Comparative Structural and Optical Properties of Different Ceria Nanoparticles

Herein a comparative study of five nanocrystalline cerium oxides (CeO2-delta) synthesised by different methods and calcined at 500 degrees C is reported. XRPD analysis showed that stoichiometry parameter delta, crystallite size/strain and lattice constant were only slightly affected by the method utilized. All ceria nanoparticles are nearly spherical in shape with faceted morphology, free of defects and with a relatively uniform size distribution. The average microstrain was found to be approximately 10 times higher than that of bulk counterpart. The absorption edge of nanocrystalline materials was shifted towards a higher wavelengths (red shift) in comparison with bulk counterpart, and band gap values were in the range 2.7-3.24 eV (3.33 eV for bulk counterpart)

BCG hydrogel promotes CTSS-mediated antigen processing and presentation, thereby suppressing metastasis and prolonging survival in melanoma.

BACKGROUND The use of intralesional Mycobacterium bovis BCG (intralesional live BCG) for the treatment of metastatic melanoma resulted in regression of directly injected, and occasionally of distal lesions. However, intralesional-BCG is less effective in patients with visceral metastases and did not significantly improve overall survival. METHODS We generated a novel BCG lysate and developed it into a thermosensitive PLGA-PEG-PLGA hydrogel (BCG hydrogel), which was injected adjacent to the tumor to assess its antitumor effect in syngeneic tumor models (B16F10, MC38). The effect of BCG hydrogel treatment on contralateral tumors, lung metastases, and survival was assessed to evaluate systemic long-term efficacy. Gene expression profiles of tumor-infiltrating immune cells and of tumor-draining lymph nodes from BCG hydrogel-treated mice were analyzed by single-cell RNA sequencing (scRNA-seq) and CD8+ T cell receptor (TCR) repertoire diversity was assessed by TCR-sequencing. To confirm the mechanistic findings, RNA-seq data of biopsies obtained from in-transit cutaneous metastases of patients with melanoma who had received intralesional-BCG therapy were analyzed. RESULTS Here, we show that BCG lysate exhibits enhanced antitumor efficacy compared to live mycobacteria and promotes a proinflammatory tumor microenvironment and M1 macrophage (MΦ) polarization in vivo. The underlying mechanisms of BCG lysate-mediated tumor immunity are dependent on MΦ and dendritic cells (DCs). BCG hydrogel treatment induced systemic immunity in melanoma-bearing mice with suppression of lung metastases and improved survival. Furthermore, BCG hydrogel promoted cathepsin S (CTSS) activity in MΦ and DCs, resulting in enhanced antigen processing and presentation of tumor-associated antigens. Finally, BCG hydrogel treatment was associated with increased frequencies of melanoma-reactive CD8+ T cells. In human patients with melanoma, intralesional-BCG treatment was associated with enhanced M1 MΦ, mature DC, antigen processing and presentation, as well as with increased CTSS expression which positively correlated with patient survival. CONCLUSIONS These findings provide mechanistic insights as well as rationale for the clinical translation of BCG hydrogel as cancer immunotherapy to overcome the current limitations of immunotherapies for the treatment of patients with melanoma

Size effects in the magnetic behaviour of TbAl_2 milled alloys

The study of the magnetic properties depending upon mechanical milling of the ferromagnetic polycrystalline TbAl_2 material is reported. The Rietveld analysis of the X-ray diffraction data reveals a decrease of the grain size down to 14 nm and -0.15 % of variation of the lattice parameter, after 300 hours of milling time. Irreversibility in the zero field cooled - field cooled (ZFC-FC) DC-susceptibility and clear peaks in the AC susceptibility between 5 and 300 K show that the long-range ferromagnetic structure is inhibited in favour of a disordered spin arrangement below 45 K. This glassy behaviour is also deduced from the variation of the irreversibility transition with the field (H^{2/3}) and frequency. The magnetization process of the bulk TbAl_2 is governed by domain wall thermal activation processes. By contrast, in the milled samples, cluster-glass properties arise as a result of cooperative interactions due to the substitutional disorder. The interactions are also influenced by the nanograin structure of the milled alloys, showing a variation of coercivity with the grain size, below the crossover between the multi- and single-domain behaviours.Comment: 23 pages, 11 figures, to appear in J. Phys.: Condens. Ma

Cation distribution and size-strain microstructure analysis in ultrarine Zn-Mn ferrites obtained from acetylacetonato complexes

The ultrafine ZnFe2O4, MnFe2O4, and cation deficit Zn-Mn ferrites were obtained by thermal decomposition of appropriate mixed complex compounds with acetylacetone (2,4-pentadione) ligands ([M(AA),]) at 500 degreesC. In ZnFe2O4 cation distribution is partially inverse with 14% of Zn2+ ions at octahedral 16d sites, while MnFe2O4 is a normal spinel. Cation distribution in nonstoichiometric (Zn,Mn,Fe)(3-delta)O-4 (delta = 0.18-0.30) is found to be (Zn(x)Mn(y)square(epsilon))(8a)[Fe(z)square(v)](16d), with a random distribution of vacancies. Nonstoichiometry in Zn-Mn ferrites is accompanied by a cation valence change, i.e., partial oxidation of Mn2+ to Mn4+. Microstructure size-strain analysis shows isotropic X-ray line broadening due to the crystallite size effect and anisotropic X-ray line broadening due to the crystallite strain effect. In binary ferrites anisotropic X-ray line broadening due to the strain effect is higher in ZnFe2O4 than in MnFe2O4, while in ternary cation-deficient Zn-Mn ferrites it decreases as the vacancy concentration delta increases

Carboxylic acids and polyethylene glycol assisted synthesis of nanocrystalline nickel ferrites

