Chemical, magnetic and electronic properties of NaxCoO2 and related compounds

In the last years, NaxCoO2 has experienced a renewed interest in the field of solid state science. However, NaxCoO2 is not a novel material, it has been extensively studied for decades. In the 80´s, it was investigated due to its electrochemical properties (high ionic mobility, high electrical conduction) and tested as a cathod in reversible alkaline cells, as its analogous LixCoO2. In the 90’s, its thermoelectric properties raised the interest of this material for energy harvesting at high temperature and refrigeration. However, the discovery of novel properties (i.e. high thermoelectric power or, mainly, the occurrence of superconductivity below 5K) and their possible relationship with similar phenomena found in other materials boosted a renewed interest in this highly electronic correlated system. The structural, magnetic and electronic properties of NaxCoO2 have been studied in detail in order to understand deeply some of the most fundamental aspects which drive the chemical and physical behaviour of this system: presence of oxygen vacants, the role of water played in the occurrence of superconductivity, the proximity of the system to a quantum phase transition or the nature of the unconventional thermoelectric and magnetic properties with x, specifically at the half-doped x=0.5. All of them are kept under strong scientific discussions that, far from solving them, contribute to generate an even higher controversy. On other hand, the efficiency of topotactic reactions in order to exchange Na+ ions by other mono- or di-valent ions, such as Li+, Ca2+ or Sr2+, has been studied. The physical properties of the resulting compounds are shown and compared to those ones from the analogous NaxCoO2 precursor. Therefore, in the pages inside, the reader will can find our main results and conclusions achieved in each one of these subjects, in a modest attempt to explain the chemistry and physics involved in NaxCoO2 and related compounds

Informe sobre cuestiones marítimas, transfronterizas y otros problemas jurídicos

Traballo fin de grao (UDC.DER). Dereito. Curso 2013/201

Hyperthermia produced by magnetic nanoparticles as an alternative method to control a major foodborne pathogen

NanoSpain 2017Salmonella enterica is responsible for the majority of the reported foodborne outbreaks, and that is why it is considered one of the most important foodborne pathogens nowadays [1]. Like many others bacteria, S. enterica can survive disinfection and resist a wide variety of biocidal agents [2]. Nowadays, the synthesis of superparamagnetic nanoparticles (MNPs) and its application in magnetic hyperthermia (MH) is of great interest, with MH being recently reported as a viable alternative to traditional disinfection methods against bacteria [3]. However, fundamental studies comprising the MH effect on different populations of planktonic cells and biofilm cells are scarce. Therefore, this work aimed at evaluating the effect of MH on different populations of planktonic cells and biofilms of S. enterica. The work was performed using a S. enterica collection strain (NCTC 13349), which different planktonic cell populations (lag, exponential, and stacionary phase) were adjusted to a final concentration of 1 × 108 cells/ml, while biofilms were formed in silicone coupons. Samples containing both magnetite nanoparticles and S. enterica cells or biofilms have been subjected to an alternating magnetic field of chosen amplitude 100 Oe with frequency of 873 kHz until different temperatures were reached. In order to evaluate the bactericidal effect of MH, survival of planktonic and biofilm cells was determined by colony forming unit (CFU) enumeration. Based on the most relevant results, cell membrane integrity and the effects of MH on cells surface and biofilm structure were analysed through microscopy techniques. Results showed that the high structural-magnetic quality magnetite nanoparticles used were effective against all planktonic cell populations and biofilms under an oscillating magnetic field. In fact, MNPs-based hyperthermia was able to promote a significant cell viability reduction on all planktonic cell populations both bacterial lyfe styles. Nonetheless, planktonic cells were more tolerant to MH than biofilms, possibly due to diffusion limitations along these bacterial communities. Microscopy images of planktonic cells and biofilms showed that MH can affect cell membrane integrity as well as the biofilms structure. In conclusion, this work presents evidences of the bactericidal effect of MH produced by MNPs against S. enterica, both regarding planktonic populations and biofilms. This ability of MH to control a major foodborne pathogen constitutes a novel contribution to the finding of new useful applications of hyperthermia.info:eu-repo/semantics/publishedVersio

