Calcium phosphates are biomaterials widely used in bone tissue engineering. In recent years, the alternative of obtaining these materials with antimicrobial properties, has been explored due to the multiple advantages that this would imply in the design of devices or implants that prevent the failure of these associated with bacterial colonization. The goal of the present work was obtaining gold nanoparticles supported on biphasic calcium phosphates (BCPs) with high crystallinity by one-step solution combustion technique, and with antimicrobial response, a fact that can significantly reduce the production cost of these materials. X-ray diffractograms (XRD) showed that prepared powders have high crystallinity owing to high temperatures during the combustion reaction, also Rietveld refinement showed that the inclusion of gold nanoparticles (AuNPs) influenced the phases’ ratio obtained. Furthermore, scanning electron microscopy (SEM) showed agglomeration of particles with morphologies with shape tending to be equigranular, while the presence of AuNPs was corroborated by transmission electron microscopy (TEM). All samples that were obtained in a single step, by solution combustion, showed antimicrobial behavior validated through the inhibition halos, whereas particles subjected to thermal treatment lost their antimicrobial response. Resumen Los fosfatos de calcio son biomateriales ampliamente usados en ingeniería de tejido óseo. En los últimos años, la alternativa de obtener estos materiales con propiedades antimicrobianas ha sido explorada debido a las múltiples ventajas que presentan en el diseño de dispositivos o implantes que incluyan la prevención de fallas asociadas a la colonización bacteriana. El principal objetivo de esta investigación fue obtener nanopartículas de oro soportadas en fosfatos de calcio bifásicos bien cristalizados en una sola etapa mediante la técnica de combustión de soluciones y con respuesta antimicrobiana, un hecho que puede significar la reducción del coste de producción de estos materiales. Los difractogramas de rayos X evidenciaron que los polvos preparados presentaron una alta cristalinidad debido a las altas temperaturas durante la reacción de combustión. El refinamiento Rietveld mostró que la inclusión de las nanopartículas de oro influenciaron la relación de las fases obtenidas. La microscopia electrónica de barrido mostró la aglomeración de partículas con morfologías tendentes a ser equigranulares. La presencia de nanopartículas de oro fue corroborada mediante microscopia electrónica de transmisión. Todas las muestras que fueron obtenidas en un solo paso mediante la combustión de soluciones mostraron un comportamiento antimicrobiano validado a través de halos de inhibición, mientras que, en las partículas sometidas a tratamiento térmico, este comportamiento estuvo ausente.

In this study, for the first time, caffeine and citrulline were used as fuels for the synthesis of the spinel ferrite CoFe2O4 by gel combustion. The influence of the oxidizer to fuel molar ratio (φ) on the synthesis of cobalt ferrite was studied. X-Ray Diffraction (XRD) showed that the spinel phase was obtained in all the combustions, but the use of caffeine as fuel allowed it to be obtained with high purity, while in the other combustions CoO appeared as a secondary phase due to changes in the reaction. Furthermore, the crystallite size was estimated using the Scherrer equation and considering the plane (311), finding it to be in the range of 32–40 nm, and increasing as the amount of fuel was increased. In addition, the adiabatic flame temperatures were estimated, finding that, in the synthesis with φ = 0.7, the flame temperatures were 1974 K and 1711 K, for the caffeine and citrulline respectively, which could be sufficient to obtain the phase in one stage. The ignition temperatures identified by DSC/TG thermal analysis for caffeine and citrulline samples with φ = 1.0 were 297 and 191 °C, respectively, which are in the range of traditional fuels. The morphology was studied by scanning electron microscopy (SEM) and transmission electron microscopy (TEM) which revealed that the particles were agglomerated as a result of high reaction temperatures. The magnetic properties identified by the vibrating sample magnetometer (VSM) for the sample with caffeine and ratio φ = 0.7 were saturation magnetization Ms = 95.16 emu g−1, coercivity field Hc = 710.76 Oe and remanent magnetization Mr = 44.86 emu g−1. Meanwhile, with citrulline and ratio φ = 0.7, the properties were saturation magnetization Ms = 59.14 emu g−1, coercivity field Hc 837.15 Oe and remanent magnetization Mr = 32.30 emu g−1. It should be pointed out that the high saturation magnetization values obtained with caffeine fuel exceed those reported with traditional fuels. The obtained results allow us to infer that these fuels could be used as alternatives in synthesizing inorganic oxides by combustion in one step.

