Impact of volume transition on the net charge of poly-NN-isopropyl acrylamide microgels

We explore the electrostatic properties of poly-N-isopropyl acrylamide microgels in dilute, quasi-de-ionized dispersions and show that the apparent net charge of these thermosensitive microgels is an increasing function of their size, the size being conveniently varied by temperature. Our experimental results obtained in a combination of light scattering, conductivity, and mobility experiments are consistent with those obtained in Poisson-Boltzmann cell model calculations, effectively indicating that upon shrinking the number of counterions entrapped within the microgels increases. Remarkably, this behavior shows that the electrostatic energy per particle remains constant upon swelling or deswelling the microgel, resulting in a square root dependence of the net charge on the particle radius

Interplay between internal structure and optical properties of thermosensitive nanogels

The structural and optical properties of thermosensitive particles, nanogels, are studied by light scattering and refractometry as a function of temperature. Nanogels are composed of poly- N-Isopropopylacrylamide, a polymer that shrinks at temperatures higher than its lower critical solution temperature, 33 °C. The internal nanogel structure obtained by light scattering is well modeled by assuming a constant radial mass density profile convoluted with a Gaussian function. Moreover, we introduce a simple method that allows us to describe the measured temperature-dependent index of refraction of these complex nanoparticles by using their structural information, core dimension and external radius

Estructura de fluidos coloidales binarios

Para probar la validez de la Teoría de Líquidos para mezclas coloidales, se midieron mediante dispersión estática de luz el factor de estructura de una mezcla de microgeles de PNIPAM y el resultado fue comparado con los cálculos teóricos. Para este análisis se generaron dos sistemas monodispersos y posteriormente estos se juntaron para poder crear un sistema binario. Para fijar los parámetros utilizados en los cálculos teóricos, se analizaron por separado cada uno de los sistemas con teoría de líquidos resolviendo las ecuaciones integrales de Ornstein-Zernike con la cerradura HNC (relación de cierre hiperreticulada) y se obtuvieron los valores de concentración de partículas y carga de cada especie. Una vez fijados los parámetros, se aplicó la teoría de líquidos para predecir la estructura de una mezcla que posee una fracción molar de 0.5 y se encontró un buen acuerdo entre la predicción teórica y el experimento.In order to probe the validity of Theory of Liquids for colloidal mixtures, we measured the static structure factor of a binary system composed of two types of PNIPAM microgels and the result was compared with calculations. To achieve that we first characterized separately each microgel system and then they were mixed to obtain the colloidal mixture. The input parameters used in the calculations to predict the structure of the mixture were found previously by analysing the two monodisperse systems by solving the Ornstein-Zernike integral equation with the HNC closure relation (hypernetted closure relation). Once the parameters are known, the theory of liquids was used to predict the structure of a mixture having a molar fraction of 0.5 and the results compared to experiments, finding a good agreement

Estudio de las propiedades estructurales de dispersiones de microgeles de poli(N-isopropilacrilamida) cargadas electrostáticamente en función de la fuerza iónica y la temperatura

En este trabajo se han estudiado las propiedades estructurales de suspensiones coloidales de microgeles de PNIPAM cargados electrostáticamente en función de la fuerza iónica y la temperatura. Los microgeles de PNIPAM fueron sintetizados por medio de polimerización en emulsión con surfactante, considerando una baja concentración de ionizador para que su carga electrostática no sea muy alta y así evitar la cristalización. El sistema analizado posee una concentración de partículas de PNIPAM de 6.9 pp/um³. Los factores de estructura estáticos experimentales, S(q), se obtuvieron mediante dispersión de luz estática con un dispositivo 3D-LS. Los S(q) medidos han sido modelados resolviendo las ecuaciones integrales de Ornstein-Zernike, suponiendo un potencial efectivo repulsivo tipo Yukawa, y usando la cerradura del tipo cadena híper-reticulada (HNC). Los resultados obtenidos muestran como la carga de las partículas decrece al aumentar la temperatura, comportamiento que sólo había sido reportado en sistemas con una baja concentración de partículas y baja fuerza iónica.Here we study the structural properties of charged microgel colloidal suspensions as a function of ionic strength and temperature. The PNIPAM particles have been synthesized by emulsion polymerization using a small initiator concentration to obtain low charged microgels, thus avoiding crystallization. We consider a fixed PNIPAM particle number concentration of 6.9 pp/um³. The static structure factor, S(q), has been measured by static light scattering using a 3D-LS device. The measured S(q)’s have been modeled by solving the Ornstein-Zernike equation, assuming a repulsive Yukawa type effective pair potential and using the Hypernetted-chain approximation (HNC) as a closure relation. The theoretical analysis shows that the particle charge decreases when the temperature increases, finding that only had been reported for systems at low particle concentration and low ionic strength

Evaluación de la eficiencia fotocatalítica de nanopartículas de TiO₂, TiO₂-Au y TiO₂-Ag frente a dos colorantes reactivos