Development of magnetically active scaffolds for bone regeneration

This work reports on the synthesis, with the thermally induced phase separation (TIPS) technique, of poly (L-lactide) (PLLA) scaffolds containing Fe-doped hydroxyapatite (FeHA) particles for bone regeneration. Magnetization curves and X-ray diffraction indicate two magnetic particle phases: FeHA and magnetite Fe3O4. Magnetic nanoparticles (MNPs) are approximately 30 ± 5 nm in width and 125 ± 25 nm in length, and show typical ferromagnetic properties, including coercivity and rapid saturation magnetization. Scanning electron microscopy (SEM) images of the magnetic scaffolds reveal their complex morphology changes with MNP concentration. Similarly, at compositions of approximately 20% MNPs, the phase separation changes, passing from solid–liquid to liquid–liquid as revealed by the hill-like structures, with low peaks that give the walls in the SEM images a surface pattern of micro-ruggedness typical of nucleation mechanisms and growth. In vitro degradation experiments, carried out for more than 28 weeks, demonstrated that the MNPs delay the scaffold degradation process. Cytotoxicity is appreciated for FeHA content above 20%.This work was supported by the University of The Basque Center and the Portuguese Foundation for Science and Technology (FCT) under the framework Strategic Funding UID/FIS/04650/ UID/BIA/04050/2013, and UID/BIO/04469. S.R. would like to the FCT for the SFRH/BD/111478/2015 grant. The authors acknowledge funding by the Spanish Ministry of Economy and Competitiveness (MINECO) under the project MAT2016-76039-C4-3-R (AEI/FEDER, UE)info:eu-repo/semantics/publishedVersio

Magnetic solid nanoparticles and their counterparts: recent advances towards cancer theranostics

Cancer is currently a leading cause of death worldwide. The World Health Organization estimates an increase of 60% in the global cancer incidence in the next two decades. The inefficiency of the currently available therapies has prompted an urgent effort to develop new strategies that enable early diagnosis and improve response to treatment. Nanomedicine formulations can improve the pharmacokinetics and pharmacodynamics of conventional therapies and result in optimized cancer treatments. In particular, theranostic formulations aim at addressing the high heterogeneity of tumors and metastases by integrating imaging properties that enable a non-invasive and quantitative assessment of tumor targeting efficiency, drug delivery, and eventually the monitoring of the response to treatment. However, in order to exploit their full potential, the promising results observed in preclinical stages need to achieve clinical translation. Despite the significant number of available functionalization strategies, targeting efficiency is currently one of the major limitations of advanced nanomedicines in the oncology area, highlighting the need for more efficient nanoformulation designs that provide them with selectivity for precise cancer types and tumoral tissue. Under this current need, this review provides an overview of the strategies currently applied in the cancer theranostics field using magnetic nanoparticles (MNPs) and solid lipid nanoparticles (SLNs), where both nanocarriers have recently entered the clinical trials stage. The integration of these formulations into magnetic solid lipid nanoparticles—with different composition and phenotypic activity—constitutes a new generation of theranostic nanomedicines with great potential for the selective, controlled, and safe delivery of chemotherapy.This research was funded by the Portuguese Foundation for Science and Technology (Fundação para a Ciência e a Tecnologia—FCT) and the European Regional Development Fund (ERDF) through NORTE 2020 (2014–2020 North Portugal Regional Operational Program) under the project NORTE-01-0145-FEDER-031142 “Local specific treatment of triple-negative-breast-cancer through externally triggered target-less drug carriers (MagtargetON)”, and by 2014–2020 INTERREG Cooperation Programme Spain–Portugal (POCTEP) through the project 0624_2IQBIONEURO_6_E

Pseudomonas aeruginosa PAO 1 in vitro timekill kinetics using single phages and phage formulationsmodulating death, adaptation, and resistance

Pseudomonas aeruginosa is responsible for nosocomial and chronic infections in healthcare settings. The major challenge in treating P. aeruginosa-related diseases is its remarkable capacity for antibiotic resistance development. Bacteriophage (phage) therapy is regarded as a possible alternative that has, for years, attracted attention for fighting multidrug-resistant infections. In this work, we characterized five phages showing different lytic spectrums towards clinical isolates. Two of these phages were isolated from the Russian Microgen Sextaphage formulation and belong to the Phikmvviruses, while three Pbunaviruses were isolated from sewage. Different phage formulations for the treatment of P. aeruginosa PAO1 resulted in diversified timekill outcomes. The best result was obtained with a formulation with all phages, prompting a lower frequency of resistant variants and considerable alterations in cell motility, resulting in a loss of 73.7% in swimming motility and a 79% change in swarming motility. These alterations diminished the virulence of the phage-resisting phenotypes but promoted their growth since most became insensitive to a single or even all phages. However, not all combinations drove to enhanced cell killings due to the competition and loss of receptors. This study highlights that more caution is needed when developing cocktail formulations to maximize phage therapy efficacy. Selecting phages for formulations should consider the emergence of phage-resistant bacteria and whether the formulations are intended for short-term or extended antibacterial application.This study was supported by the Portuguese Foundation for Science and Technology (FCT) under the scope of the strategic funding of UID/BIO/04469/2020 unit. S.S. acknowledges funding by FCT through the individual scientific employment program contract (2020.03171.CEECIND).info:eu-repo/semantics/publishedVersio