Flubendazole (FBZ) is a poorly water-soluble drug, and different methodologies have been proposed to improve its oral bioavailability. Obtaining the amorphous drug phase is an alternative to improve its water solubility. Several techniques for drug amorphization, such as spray drying, lyophilization, melt quenching, solvent-evaporation, and ball milling, can yield various types of structural disorder and possibly render variations in physicochemical properties. Herein, we focus on evaluating the influence of the ball-milling process on the amorphization of FBZ. The characterization of the average global and local structures before, during, and after the milling process is described by sequential Rietveld refinements, pair distribution function analysis, and the Reverse Monte Carlo method. We show that preserving the local structure (nearest molecules) can be responsible for avoiding the fast structure recrystallization commonly observed when using the solvent-evaporation process for the studied drug.

Structural, morphological, magnetic, and electrical properties of the challenging Sr1-xBaxMnO3 (x=0, 0.4) manganite are discussed. Polycrystalline Sr1-xBaxMnO3 samples were prepared via the standard solid-state reaction. Conventional X-ray diffraction and synchrotron radiation measurements showed the hexagonal structure (space group P63/mmc) of the samples. The stability of the hexagonal symmetry of Sr0.6Ba0.4MnO3 persisted up to 120 K. This result, along with the fact that the space group P63/mmc is centrosymmetric, discounted the possibility of having a long-range ferroelectric ordering. Pristine SrMnO3 samples exhibited an antiferromagnetic transition at a Néel temperature ∼280 K. In turn, Sr0.6Ba0.4MnO3 showed two transitions at ∼325 K and ∼270 K. Measurements of the electrical polarization versus the electric field showed closed loops, although visually distinct from those of a true ferroelectric material. Hence it was evident that spurious effects caused the polarization curves that resembled ferroelectric loops. Resistivity measurements on Sr0.6Ba0.4MnO3 showed the insulating nature of these samples.

The FDA-approved anthelmintic flubendazole has shown potential to be repositioned to treat cancer and dry macular degeneration; however, its poor water solubility limits its use. Amorphous solid dispersions may overcome this challenge, but the balance of excipients may impact the preparation method and drug release. The purpose of this study was to evaluate the influence of adjuvants and drug loading on the development of an amorphous solid dispersion of flubendazole-copovidone by hot-melt extrusion. The drug, copovidone, and adjuvants (magnesium stearate and hydroxypropyl cellulose) mixtures were statistically designed, and the process was performed in a twin-screw extruder. The study showed that flubendazole and copovidone mixtures were highly extrudable, except when drug loading was high (>40%). Furthermore, magnesium stearate positively impacted the extrusion and was more effective than hydroxypropyl cellulose. The extruded materials were evaluated by modulated differential scanning calorimetry and X-ray powder diffraction, obtaining positive amorphization and physical stability results. Pair distribution function analysis indicated the presence of drug-rich domains with medium-range order structure and no evidence of polymer-drug interaction. All extrudates presented faster dissolution (HCl, pH 1.2) than pure flubendazole, and both adjuvants had a notable influence on the dissolution rate. In conclusion, hot-melt extrusion may be a viable option to obtain stable flubendazole:copovidone amorphous dispersions.

We investigate the local atomic structure of verapamil hydrochloride in the amorphous state (a-VRPH) using the pair distribution function (PDF) and Reverse Monte Carlo (RMC) methods. We obtain the a-VRPH sample from its crystalline counterpart (c-VRPH) using the solvent evaporation technique. From the measured X-ray powder diffraction (XRPD) data for a-VRPH and c-VRPH, two total structure factors S(Q) are derived, and Fourier transforming them, two total reduced distribution functions, γ(R), are obtained. We refine the XRPD pattern of c-VRPH using the Rietveld method to confirm the sample's crystal structure is the pure c-VRPH. The partial Sij(Q) factors and PDF functions are simulated based on the VRPH crystal structure found in the Cambridge Structural Database® (CSD). The PDF and RMC analyses allow us to observe some similarities between a-VRPH and c-VRPH at the intramolecular level and the main differences at the intermolecular level induced by the amorphization process.

