability of the Gal-Fc-CNT paste electrode for practical applications (water samples).
A novel electrochemical glucose sensor was developed, based on a multiwall carbon nanotubes (MWCNTs)-copper-1,3,5-benzenetricarboxylic acid (CuBTC)-epoxy composite electrode, named MWCNT-CuBTC. The ...electrode nanocomposite was prepared by a two-roll mill procedure and characterized morphostructurally by scanning electron microscopy (SEM). The CuBTC formed defined crystals with a wide size distribution, which were well dispersed and embedded in the MWCNTs. Its electrical conductivity was determined by four-point probe contact (DC) conductivity measurements. The electroactive surface area, determined using cyclic voltammetry (CV), was found to be 6.9 times higher than the geometrical one. The results of the electrochemical measurements using CV, linear sweep voltammetry (LSV), differential pulse voltammetry (DPV), chronoamperometry (CA) and multiple pulse amperometry (MPA) showed that the MWCNT-CuBTC composite electrode displayed high electrocatalytic activity toward the oxidation of glucose and, as a consequence, very high sensitivity. The best sensitivity of 14,949 µAmM−1cm−1 was reached using MPA at the potential value of 0.6 V/SCE, which was much higher in comparison with other copper-based electrodes reported in the literature. The good analytical performance, low cost and simple preparation method make this novel electrode material promising for the development of an effective glucose sensor.
Nitrogen-doped titanium oxide thin films covered by gold metal nanoparticles were grown on (001) SiO
2
quartz substrates by pulsed laser deposition. A KrF* excimer laser source (
λ
= 248 nm,
τ
FWHM
... ≤ 25 ns,
ν
= 10 Hz) was used for the irradiation of TiO
2
and gold metal targets. The experiments were performed in controlled reactive oxygen or nitrogen atmosphere. The layers were grown for photocatalytic applications. Evaluation of photocatalytic activity was performed by photodegradation of methyl orange under near-UV light irradiation. Our results show that nitrogen doping and addition of gold nanoparticles have complementary effects, photoactivity being significantly improved as compared to that of pure titanium oxide.
In this study, ZnO has been used as inorganic shell material (in situ synthetized) for the encapsulation of KNO
3
, an inorganic molten salt commonly used in concentrated solar plants applications. ...The thermal stability of microparticles encapsulated by using a solvothermal process has been optimized by adjusting the parameters affecting the properties of the microparticles, such as the core:shell ratio and the temperature during the microencapsulation process. The energy stored and released after each thermal cycle was evaluated by differential scanning calorimetry. Chemical composition of microparticles was evaluated by infrared spectroscopy and inductively coupled plasma spectroscopy, as well as morphology was characterized by scanning electron microscopy. Results have shown the solvothermal synthesis as a feasible process for the microencapsulation of molten salts by obtaining KNO
3
particles covered by ZnO microcrystals. These particles have thermal energy storage and release capacities and temperatures similar to those of raw KNO
3
, being the temperature used during the solvothermal process the parameter determining the thermal stability of the microparticles, as demonstrated by carrying out durability tests through consecutive heating–cooling thermal cycles (250–400 °C).
Five samples of human midterm fetal uterus and fallopian tube (four donor bodies) were used to assess whether or not processes of angiogenesis are guided by endothelial tip cells (ETCs), and if ...cytokine-receptors, such as CD117/c-kit and PDGFR-α, are expressed in the microenvironment of the endothelial tubes. CD34 labeled microvessels in the uterine wall (myometrium and endometrium) and in the wall of the uterine (fallopian) tube, and accurately identified ETCs in both organs. We conclude that sprouting angiogenesis in the developing human female tract is guided by ETCs. Moreover, CD117/c-kit antibodies labeled mural networks of pericytes, α-SMA-positive and desmin-negative, related to the endometrial (but not myometrial) microvessels, and similar labeling was identified in the wall of the uterine tube. PDGFR-α positive labeling, stromal and pericytary, was also found. Thus, sprouting angiogenesis in human fetal genital organs appears to be guided by tip cells and is influenced by tyrosine kinase receptor signaling.
