ZrO2–ZnO Nanoparticles as Antibacterial Agents

https://pubs.acs.org/doi/abs/10.1021/acsomega.9b0252

“SINTESIS METAL ORGÁNICA DE a- ALUMINA A PARTIR DE ALUMINIO”

El presente estudio describe un proceso de obtención de polvos de a-alúmina que involucra la síntesis de un precursor metalorgánico formiato de aluminio Al(O2CH)3. El formiato de aluminio se sintetiza a partir de aluminio metálico, el cual es disuelto con ácido fórmico, en una reacción que es catalizada por cloruro de mercúrico. La solución resultante se alimenta a un secador por pulverización (spray dryer), proceso utilizado para la eliminación, del solvente y producir una mezcla homogénea de polvos (aglomerados suaves de fácil prensado). Las fuentes de aluminio utilizadas en la síntesis son dos una con pureza del 99.5 % (lámina de Al) y la otra de menor pureza proveniente de latas de aluminio. Se realiza un estudio calorimétrico mediante las técnicas de Análisis Térmico Diferencial, calorimetría diferencial de barrido y Análisis Termo Gravimétrico donde se caracterizan las transformaciones de fase involucradas tanto en la descomposición y en la transición a a- alúmina del formiato de aluminio. Las fases son caracterizadas por difracción de rayos X, espectroscopia infrarroja, Resonancia Magnética Nuclear y microscopia electrónica. La caracterización del formiato de aluminio muestra que posee una estructura octaédrica, donde el aluminio se encuentra enlazado con un anión carboxilato bidentado. Las transformaciones del Al(O2CH)3 se realizan en dos etapas claramente diferenciadas, la primera etapa corresponde a la descomposición del formiato de aluminio, la cual es seguida por la transición a a-alúmina a 11000C a partir de una fase amorfa

“ESTUDIO QUÍMICO ESTRUCTURAL DEL PROCESO DE VITRIFICACIÓN EN CERAMICAS TRIAXIALES”

Este trabajo de investigación consiste en la revisión y estudio del fenómeno de vitrificación de un cuerpo cerámico triaxial (arcilla, cuarzo y feldespato), empleado en la fabricación industrial de cuerpos cerámicos blancos. El estudio químico estructural del proceso de vitrificación, demuestra la utilidad del uso de parámetros químicos estructurales de la matriz vítrea, como parámetros indicadores del proceso de vitrificación y de las propiedades físicas de un cuerpo porcelánico. Mediante técnicas dilatométricas, termo-analíticas, espectroscópicas y de microscopía electrónica, son evidenciadas claramente tres etapas de densificación: la inicial de 250C a 11000C, atribuida a la reducción del área superficial específica de las materias primas, con encogimiento relevante; las transformaciones principales en esta etapa implican: la descomposición de minerales arcillosos, que conducen a la formación de metacaolín amorfo a 4940C, que aproximadamente a 10000C da la formación de dos estructuras cristalinas, una tipo espinela (?-alúmina) y otra de mullita. En esta etapa inicial también ocurre la transformación del feldespato anortoclásico en sanidina a 10000C, a que a la vez da la formación una fase líquida viscosa. La etapa intermedia de 11000C a 12250C, se caracteriza por un mayor encogimiento debido a la fundición progresiva del feldespato y cuarzo, derivando así un incremento de la fase líquida viscosa, la cual es la responsable del reacomodo de las partículas, mediante fuerzas de capilaridad, dando como resultado una mayor densificación. La etapa final de 12250C a 13000C, se caracteriza por una decreciente densificación, contrastada por el efecto del crecimiento de poros alrededor de las partículas de mullita, por el desprendimiento y atrapamiento de gases en la fase líquida. El análisis cinético indica que la energía de activación obtenida es elevada en la etapa intermedia de densificación y su valor se incrementa conforme aumenta la densificación, mostrando así valores de 470 kJ/mol y 497 kJ/mol, para densidades de 2.1 g/cm3 y 2.2 g/cm3. Los valores de energía de activación estimados caen en un rango estipulado para un mecanismo de sinterización vía flujo viscoso. El incremento de energía de activación indica que se requiere de cierta temperatura para que se desarrolle el mecanismo de sinterización vía flujo viscoso, cuya velocidad de densificación depende de la viscosidad de la fase vítrea formada

Antifungal susceptibility of Candida species to copper oxide nanoparticles on polycaprolactone fibers (PCL-CuONPs).

The integration of metallic or ceramic nanoparticles in polymer matrices has improved the antimicrobial and antifungal behavior, resulting in the search for composites with increased bactericidal and antimycotic properties. A polycaprolactone fibers with copper oxide nanoparticles was prepared. Polycaprolactone-copper fibers (PCL- CuONPs) were prepared into two major steps in situ method: (a) Synthesis of CuO particles, then (b) incorporation of polycaprolactone to electrospun process. The first step is the reduction of Cu+2 ions by gallic acid in N,N-dimethylformamide and tetrahydrofuran solution with the simple addition of polycaprolactone in the solution for the second electrospun step. Raman spectra provide information about the nature of the copper oxide synthesized. There are three Raman peaks in the sample, at 294 and 581 cm-1 and a very broad band from 400 to 600 cm-1 which are characteristics bands for CuO. Scanning electron microscopy (TEM) revealed copper oxide nanoparticles with semispherical shapes with diameter 35 ±11 nm. Dynamic light scattering (DLS) analysis showed uniform CuONPs in a range of 88±11 nm. Scanning electron microscopy (SEM) of PCL-CuONps reveled fibers with diameters ranging from 925 to 1080 nm were successfully obtained by electrospinning technique. Orientation, morphology and diameter were influenced by the increment on CuONPs concentration, with the smaller diameter present in samples prepared from low concentrated solutions. The antimycotic applicability of the composite was evaluated to determine the antifungal activity in three species of the genus Candida (Candida albicans, Candida glabrata and Candida tropicalis). PCL-CuONPs exhibit a considerable antifungal effect on all species tested. The preparation of PCL-CuONPs was simple, fast and low-cost for practical application as an antifungal dressing