Calcium carbonate (CaCO3) from the seaweed Lithothamnium calcareum is a suitable dietary supplement for the prevention of osteoporosis, due to its chemical composition. This study compared CaCO3 from L. calcareum to CaCO3 from oyster shell and inorganic minerals that are already used in the pharmaceutical industry. The Rietveld refinement of the XRD showed that the mineral fraction of L. calcareum is composed of aragonite (50.3 wt%), magnesian calcite (45.3 wt%), calcite (4.4 wt%), comin contrast to oyster shell and inorganic minerals, which contain only calcite. The morphology of L. calcareum carbonate particles is granular xenomorphic, which is distinct from the scalenohedral form of inorganic calcite and the fibrous and scale-like fragments of oyster shell. The crystal structures of aragonite and magnesian calcite, present in L. calcareum, have higher contents of oligoelements than the pure calcite in other materials. The isotopic composition (stable isotopes of carbon and oxygen) is heavy in the CaCO3 from L. calcareum (δ13C = 1.1‰; δ18O = −0.1‰) and oyster shell (δ13C = −4‰; δ18O = −2.8‰) in marked contrast to the much lighter isotopic composition of inorganic mineral CaCO3 (δ13C = −19.2‰; δ18O = −26.3‰). The differences indicated above were determined through principal component analysis, where the first and second principal components are sufficient for the clear distinction and traceability of CaCO3 sources.

The levitation of samples in an acoustic field has been of interest in the preparation and study of amorphous solid dispersions (ASD). Here, niclosamide-polymer solutions were levitated in a multi-emitter single-axis acoustic levitator and analyzed for 10 min at a High-resolution synchrotron X-ray powder diffraction beamline. This assembly enabled high-quality and fast time-resolved measurements with microliter sample size and measurement of solvent evaporation and recrystallization of niclosamide (NCL). Polymers HPMCP-55S, HPMCP-50, HPMCP-55, Klucel®, and poloxamers were not able to form amorphous dispersions with NCL. Plasdone® and Soluplus® demonstrated excellent properties to form NCL amorphous dispersions, with the last showing superior solubility enhancement. Furthermore, this fast levitation polymer screening showed good agreement with results obtained by conventional solvent evaporation screening evaluated for five days in a stability study, carried out at 40 °C/75% RH. The study showed that acoustic levitation and high-resolution synchrotron combination opens up a new horizon with great potential for accelerating ASD formulation screening and analysis.

We use X-ray pair distribution function (PDF) analysis applied to high-energy synchrotron X-ray powder diffraction data to evaluate the amorphous solid dispersions interactions and their aging stability. The obtained systems are based on hydroxypropyl methylcellulose (hypromellose) derivatives and flubendazole (FBZ) drug dispersions prepared using a spray-dryer technique. We carry out stability studies under aging parameters (40 °C/75% relative humidity) to tune the systems’ recrystallization. The results reveal that ion-base interactions between the drug-polymer matrix are responsible for reducing clustering processes yielding slower recrystallization and different ordering in the hypromellose phthalate (HPMCP/FBZ) and hypromellose acetate succinate (HPMC-AS/FBZ) systems and complete drug clustering in hypromellose (HPMC-E3/FBZ). The structural ordering was accessed using differential X-ray PDFs that revealed the region between 3.5 Å and 5.0 Å could be related to FBZ intermolecular interactions and is more ordered for the least stable system (HPMC-E3/FBZ) and less ordered for the most stable system (HPMCP/FBZ). These results show that the ion-base interactions between drug and matrix occur at these intermolecular distances.

In this study, CaCu3Ti4O12 ceramic composites were prepared through solid-state reaction by adding Sr2+ and removing Cu2+. Application of the Rietveld method and structure refinement revealed the presence of pure CaCu3Ti4O12 (CCTO) phase for x = 0.00 and Sr0.75Ca0.25TiO3 (SCTO) phase for sample x = 3.00. The other samples presented a mixture of both phases. The sample microstructures showed that increasing the amount of SCTO phase led to the formation of cubic CCTO grains. The x = 0.15 sample presented giant dielectric permittivity results, 3.28 × 105, associated with increased grain size and greater grain boundary capacitance, thus indicating it could be a promising material for class III capacitors. On the other hand, greater presence of the SCTO phase displayed potential non-ohmic behavior, as seen with sample x = 2.70, which has a high nonlinear coefficient (α ∼ 30.0) and low current leakage, (IL ∼ 9.0 μA).