Ribonuclease A (RNase A) enzyme was immobilized on solid holders by matrix-assisted pulsed laser evaporation (MAPLE) technique. The experiments were performed inside a stainless steel irradiation ...chamber. A UV KrF* (λ = 248 nm, τ
FWHM
≅ 25 ns, ν = 10 Hz) excimer laser source was used for irradiations. Surface morphology, molecular structure, and enzymatic activity of laser transferred RNase A samples were investigated as a function of RNase A concentration in the frozen composite MAPLE targets. Surface morphology and thickness of the immobilized enzyme were investigated by atomic force microscopy, scanning electron microscopy, and surface profilometry. The molecular structure of the laser transferred RNase A was determined by Fourier transform infrared spectroscopy. The enzymatic activity of RNase A after immobilization was tested through ribonucleic acid removal from deoxyribonucleic acid (DNA) extract solutions isolated from plant and animal tissues. A molecular method based on polymerase chain reaction was used to investigate the functional properties of DNA extracts treated with laser immobilized RNase A.
Owing to its extraordinary range of properties, yttria-doped zirconia holds a unique place among the ceramic oxide systems. To improve the properties for some specific custom design applications, ...co-doping with other rare earth oxides such as ceria is needed. The aim of this paper is to identify the correlations between the phase composition evolution with increasing thermal treatment temperature in order to establish the thermal stability in connection with the ceria content and how does it influence the yttria-stabilised zirconia microstructure. The ZrO2–3Y2O3–nCeO2 (n = 3, 6 and 9 wt.%) samples were obtained by a hydrothermal process and submitted to a thermal treatment up to 1600 °C. Intensive characterization was performed via X-ray powder diffraction and EDX analysis. It was found that up to 400 °C, a monophasic structure was formed. At higher temperatures tetragonal zirconia is formed as a major phase with the presence of secondary monoclinic and cubic phases, depending on the Ce content and thermal treatment temperature. Sintered compacts with densities up to 99.5% from the theoretical density were obtained starting from the 6%CeO2–3%Y2O3–ZrO2-nanostructured powders using a special field-assisted (FAST) sintering process. With increasing CeO2 content to 9% only, tetragonal zirconia with 6–9 nm crystallite sizes is formed during the FAST sintering process.
There have been few studies on human embryos describing a specific pattern of hindgut colonization by hematopoietic stem cells (HSCs) and interstitial Cajal cells (ICCs). We aimed to study CD34, CD45 ...and CD117/c-kit expression in late stage human embryos, to attain observational data that could be related to studies on the aorta-gonad-mesonephros (AGM)-derived HSCs, and data on hindgut ICCs. Antibodies were also applied to identify alpha-smooth muscle actin and neurofilaments. Six human embryos of 48–56 days were used. In the 48 day embryo, the hindgut was sporadically populated by c-kit+ ICCs, but, in all other embryos, a layer of myenteric ICCs had been established. Intraneural c-kit+ cells were found in pelvic nerves and vagal trunks, suggesting that the theory of Ramon y Cajal assuming that ICCs may be primitive neurons may not be so invalid. Also in the 48 day embryo, c-kit+/CD45+ perivascular cells were found along the pelvic neurovascular axes, suggesting that not only liver, but also other organs could be seeded with HSCs from the AGM region. CD45+ cells with dendritic morphologies were found in all hindgut layers, including the epithelium. This last evidence is suggestive of an AGM contribution to the tissue resident macrophages and could be related to processes of sprouting angiogenesis which, in turn, have been found to be guided by filopodia of endothelial tip cells. Further studies on human embryonic and fetal material should be performed to attempt to clarify whether the hindgut colonization with HSCs is a transitory or definitive process.
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