En la actualidad los colorantes son comúnmente utilizados en las industrias farmacéutica y alimenticia, entre otras, siendo la textil responsable de la generación del 20% de las aguas residuales globales. Por lo que en este trabajo se evaluó la eficiencia de nanopartículas de Evaluación de la eficiencia fotocatalítica de nanopartículas de TiO₂, TiO₂-Au y TiO₂-Ag frente a dos colorantes reactivos como agentes fotocatalíticos para la decoloración de aguas contaminadas con colorantes azul reactivo 19 (AR19) y naranja reactivo 84 (NR84) a 20, 50 y 100 ppm utilizando lámparas led de 375 nm. Para el AR19 a 100 ppm en 2 horas se obtuvieron decoloraciones de 27.62, 17.31 y 13.37%, para Evaluación de la eficiencia fotocatalítica de nanopartículas de TiO₂, TiO₂-Au y TiO₂-Ag frente a dos colorantes reactivos respectivamente, siguiendo el mismo orden para el NR84 las decoloraciones corresponden al 97.61, 84.55 y 32.28%, por lo que se comprueba la eficiencia en la decoloración, al disminuir la concentración los tiempos de remoción se reducen.Nowadays dyes are commonly used in the pharmaceutical, food and textile industries being textile responsible for the generation of 20% of global wastewater. Therefore, in this work the efficiency of TiO₂, TiO₂-Au and TiO₂-Ag nanoparticles was evaluated as photocatalytic agents for the discoloration of contaminated water with dyes reactive blue 19 (AR19) and reactive orange 84 (NR84) at 20, 50 and 100 ppm using 375 nm led lamps. For AR19 at 100 ppm in 2 hours, discolorations of 27.62, 17.31 and 13.37% were obtained, for TiO₂, TiO₂-Au and TiO₂-Ag respectively, following the same order for NR84 the discolorations correspond to 97.61, 84.55 and 32.28%, so that the efficiency in the discoloration is confirmed, reducing the concentration the final removal times are also reduced

Evaluación del efecto de inhibición bacteriana de micropartículas core@shell en agua natural

La problemática de las enfermedades biológico-infecciosas causadas por el consumo de aguas contaminadas se encuentra en un estado alarmante, por lo que día a día se buscan nuevas técnicas para la erradicación de bacterias patógenas presentes en agua, una gran alternativa para la eliminación de dichos contaminantes es el uso de micromateriales metálicos de fácil recuperación. Por lo que, en este trabajo se presenta una metodología para obtener micropartículas de magnetita cubiertas con plata (core@shell) mediante síntesis verde, con la finalidad de evaluar su efecto inhibitorio sobre de Bacillus subtilis y Escherichia coli en presencia de dichas micropartículas. Los experimentos fueron evaluados en un lapso de 24 horas, donde se encontró que las core@shell inhiben en su totalidad el desarrollo bacteriano, demostrando tener un efecto bactericida. Debido al centro paramagnético de las core@shell su recuperación se lleva a cabo mediante un imán de forma rápida y eficiente.The problem of biological-infectious diseases caused by the consumption of contaminated water is in an alarming state, every day new techniques are sought for the eradication of pathogenic bacteria present in water, a great alternative for the elimination of these contaminants is the use of metallic micromaterials. This paper presents a methodology to obtain magnetite microparticles covered with silver (core@shell) by green synthesis, in order to evaluate the effect of inhibition of bacterial growth of Bacillus subtilis and Escherichia coli in the presence of the microparticles. The experiments were evaluated in a 24-hour period, where was found that core@shell completely inhibit bacterial development, proving to have a bactericidal effect. Due to the paramagnetic center of the core@shell, its recovery is carried out by means of a magnet, quickly and efficiently

Accounting for effective interactions among charged microgels

We introduce a theoretical approach to describe structural correlations among charged permeable spheres at finite particle concentrations. This theory explicitly accounts for correlations among microions and between microions and macroions and allows for the proposal of an effective interaction among macroions that successfully captures structural correlations observed in poly- N -isopropyl acrylamide microgel systems. In our description the bare charge is fixed and independent of the microgel size, the microgel concentration, and the ionic strength, which contrasts with results obtained using linear response approximations, where the bare charge needs to be adapted to properly account for microgel correlations obtained at different conditions

Síntesis, caracterización y funcionalización de nanopartículas de oro para su uso en biosensores

Actualmente los nanomateriales juegan un papel importante en el desarrollo de nuevas tecnologías basadas en sensores y biosensores, debido a su gran sensibilidad, fácil manejo y bajo costo, ya que se manejan volúmenes nanométricos. Es por esto que en este trabajo se desarrolló un procedimiento simple y rápido para la síntesis de nanopartículas de oro basado en la metodología propuesta por de la Escosura-Muñiz y colaboradores, las cuales fueron caracterizadas mediante las técnicas de espectrofotometría de UV-visible y dispersión de luz dinámica. Posteriormente se optimizaron las condiciones de incubación necesarias como temperatura, tiempo y velocidad de incubación para la funcionalización superficial de las nanopartículas de oro con un anticuerpo específico para Salmonella typhi.Nanomaterials currently play an important role in the development of new technologies based on sensors and biosensors, due to its high sensitivity, easy handling and low cost since nanometric volumes are handled. In this paper a simple and rapid procedure for the synthesis of gold nanoparticles based on the methodology proposed by de la Escosura-Muñiz et al. was developed, these nanoparticles were characterized by techniques UV-visible spectrophotometry and dynamic light scattering. After this, the incubation conditions for surface functionalization of gold nanoparticles with a specific antibody for Salmonella typhi were optimized, as well as parameters such as temperature, incubation time and speed

