Improvement of Magnetic Saturation in Fe3O4@Y2O3:Eu3+ Nanocomposites Through the Manipulation of Eu3+ Activators

Fe3O4@Y2O3:Eu3+ nanocomposites and Y2O3:Eu3+ nanophosphors were synthesized using the hydrothermal method. Nanocomposites were analyzed using X-ray diffraction (XRD), Rietveld refinements, Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, photoluminescence (PL), vibrating sample magnetometer (VSM), and high-resolution transmission electron microscopy (HRTEM). Nanocomposites exhibit superparamagnetic behavior that improves with Eu3+, resulting in increased magnetic saturation. In contrast to Y2O3:Eu3+ nanophosphors, the Fe3O4@Y2O3:Eu3+ nanocomposites display a distinctive characteristic whereby the photoluminescence intensity increases with a reduced concentration of Eu3+. The requirement of increasing the thickness of the Y2O3:Eu3+ outer layer to achieve improved light emission can be circumvented by solely manipulating the concentration of activators, without compromising the magnetic saturation of the nanocomposites. The luminescent and magnetic characteristics of Fe3O4@Y2O3:Eu3+ nanocomposites can be readily optimized using straightforward synthesis parameters, making them promising candidates for potential applications in theranostic medicine.

A Ferrofluid with Surface Modified Nanoparticles for Magnetic Hyperthermia and High ROS Production

A ferrofluid with 1,2-Benzenediol-coated iron oxide nanoparticles was synthesized and physicochemically analyzed. This colloidal system was prepared following the typical co-precipitation method, and superparamagnetic nanoparticles of 13.5 nm average diameter, 34 emu/g of magnetic saturation, and 285 K of blocking temperature were obtained. Additionally, the zeta potential showed a suitable colloidal stability for cancer therapy assays and the magneto-calorimetric trails determined a high power absorption density. In addition, the oxidative capability of the ferrofluid was corroborated by performing the Fenton reaction with methylene blue (MB) dissolved in water, where the ferrofluid was suitable for producing reactive oxygen species (ROS), and surprisingly a strong degradation of MB was also observed when it was combined with H2O2. The intracellular ROS production was qualitatively corroborated using the HT-29 human cell line, by detecting the fluorescent rise induced in 2,7-dichlorofluorescein diacetate. In other experiments, cell metabolic activity was measured, and no toxicity was observed, even with concentrations of up to 4 mg/mL of magnetic nanoparticles (MNPs). When the cells were treated with magnetic hyperthermia, 80% of cells were dead at 43 °C using 3 mg/mL of MNPs and applying a magnetic field of 530 kHz with 20 kA/m amplitude.

Photocatalytic Degradation of Diclofenac Using Al2O3-Nd2O3 Binary Oxides Prepared by the Sol-Gel Method

This paper reports the sol-gel synthesis of Al2O3-Nd2O3 (Al-Nd-x; x = 5%, 10%, 15% and 25% of Nd2O3) binary oxides and the photodegradation of diclofenac activated by UV light. Al-Nd-based catalysts were analyzed by N2 physisorption, XRD, TEM, SEM, UV-Vis and PL spectroscopies. The inclusion of Nd2O3 in the aluminum oxide matrix in the 10-25% range reduced the band gap energies from 3.35 eV for the γ-Al2O3 to values as low as 3.13-3.20 eV, which are typical of semiconductor materials absorbing in the UV region. γ-Al2O3 and Al-Nd-x binary oxides reached more than 92.0% of photoconverted diclofenac after 40 min of reaction. However, the photocatalytic activity in the diclofenac degradation using Al-Nd-x with Nd2O3 contents in the range 10-25% was improved with respect to that of γ-Al2O3 at short reaction times. The diclofenac photoconversion using γ-Al2O3 was 63.0% at 10 min of UV light exposure, whereas Al-Nd-15 binary oxide reached 82.0% at this reaction time. The rate constants determined from the kinetic experiments revealed that the highest activities in the aqueous medium were reached with the catalysts with 15% and 25% of Nd2O3, and these compounds presented the lowest band gap energies. The experimental results also demonstrated that Nd2O3 acts as a separator of charges favoring the decrease in the recombination rate of electron-hole pairs.