Antifungal activity and cytotoxicity study of ZrO2-ZnO bimetallic nanoparticles

Antifungal resistance of Candida species is a growing concern worldwide. Therefore, this study presents the synthesis of ZnO and ZrO2-ZnO nanoparticles. Structural features of the nanoparticles are characterized by DLS, SEM, EDX, UV–Visible and Raman spectroscopy. Thereafter, the investigation of the effect of these nanoparticles on Candida species was performed by disk diffusion and broth microdilution method on C. albicans, C. dubliniensis, C. glabrata, and C. tropicalis. The viability activity was also evaluated. Scanning electron micro- scopy showed spherically shaped nanoparticles while dynamic light scattering analysis showed ZrO2 (76 nm), ZnO (22 nm) and ZrO2-ZnO samples between 26 nm and 34 nm respectively. The elemental analysis validated that pure samples were synthesized. The Raman spectra shows ZnO nanoparticles of the wurtzite crystal structure having a group theory that confirms the presence of optic nodes with different properties. Our investigations have shown that mixing ZrO2 with ZnO nanoparticles only show inhibition effect on Candida species at high concentration of ZnO against ZrO2 based on the inhibition zone formed in the disk diffusion and the decrease in the growth characteristics recorded from the broth microdilution analysis. The viability study shows that there is no significance difference in viability as a function of time and concentration on the peripheral human mono- nuclear cells on exposure to the synthesized nanoparticle

Evaluation of Antifungal Activity by Mixed Oxide Metallic Nanocomposite against Candida spp

Abstract: High doses of antimicrobial agents are a huge threat due to the increasing number of pathogenic organisms that are becoming resistant to antimicrobial agents. This resistance has led to a search for alternatives. Therefore, this study presents the synthesis and characterization of ZrO2-Ag2O nanoparticles (NPs) by sol-gel. The NPs were analyzed by dynamic light scattering (DLS), UV-visible (UV-vis), Raman and scanning electron microscopy (SEM). The NPs were later evaluated for their antifungal effects against Candida albicans, Candida dubliniensis, Candida glabrata, and Candida tropicalis, using disc diffusion and microdilution methods, followed by the viability study. The DLS showed sizes for ZrO2 76 nm, Ag2O 50 nm, and ZrO2-Ag2O samples between 14 and 42 nm. UV-vis shows an absorption peak at 300 nm for ZrO2 and a broadband for Ag2O NPs. Raman spectra were consistent with factor group analysis predictions. SEM showed spherically shaped NPs. The antifungal activity result suggested that ZrO2-Ag2O NPs were effective against Candida spp. From the viability study, there was no significance difference in viability as a function of time and concentration on human mononuclear cells. This promising result can contribute toward the development of alternative therapies to treat fungal diseases in humans

Sol–Gel and Electrospinning Synthesis of Silica–Hydroxyapatite–Silver Nanofibers for SEIRAS and SERS

Surface-enhanced Raman spectroscopy (SERS) and Surface-enhanced infrared absorption spectroscopy (SEIRAS) are both novel techniques favored by the excitation of surface plasmons onto metal nanostructures. The light emitted from the metal surface couples with the vibrational transitions of molecules in proximity, enhancing its spectral response and leading to more sensitive and effective spectroscopic analysis. The absence of inexpensive and reproducible substrates is among the major impediments to the accurate implementation and optimal performance of the technique. The development of a low-cost active substrate based on silica–hydroxyapatite through sol–gel synthesis and electrospinning is addressed in the present study. Fibers of 512 ± 199 nm diameter were produced after sintering at 1150 °C on the electrospun mats. The fibers are fixed to an indium tin oxide (ITO) glass base for electrodeposition with 10 and 20 mM AgNO3 at 1.5 and 3.3 V at different time periods. Electrodeposition produced silver nanorods and nanocubes on the fibers. The SERS and SEIRAS activity of each one of the nine supports was tested using pyridine 1 nM, comparing it with the spectrum of pyridine 1 mM. An enhancement factor of 2.01 × 106 for the band at 3335 cm−1 was obtained during a SEIRAS essay for the support doped for 2 min at 3.3 V with 10 mM silver nitrate solution. The highest SERS enhancement factor was 3.46 × 108, for the band at 1567 cm−1 in the substrate doped for 5 min at 1.5 V with silver nitrate solution at 10 mM. After testing both samples with 10−4 M violet crystal solution, no SERS enhancement factor was found, but higher band resolution in the spectra was observed