The state of health in the European Union (EU-27) in 2019: a systematic analysis for the Global Burden of Disease study 2019

Background: The European Union (EU) faces many health-related challenges. Burden of diseases information and the resulting trends over time are essential for health planning. This paper reports estimates of disease burden in the EU and individual 27 EU countries in 2019, and compares them with those in 2010.Methods: We used the Global Burden of Disease 2019 study estimates and 95% uncertainty intervals for the whole EU and each country to evaluate age-standardised death, years of life lost (YLLs), years lived with disability (YLDs) and disability-adjusted life years (DALYs) rates for Level 2 causes, as well as life expectancy and healthy life expectancy (HALE).Results:In 2019, the age-standardised death and DALY rates in the EU were 465.8 deaths and 20,251.0 DALYs per 100,000 inhabitants, respectively. Between 2010 and 2019, there were significant decreases in age-standardised death and YLL rates across EU countries. However, YLD rates remained mainly unchanged. The largest decreases in age-standardised DALY rates were observed for "HIV/AIDS and sexually transmitted diseases" and "transport injuries" (each -19%). "Diabetes and kidney diseases" showed a significant increase for age-standardised DALY rates across the EU (3.5%). In addition, "mental disorders" showed an increasing age-standardised YLL rate (14.5%).Conclusions: There was a clear trend towards improvement in the overall health status of the EU but with differences between countries. EU health policymakers need to address the burden of diseases, paying specific attention to causes such as mental disorders. There are many opportunities for mutual learning among otherwise similar countries with different patterns of disease

Global, regional, and national cancer incidence, mortality, years of life lost, years lived with disability, and disability-Adjusted life-years for 29 cancer groups, 1990 to 2017 : A systematic analysis for the global burden of disease study

Importance: Cancer and other noncommunicable diseases (NCDs) are now widely recognized as a threat to global development. The latest United Nations high-level meeting on NCDs reaffirmed this observation and also highlighted the slow progress in meeting the 2011 Political Declaration on the Prevention and Control of Noncommunicable Diseases and the third Sustainable Development Goal. Lack of situational analyses, priority setting, and budgeting have been identified as major obstacles in achieving these goals. All of these have in common that they require information on the local cancer epidemiology. The Global Burden of Disease (GBD) study is uniquely poised to provide these crucial data. Objective: To describe cancer burden for 29 cancer groups in 195 countries from 1990 through 2017 to provide data needed for cancer control planning. Evidence Review: We used the GBD study estimation methods to describe cancer incidence, mortality, years lived with disability, years of life lost, and disability-Adjusted life-years (DALYs). Results are presented at the national level as well as by Socio-demographic Index (SDI), a composite indicator of income, educational attainment, and total fertility rate. We also analyzed the influence of the epidemiological vs the demographic transition on cancer incidence. Findings: In 2017, there were 24.5 million incident cancer cases worldwide (16.8 million without nonmelanoma skin cancer [NMSC]) and 9.6 million cancer deaths. The majority of cancer DALYs came from years of life lost (97%), and only 3% came from years lived with disability. The odds of developing cancer were the lowest in the low SDI quintile (1 in 7) and the highest in the high SDI quintile (1 in 2) for both sexes. In 2017, the most common incident cancers in men were NMSC (4.3 million incident cases); tracheal, bronchus, and lung (TBL) cancer (1.5 million incident cases); and prostate cancer (1.3 million incident cases). The most common causes of cancer deaths and DALYs for men were TBL cancer (1.3 million deaths and 28.4 million DALYs), liver cancer (572000 deaths and 15.2 million DALYs), and stomach cancer (542000 deaths and 12.2 million DALYs). For women in 2017, the most common incident cancers were NMSC (3.3 million incident cases), breast cancer (1.9 million incident cases), and colorectal cancer (819000 incident cases). The leading causes of cancer deaths and DALYs for women were breast cancer (601000 deaths and 17.4 million DALYs), TBL cancer (596000 deaths and 12.6 million DALYs), and colorectal cancer (414000 deaths and 8.3 million DALYs). Conclusions and Relevance: The national epidemiological profiles of cancer burden in the GBD study show large heterogeneities, which are a reflection of different exposures to risk factors, economic settings, lifestyles, and access to care and screening. The GBD study can be used by policy makers and other stakeholders to develop and improve national and local cancer control in order to achieve the global targets and improve equity in cancer care. © 2019 American Medical Association. All rights reserved.Peer reviewe