Folate- and glucuronate-functionalization of layered double hydroxides containing dysprosium and gadolinium and the effect on oxidative stress in rat liver mitochondria

Zinc/aluminum layered double hydroxide (LDH) particles were prepared by alkaline precipitation in the presence of dysprosium and dysprosium/gadolinium cations. The particles formed were stable against exchange reactions with folate or glucuronate ions since these organic ions exclusively functionalized the external surface of the layered double hydroxides. While the dysprosium derivatives reached magnetization susceptibilities between 2.06 × 10⁻⁵ and 2.20 × 10⁻⁵ cm³/g, the samples simultaneously containing dysprosium and gadolinium decreased to a range between 1.08 × 10⁻⁵ and 1.73 × 10⁻⁵ cm³/g. This last sample was tested as a magnetic resonance imaging contrast agent and demonstrated a reduction in T1 and T2 relaxation times in a linear dependence with the LDH concentration. The oxidative stress assays in rat liver mitochondria demonstrated the low toxicity of the composition simultaneously containing dysprosium and gadolinium as well as the functionalization product with glucuronate ions, suggesting the potential of these particles to design alternative MRI contrast agents.

A high-resolution frequency variable experimental setup for studying ferrofluids used in magnetic hyperthermia

A scanning system for specific absorption rate of ferrofluids with superparamagnetic nanoparticles is presented in this study. The system contains an induction heating device designed and built with a resonant inverter in order to generate magnetic field amplitudes up to 38 mT, over the frequency band 180-525 kHz. Its resonant circuit involves a variable capacitor with 1 nF of capacitance steps to easily select the desired frequency, reaching from 0.3 kHz/nF up to 5 kHz/nF of resolution. The device performance is characterized in order to compare with the theoretical predictions of frequency and amplitude, showing a good agreement with the resonant inverters theory. Additionally, the setup is tested using a synthetic iron oxide with 10 ± 1 nm diameter suspended in liquid glycerol, with concentrations at 1%. Meanwhile, the temperature rise is measured to determine the specific absorption rate and calculate the dissipated power density for each f. This device is a suitable alternative to studying ferrofluids and analyzes the dependence of the power absorption density with the magnetic field intensity and frequency.

Reconstruction of magnetic source images using the Wiener filter and a multichannel magnetic imaging system

A system for imaging magnetic surfaces using a magnetoresistive sensor array is developed. The experimental setup is composed of a linear array of 12 sensors uniformly spaced, with sensitivity of 150 pT*Hz(-1/2) at 1 Hz, and it is able to scan an area of (16 × 18) cm(2) from a separation of 0.8 cm of the sources with a resolution of 0.3 cm. Moreover, the point spread function of the multi-sensor system is also studied, in order to characterize its transference function and to improve the quality in the restoration of images. Furthermore, the images are generated by mapping the response of the sensors due to the presence of phantoms constructed of iron oxide, which are magnetized by a pulse of 80 mT. The magnetized phantoms are linearly scanned through the sensor array and the remanent magnetic field is acquired and displayed in gray levels using a PC. The images of the magnetic sources are reconstructed using two-dimensional generalized parametric Wiener filtering. Our results exhibit a very good capability to determine the spatial distribution of magnetic field sources, which produce magnetic fields of low intensity.

Superficial magnetic imaging by an xy-scanner of three magnetoresistive channels

A scanning system developed for planar magnetic surfaces composed of a moving line of three magnetoresistive ultrasensitive transducers, complemented by a signal conditioning circuit is presented. After the calibration of the sensors, it was used to determine magnetized surface images with different shapes to evaluate the sensitivity of the device, and the images are represented in gray levels on a scale from 0 to 255 intensities, to get a visual representation of the magnetic field strength. The device is shown to be sensitive enough to detect gradients homogeneities and discontinuities in the magnetic field maps and images of magnetic susceptibility.

