Fotoelectroquímica y espectroelectroquímica de materiales semiconductores nanoestructurados

Tesis (Dra. en Ciencias Químicas) - - Universidad Nacional de Córdoba. Facultad de Ciencias Químicas, 2019Los semiconductores nanoestructurados presentan propiedades que dependen de las dimensiones del material. En la actualidad estos materiales se estudian intensivamente debido a su potencial aplicación en dispositivos fotovoltaicos. La optimizáción de su preparación permite controlar propiedades ópticas y electrónicas que pueden ser útiles en su aplicación en celdas solares mejorando la eficiencia de conversión energética. En este trabajo de tesis, se busca optimizar la síntesis de semiconductores nanoestructurados y optimizar la preparación de materiales híbridos derivados de los anteriores con el objetivo principal de mejorar la eficiencia de conversión de celdas solares sensibilizadas con puntos cuánticos. En el capítulo 1 de la introducción de esta tesis se comenta el rol de los materiales semiconductores nanoestructurados que presentan aplicación en dispositivos fotovoltaicos en la actualidad, en un contexto mundial de necesidad de ampliar el aporte de energía solar en la matriz energética. Se discuten aspectos teóricos relativos a las propiedades ópticas y electrónicas de materiales semiconductores y cómo se explotan estas propiedades en el desarrollo de celdas solares de tercera generación. El capítulo 2 de la introducción se encuentra abocado a una descripción y discusión sobre aspectos teóricos y experimentales de las técnicas de caracterización espectroelectroquímicas y fotoelectroquímicas utilizadas en este trabajo de tesis. En la parte de resultados se muestran los procedimientos de síntesis y estudio de distintos materiales semiconductores nanoestructurados. En primer lugar se describen en los capítulos 3 y 4 la síntesis y preparación de óxidos semiconductores base. En el capítulo 3 se muestra la optimización de la preparación de nanovarillas de ZnO. Se exponen los resultados de la caracterización de propiedades fotoelectroquímicas y espectroelectroquímicas dependientes de las dimensiones de las nanovarillas preparadas. En el capítulo 4 se muestran los resultados de la preparación de membranas de nano tubos de Ti02 y distintas aplicaciones estudiadas de este sistema. En el capítulo 7 se muestran los resultados de la sensibilización óptica de nanotubos de Ti02 con distintos nanocristales de CdSe. Por último en el capítulo 8 se muestra la caracterización espectroelectroquímia de nanocristales de calcogenuros de cobre que presentan propiedades ópticas de resonancia de plasmón superficial localizada. En las conclusiones de la tesis se resumen los logros más importantes alcanzados para cada sistema estudiado, y se realiza un breve comentario respecto a los principales desafíos que deben resolverse en el futuro para la aplicación de materiales semiconductores nanoestructurados2020-12-31Fil: Benavente Llorente, Victoria. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas; Argentina.Fil: Iglesias, Rodrigo Alejandro. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Departamento de Fisicoquímica; Argentina.Fil: Iglesias, Rodrigo Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones en Físico Química de Córdoba; Argentina.Fil: Sánchez, Cristian Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto Interdisciplinario de Ciencias Básicas; Argentina.Fil: Pacioni, Natalia Lorena. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Departamento de Química Orgánica; Argentina.Fil: Pacioni, Natalia Lorena. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones en Fisicoquímica de Córdoba; Argentina.Fil: Cámara, Osvaldo Raúl. Universidad Nacional de Córdoba. Facultad de Ciencias Químicas. Departamento de Fisicoquímica; Argentina.Fil: Cámara, Osvaldo Raúl. Consejo Nacional de Investigaciones Científicas y Técnicas. Instituto de Investigaciones en Fisicoquímica de Córdoba; Argentina.Fil: Gassa, Liliana Mabel. Universidad Nacional de La Plata. Facultad de Ingeniería. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina

RELACIÓN ENTRE LA VÍA DE ADMINISTRACIÓN DEL SULFATO FERROSO Y LA EXPERIENCIA DE CARIES DENTAL EN NIÑOS DE 1 A 3 AÑOS. PUESTO DE SALUD SAN JOSÉ – CAYMA. AREQUIPA, 2014