Different synthesis methods for the preparation of nanocrystalline nickel ferrites are reported: the thermal decomposition of precursors, made of: (i) metal-nitrate salts with carboxylic acids (citric, malonic and tartaric), and (ii) metal-nitrate salts and polyethylene glycol (PEG), in the presence of potassium chloride as a capping agent. The as-prepared gel precursors were characterized by TGA/DTA, while the samples obtained after annealing at 450 degrees C were investigated by FTIR, FESEM, XRD and Mossbauer spectroscopy. Regardless of the type of carboxylic acid used, nanocrystallites prepared by (i) method are similar in size (11-16 nm), while the method (ii) gives crystallites similar to 33 nm in size with negligible microstrain. The differences in the lattice parameter, ranging from 8.3369(2) to 8.3574(2) angstrom, result from cation distribution, nonstoichiometry and structural imperfections in the nickel ferrite nanoparticles. The Mossbauer spectra analysis indicates existence of large distortions of tetrahedral and octahedral sites in these spinel compounds. (C) 2013 Elsevier Ltd and Techna Group S.r.l. All rights reserved

The dependence of cation distribution, microstrain and magnetic susceptibility on particle size in nanocrystalline Gd2O3/Y2O3

A novel synthesis route based on thermal decomposition of yttrium and gadolinium complexes with 2,4-pentanedione ligand has been used to synthesize 5 nn size (Y0.9Gd0.1)(2)O-3 powder. Refinement of occupancy parameters revealed that Gd3+ ions preferably occupy C-3i sites in host Y2O3, forming a material with a metastable cation distribution. The average crystallite size was found to increase, and the average microstrain to decrease, as the annealing temperature is increased, while the Gd3+ ion distribution remained metastable in nature. Small anisotropic X-ray powder diffraction pattern line broadening due to crystallite size effects was observed. The inverse susceptibility of the 5 nn sample exhibits unusual break in slope to a smaller value below 2.7 K. (C) 2007 Acta Materialia Inc. Published by Elsevier Ltd. All rights reserved

Formation of nanosize Li-ferrites from acetylacetonato complexes and their crystal structure, microstructure and order-disorder phase transition

Nanosize Li-ferrites were synthesised by the thermal decomposition of an appropriate mixture of complex compounds with acetylacetone - (2,4 pentadione) ligands ([M(AA)(x)]; M = Li and Fe) at 500 degrees C. The obtained sample is composed of three phases determined by the standard Rietveld procedure: Li0.5Fe2.5O4 (S. G. P4(3)32), Li1.16Fe3O4 (S.G. Fd (3) over barm) and LiFeO2 (S.G. Fm (3) over barm). Cation distribution in nanosize ordered spinel Li0.5Fe2.5O4 deviates from that of the bulk counterpart. Microstructure parameters (crystallite size of similar to 23 nm and strain of 3.2526(9) x 10(3)) were determined by the Rietveld refinement of the TCH-pV parameters. SEM microphotographs show a particle size of similar to 50-60 nm. An order disorder phase transition in ordered spinel Li0.5Fe2.5O4 was studied by DSC measurements and in situ XRPD technique. The temperature of phase transition was found to be 762 degrees C ( DSC) and (745 +/- 5) degrees C ( XRPD)

Synthesis and crystal structure of hexaaquamagnesium hydrogen phosphododecatungstate tetrahydrate [Mg(H20)6][HPW12040]4H20

International audienceCrystals suitable for X-ray structure analysis were obtained after the slow evaporation of the reaction mixture containing equimolar quantities of magnesium chloride and dodecatungstophosphoric acid aqueous solution insuring pH of the solution between 1.0 and 1.2. This simple synthetic route yielded stability of Keggin anion and high quality [Mg(H2O)6][HPW12O40]·4H2O single crystals. The obtained compound belongs to the group of heteropoly compounds and its structure is composed of Keggin [PW12O40]3– anions, [Mg(H2O)6]2+ cations and lattice water molecules. Zigzag arrangement of Keggin anions along c-axis creates irregular channels occupied by [Mg(H2O)6]2+ cations and lattice H2O molecules. The calculation of the total potential solvent volume indicated the presence of 4.1 lattice H2O lattice molecules per formula unit, which is in agreement with the here presented structural model. The position of one lattice water molecule is well defined, while each of three other molecules is statistically distributed over two locations. Hydrogen bonds involve all coordinated and lattice H2O molecules, as well as some oxygen atoms from the Keggin anion

Investigation of nanocrystalline phases in Li-La-Fe-O system formed by the decomposition of acetylacetonato complexes

Applying a new synthesis route based on the thermal decomposition of a mixture acetylacetonato complexes, Li(AA), La(AA)(3) and Fe(AA)(3), Li, La ferrite (Li0.5La0.08Fe2.42O4) was formed. The element analysis performed by ICP technique and the Rietveld refinement data indicate that the sample is composed of three phases: Li0.5La0.008Fe2.42O4 (69%, SG P4(3)32, a = 8.3445(3) angstrom), La0.14Fe3O4 (16%, SG Fd (3) over barm, a = 8.403(1) angstrom) and LiFeO2 (15%, SG Fm (3) over barm, a = 4.2291(8) angstrom). A partial substitution Fe3+ - gt La3+ in Li ferrite and La insertion at 16c site in Fe3O4 occur at low concentrations. A partial cation ordering at 4b and 12d octahedral sites in Li0.5La0.08Fe2.42O4 was noticed. TEM micrograph shows that the nanoparticles are spherically shaped and that the particle distribution is in the range between 7 and 33 nm. The sample exhibits superparamagnetic behavior, thus the composite has potential industrial applications. (c) 2006 Elsevier B.V. All rights reserved