Control of bacterial cells growths by magnetic hyperthermia

In this work, we report the effectiveness of magnetic hyperthermia as a potential disinfection method against food spoilage microorganisms. High structural-magnetic quality magnetite nanoparticles have been found to be effective against bacterial microorganisms in solution under an oscillating magnetic field. Samples containing both magnetite nanoparticles and Pseudomonas fluorescens cells in aqueous solution have been subjected to an alternating magnetic field of chosen amplitude 100 Oe with frequency of 873 kHz for different times, achieving different maximum temperatures ranging from 35°C to 55°C. The subsequent colony forming units count evidenced an important decreasing of the cell survival with temperature in comparison to a conventional direct heating, ending in the total eradication of the microorganisms in relatively short times (~8 min). This ability of magnetic hyperthermia to control bacteria cells constitutes a novel contribution to the finding of new useful applications of hyperthermia different from biomedicine.This work was supported in part by the European Community’s under the FP7-Cooperation Programme through the MAGISTER project “Magnetic Scaffolds for in vivo Tissue Engineering” Large Collaborative Project FP7 and from European Regional Development Fund (ERDF) under the Northern Regional Operational Programme ON.2-O Novo Norte- for the acquisition of the main equipment used in this research. D. R. also acknowledges the financial support of Portuguese Foundation for Science and Technology (FCT) through the grant SFRH/BPD/72632/2010

Solid Lipid Particles for Lung Metastasis Treatment

Solid lipid particles (SLPs) can sustainably encapsulate and release therapeutic agents over long periods, modifying their biodistribution, toxicity, and side effects. To date, no studies have been reported using SLPs loaded with doxorubicin chemotherapy for the treatment of metastatic cancer. This study characterizes the effect of doxorubicin-loaded carnauba wax particles in the treatment of lung metastatic malignant melanoma in vivo. Compared with the free drug, intravenously administrated doxorubicin-loaded SLPs significantly reduce the number of pulmonary metastatic foci in mice. In vitro kinetic studies show two distinctive drug release profiles. A first chemotherapy burst-release wave occurs during the first 5 h, which accounts for approximately 30% of the entrapped drug rapidly providing therapeutic concentrations. The second wave occurs after the arrival of the particles to the final destination in the lung. This release is sustained for long periods (>40 days), providing constant levels of chemotherapy in situ that trigger the inhibition of metastatic growth. Our findings suggest that the use of chemotherapy with loaded SLPs could substantially improve the effectiveness of the drug locally, reducing side effects while improving overall survival.This research was funded by the European Regional Development Fund (ERDF) and the Spanish MINECO Refs. PI16/00496 (AES 2016), PI19/00349 (AES 2019), and DTS19/00033; IDIVAL Refs. INNVAL17/11 and INNVAL19/12. J.G. and M.B.-L. also acknowledge financial support from the Fundação para a Ciência e a Tecnologia and the ERDF through NORTE2020 (2014–2020 North Portugal Regional Operational Program) through the projects UTAP-EXPL/NTec/0038/2017 (NANOTHER) and NORTE-01-0145-FEDER-031142 (MAGTARGETON). Nano2clinics COST Action CA17140

Enhanced performance of cobalt ferrite encapsulated in graphitic shell by means of AC magnetically activated catalytic wet peroxide oxidation of 4-nitrophenol

Here we report preliminary catalytic wet peroxide oxidation (CWPO) experiments performed in the presence of an alternating current (AC) magnetic field. One ferromagnetic graphitic nanocomposite – composed by a cobalt ferrite core and a graphitic shell (CoFe2O4/MGNC), was employed in the process, here named magnetically activated catalytic wet peroxide oxidation (MA-CWPO). An aqueous solution containing 5.0 g L−1 of 4-nitrophenol (4-NP) to simulate a high strength polluted stream was used as model system. The experiments were performed at room temperature and atmospheric pressure, with stoichiometric amount of hydrogen peroxide (H2O2), pH=3 and CoFe2O4/MGNC catalyst load=5.0 g L−1 (corresponding to a 4-NP/CoFe2O4 mass ratio of 6.9, as CoFe2O4 accounts for 14.4 wt% of CoFe2O4/MGNC). It was shown that the performance of CWPO is enhanced upon application of an AC magnetic field (frequency of 533.9 kHz and magnitude of 240 G). As a result, high 4-NP mineralization was obtained by MA-CWPO (as reflected by a total organic carbon abatement of 79% after 4 h of reaction, instead of 39% in the absence of a magnetic field). This positive effect was ascribed to the localised increase of CoFe2O4/MGNC surface temperature resulting from heat release upon exposure of the nanoparticulated catalyst to an AC magnetic field, which accelerates the catalytic decomposition of H2O2 via hydroxyl radicals (HO%) formation.info:eu-repo/semantics/publishedVersio