SULFATO FERROSO FARMACOCINÉTICA DEL HIERRO SUPLEMENTACIÓN PREVENTIVA CON HIERRO ADMINISTRACIÓN DE SULFATO FERROSO VÍA ORAL ADMINISTRACIÓN DE SULFATO FERROSO VÍA PLACENTARIA EFECTOS ADVERSOS DEL SULFATO FERROSO EFECTOS DEL SULFATO FERROSO SOBRE LAS PIEZAS DENTALES CARIES DENTAL COMPONENTES DE LA CARIES DENTAL FACTORES PREDISPONENTES DE LA CARIES DENTAL EVALUACIÓN DE RIESGO DE CARIES DENTAL ÍNDICE DE CARIES DENTAL ALTERACIONES DE LA ESTRUCTURA DEL DIENT

A high performance system to study the influence of temperature in on-line solid-phase extraction capillary electrophoresis

A novel high performance system to control the temperature of the microcartridge in on-line solid phase extraction capillary electrophoresis (SPE–CE) is introduced. The mini-device consists in a thermostatic bath that fits inside of the cassette of any commercial CE instrument, while its temperature is controlled from an external circuit of liquid connecting three differentwater baths. The circuits are controlled from a switchboard connected to an array of electrovalves that allow to rapidly alternate the water circulation through the mini-thermostatic-bath between temperatures from 5 to 90 ºC. The combination of the mini-device and the forced-air thermostatization system of the commercial CE instrument allows to optimize independently the temperature of the sample loading, the clean-up, the analyte elution and the electrophoretic separation steps. The system is used to study the effect of temperature on the C18-SPE–CE analysis of the opioid peptides, Dynorphin A (Dyn A), Endomorphin1 (END) and Met-enkephalin (MET), in both standard solutions and in spiked plasma samples. Extraction recoveries demonstrated to depend, with a non-monotonous trend, on the microcartridge temperature during the sample loading and became maximum at 60 ºC. Results prove the potential of temperature control to further enhance sensitivity in SPE–CE when analytes are thermally stable.Facultad de Ciencias ExactasLaboratorio de Investigación y Desarrollo de Métodos Analíticos (LIDMA)Centro de Investigación y Desarrollo en Tecnología de Pintura

Evaluation of on-line solid-phase extraction capillary electrophoresis-mass spectrometry with a nanoliter valve for the analysis of peptide biomarkers

On-line solid-phase extraction capillary electrophoresis-mass spectrometry (SPE-CE-MS) is a powerful technique for high throughput sample clean-up and analyte preconcentration, separation, detection, and characterization. The most typical design due to its simplicity and low cost is unidirectional SPE-CE-MS. However, in this configuration, the sample volumes introduced by pressure depend on the dimensions of the separation capillary and some matrix components could be irreversibly adsorbed in its inner walls. Furthermore, in many cases, the requirements of on-line preconcentration are incompatible with the background electrolyte necessary for an efficient separation and sensitive MS detection. Here, we present SPE-CE-MS with a nanoliter valve (nvSPE-CE-MS) to overcome these drawbacks while keeping the design simple. The nvSPE-CE-MS system is operated with a single CE instrument and two capillaries for independent and orthogonal SPE preconcentration and CE separation, which are interfaced through an external and electrically isolated valve with a 20 nL sample loop. The instrumental setup is proved for the analysis of opioid and amyloid beta peptide biomarkers in standards and plasma samples. NvSPE-CE-MS allowed decreasing the limits of detection (LODs) 200 times with regard to CE-MS. Compared to unidirectional SPE-CE-MS, peak efficiencies were better and repeatabilities similar, but total analysis times longer and LODs for standards slightly higher due to the heart-cut operation and the limited volume of the valve loop. This small difference on the LODs for standards was compensated for plasma samples by the improved tolerance of nvSPE-CE-MS to complex sample matrices. In view of these results, the presented setup can be regarded as a promising versatile alternative to avoid complicated matrix samples entering the separation capillary in SPE-CE-MS

Sensitive analysis of recombinant human erythropoietin glycopeptides by on-line phenylboronic acid solid-phase extraction capillary electrophoresis-mass spectrometry