An induction heater device for studies of magnetic hyperthermia and specific absorption ratio measurements

The development of a device for generating ac magnetic fields based on a resonant inverter is presented, which has been specially designed to carry out experiments of magnetic hyperthermia. By determining the electric current in the LC resonant circuit, a maximum intensity of magnetic field around of 15 mT is calculated, with a frequency around of 206 kHz. This ac magnetic field is able to heat powdered magnetic materials embedded in biological systems to be used in biomedical applications. Indeed, in order to evaluate the sensitivity of the device we also present the measurements of the specific absorption rate in phantoms performed with commercially prepared Fe(3)O(4) and distilled water at different concentrations.

Characterisation of integrons containing the plasmid-mediated quinolone resistance gene qnrA1 in Klebsiella pneumoniae

The aim of this study was to determine the structural relationships of qnrA1 and other resistance genes in four integrons contained in four clinical isolates of Klebsiella pneumoniae. In the four integrons, the sequences surrounding qnrA1 were similar to those described for pMG252 (accession no. AY070235). The four integrons carried a class 1 integrase gene belonging to the complex class 1 integron. Three of the strains contained an identical integron coding for resistance to beta-lactams, aminoglycosides, chloramphenicol and trimethoprim. The fourth strain contained a different integron coding for resistance to beta-lactams, aminoglycosides and chloramphenicol. Downstream of the last integron, copies of IS6100 and IS26 were present. We describe two new and different integrons containing qnrA1. These integrons code for resistance to different groups of antimicrobial agents from K. pneumoniae clinical strains isolated in the USA.

Mutant prevention concentrations of fluoroquinolones for Enterobacteriaceae expressing the plasmid-carried quinolone resistance determinant qnrA1

The influence of qnrA1 on the development of quinolone resistance in Enterobacteriaceae was evaluated by using the mutant prevention concentration parameter. The expression of qnrA1 considerably increased the mutant prevention concentration compared to strains without this gene. In the presence of qnrA1, mutations in gyrA and parC genes were easily selected to produce high levels of quinolone resistance.

Evaluation of antimicrobial susceptibility of bacteria containing the qnr gene and FOX-5 beta-lactamase by four automated systems

The accuracy and performance of four automated instruments (BD Phoenix, MicroScan WalkAway, VITEK-2 and Wider) were evaluated for susceptibility testing of fluoroquinolones and beta-lactams with four clinical isolates of Klebsiella pneumoniae and the corresponding Escherichia coli transconjugants containing a plasmid carrying the qnr gene and coding for FOX-5 production. No major or very major errors were detected with the MicroScan system. Many of the minor errors for both quinolones and beta-lactams clustered around the intermediate breakpoints.

[Acute correction of nocturnal hypoxemia and sleep pattern using continuous nasal positive pressure in patients with obstructive sleep apnea syndrome]

In order to find out the effectiveness of the nasal CPAP in the treatment of obstructive sleep apnea (OSA), we studied 30 patients with this diagnosis corroborated by nocturnal polysomnography. The average age was 46.37 +/- 11.58 years, 97% were males and 90% were overweight, with a weight of 101.24 +/- 15.57 Kg. All the patients were evaluated before and after the application of nasal CPAP with a pressure of 12.9 +/- 4.35 cm of H2O with a FIO2 of 21%. The sleep efficiency index improved from 0.62 +/- 0.03 to 0.84 +/- 0.02 (p < 0.0001). The maximum duration of the apneas diminished from 65.5 +/- 6.5 seconds to 19 +/- 3.7 seconds (p < 0.0001), and the minimum level of O2 saturation of the hemoglobin increased from 56.8 +/- 3.2% to 84.9 +/- 1.9% (p < 00.0001). These findings showed a clear improvement in the majority of the evaluated parameters in all of the patients, and, in many of them, a normalization. We conclude that the nasal CPAP is effective for the acute improvement of the disorders observed during the sleep in patients with OSA, which supports its therapeutic use in this illness.