In this study, several chromatographic sorbents: porous graphitic carbon (PGC), aminopropyl hydrophilic interaction (aminopropyl-HILIC), and phenylboronic acid (PBA) were assessed for the analysis of glycopeptides by on-line solid-phase extraction capillary electrophoresis mass spectrometry (SPE-CEMS). As the PBA sorbent provided the most promising results, a PBA-SPE-CE-MS method was developed for the selective and sensitive preconcentration of glycopeptides from enzymatic digests of glycoproteins. Recombinant human erythropoietin (rhEPO) was selected as the model glycoprotein and subjected to enzymatic digestion with several proteases. The tryptic O126 and N83 glycopeptides from rhEPO were targeted to optimize the methodology. Under the optimized conditions, intraday precision, linearity, limits of detection (LODs), and microcartridge lifetime were evaluated, obtaining improved results compared to that from a previously reported TiO2-SPE-CE-MS method, especially for LODs of N-glycopeptides (up to 500 times lower than by CE-MS and up to 200 times lower than by TiO2-SPE-CE-MS). Moreover, rhEPO Glu-C digests were also analyzed by PBA-SPE-CE-MS to better characterize N24 and N38 glycopeptides. Finally, the established method was used to analyze two rhEPO products (EPOCIM and NeuroEPO plus), demonstrating its applicability in biopharmaceutical analysis. The sensitivity of the proposed PBA-SPE-CEMS method improves the existing CE-MS methodologies for glycopeptide analysis and shows a great potential in glycoprotein analysis to deeply characterize protein glycosites even at low concentrations of the protein digest

Protein profiling and classification of commercial quinoa grains by MALDI-TOF-MS and chemometrics

Quinoa is an Andean grain that is attracting attention worldwide as a high-quality protein-rich food. Nowadays, quinoa foodstuffs are susceptible to adulteration with cheaper cereals. Therefore, there is a need to develop novel methodologies for protein characterization of quinoa. Here, we first developed a matrix-assisted laser desorption ionization time-of-flight mass spectrometry (MALDI-TOF-MS) method to obtain characteristic mass spectra of protein extracts from 4 different commercial quinoa grains, which group different varieties marketed as black, red, white (from Peru) and royal (white from Bolivia). Then, data preprocessing and peak detection with MALDIquant allowed detecting 47 proteins (being 30 tentatively identified), the intensities of which were considered as fingerprints for multivariate data analysis. Finally, classification by partial least squares discriminant analysis (PLS-DA) was excellent, and 34 out of the 47 proteins were critical for differentiation, confirming the potential of the methodology to obtain a reliable classification of quinoa grains based on protein fingerprinting

Analysis of circulating microRNAs and their post-transcriptional modifications in cancer serum by on-line solid-phase extraction-capillary electrophoresis-mass spectrometry

In this paper, an on-line solid-phase extraction capillary electrophoresis-mass spectrometry (SPE-CE-MS) method is described for the purification, preconcentration, separation, and characterization of endogenous microRNA (miRNA) and their post-transcriptional modifications in serum. First, analysis by CE-MS was optimized using a standard mixture of hsa-miR-21-5p (miR-21-5p) and hsa-let-7g-5p (let-7g-5p). For SPE-CE-MS, a commercial silicon carbide (SiC) resin was used to prepare the microcartridges. Under the optimized conditions with standards, the microcartridge lifetime (>25 analyses) and repeatability (2.8% RSD for the migration times; 4.4 and 6.4% RSD for the miR-21-5p and let-7g-5p peak areas, respectively) were good, the method was linear between 25 and 100 nmol·L-1, and the limit of detection (LOD) was around 10 nmol·L-1 (50 times lower than by CE-MS). In order to analyze human serum samples, an off-line sample pretreatment based on phenol/chloroform/isoamyl alcohol (PCA) extraction was necessary prior to SPE-CE-MS. The potential of the SPE-CE-MS method to screen for B-cell chronic lymphocytic leukemia (CLL) was demonstrated by an analysis of serum samples from healthy controls and patients. MicroRNAs, specifically miR-21-5p and a 23 nucleotide long 5'-phosphorylated miRNA with 3'-uridylation (iso-miR-16-5p), were only detected in the CLL patients

Determination of acidity constants and prediction of electrophoretic separation of amyloid beta peptides

In this paper we describe a strategy to estimate by CE the acidity constants (pKa) of complex polyprotic peptides from their building peptide fragments. CE has been used for the determination of the pKas of five short polyprotic peptides that cover all the sequence of amyloid beta (Aβ) peptides 1-40 and 1-42 (Aβ fragments 1-15, 10-20, 20-29, 25-35 and 33-42). First, the electrophoretic mobility (me) was measured as a function of pH of the background electrolyte (BGE) in the pH range 2-12 (bare fused silica capillary, I=25mM and T=25ºC). Second, the mes were fitted to equations modelling the ionisable behaviour of the different fragments as a function of pH to determine their pKas. The accuracy of the pKas was demonstrated predicting the electrophoretic behaviour of the studied fragments using the classical semiempirical relationships between me and peptide charge-to-mass ratio (me vs. q/Mr1/2, classical polymer model, q=charge and Mr=relative molecular mass). Separation selectivity in a mixture of the fragments as a function of pH was evaluated, taking into account the influence of the EOF at each pH value, and a method for the simple and rapid simulation of the electropherograms at the optimum separation pH was described. Finally, the pKas of the fragments were used to estimate the pKas of the Aβ peptides 1-40 and 1-42 (tC and D 3.1, E 4.6 and Y 10.8 for acidic amino acids and tN-D 8.6, H 6.0, K 10.6 and R 12.5 for basic amino acids), which were used to predict their behaviour and simulate their electropherograms with excellent results. However, as expected due to the very small differences on q/Mr1/2 values, separation resolution of their mixtures was poor over the whole pH range. The use of poly(vinyl alcohol) (PVA) coated capillaries allowed reducing the electroosmotic flow (EOF) and a slight improvement of resolution

A Proteomics Data Mining Strategy for the Identification of Quinoa Grain Proteins with Potential Immunonutritional Bioactivities

Quinoa proteins are attracting global interest for their wide amino acid profile and as a promising source for the development of biomedical treatments, including those against immunemediated diseases. However, information about the bioactivity of quinoa proteins is scarce. In this study, a quinoa grain proteome map obtained by label-free mass spectrometry-based shotgun proteomics was investigated for the identification of quinoa grain proteins with potential immunonutritional bioactivities, including those related to cancer. After carefully examining the sequence similarities of the 1211 identified quinoa grain proteins against already described bioactive proteins from other plant organisms, 71, 48, and 3 of them were classified as antimicrobial peptides (AMPs), oxidative stress induced peptides (OSIPs), and serine-type protease inhibitors (STPIs), respectively, suggesting their potential as immunomodulatory, anti-inflammatory, and anticancer agents. In addition, data interpretation using Venn diagrams, heat maps, and scatterplots revealed proteome similarities and differences with respect to the AMPs, OSIPs, and STPIs, and the most relevant bioactive proteins in the predominant commercial quinoa grains (i.e., black, red, white (from Peru), and royal (white from Bolivia)). The presented proteomics data mining strategy allows easy screening for potentially relevant quinoa grain proteins and commercial classes for immunonutrition, as a basis for future bioactivity testing

Characterization of glycoproteins by capillary electrophoresis electrospray mass spectrometry (CE-ESI-MS). Applications to diagnosis in biomedicine

Glycosylation is the most common posttranslational modification in proteins and the carbohydrates participate in many biological processes. The number and type of glycoforms for a certain glycoprotein may change as a consequence of pathological processes. In our work a method for the separation of transferrin sialoforms has been developed, that permits the diagnostic of Congenital Disorders of Glycosylation (CDG) using a polybrene-dextran sulphate coating and CE-ESI-TOF methodologies. In order to improve the sensitivity the use of solid-phase extraction coupled on-line to CE-ESI-MS is studied and the SPE-CE-ESI-MS developed methods are applied for the characterization of rHuEPO glycoforms. The achieved separation and the high mass-resolving power of flight (TOF) mass detection allows to establish the most probable rHuEPO glycoforms