ABSTRACT
Resumen Se analizaron los cambios entálpicos y entrópicos derivados del proceso de adsorción de acetaminofén sobre carbones activados con química superficial modificada. Se realizó, además, una variación del pH para determinar los cambios en las propiedades termodinámicas cuando existen cargas en el adsorbato y en el adsorbente. Se encontró que la máxima capacidad de adsorción (1,172 mmoles g-1) corresponde al proceso llevado a cabo en el carbón activado denominado CAR en este estudio a pH 7; los valores de las funciones termodinámicas de entalpía de inmersión y entropía de adsorción fueron -36,02 J g-1 y 0,123 J g-1 K-1, respectivamente. Así, el cambio de entropía de adsorción para el acetaminofén en los carbones activados estudiados dependió del pH. Se encontró que esta función termodinámica varía en el siguiente orden pH 2 > pH 11 > pH 7. Este comportamiento se relaciona con el número de especies presentes en la solución capaces de interactuar con la superficie del carbón activado.
Abstract The enthalpic and entropic changes resulting from the process of acetaminophen adsorption on activated carbons with modified surface chemistry were studied. A pH variation was performed to determine the changes in the thermodynamic properties when there are charges in the adsorbate and adsorbent. It was found that the maximum adsorption capacity (1.172 mmoles g-1) corresponds to the process carried out in the activated charcoal labeled as CAR in this study at pH 7; the values of the thermodynamic functions immersion enthalpy and entropy of adsorption were -36.02 J g-1 and 0.123 J g-1 K-1, respectively. Thus, the adsorption entropy change for the acetaminophen on the activated carbons depended on the pH. It was found that this thermodynamic function varies in the following order pH 2 > pH 11 > pH 7. This behavior is related to the number of species present in the solution capable of interact with the activated carbon surface.
Resumo Foram analisadas as mudanças entrópicas e entalpicas resultantes do processo de adsorção de acetaminofeno sobre carvões activados com superfície química modificada. Além disso, foi realizada uma variação do pH para determinar as alterações nas propriedades termodinâmicas quando existem cargas no adsorbato e no adsorvente. Foi encontrado que a máxima capacidade de adsorção (1.172 mmol g-1) corresponde ao processo realizado no carvão ativado chamado CAR neste estudo em pH 7; os valores das funções termodinâmicas de entalpia de imersão e entropia de adsorção foram -36,02 J g-1 e 0,123 J g-1 K-1 respectivamente. As mudança da entropia de adsorção para o acetaminofeno nos carvões activados dependeu do pH. Foi encontrado que esta função termodinâmica varia na seguinte ordem pH 2 > pH 11 > pH 7. Este comportamento está relacionado ao número de espécies presentes na solução capaz de interagir com a superfície de carvão activado.
ABSTRACT
Biofilms are commonly associated with an increased risk of catheter-associated infection. To study the efficacy of materials designed to reduce biofilm formation, microbial biofilms on clinically used urinary catheter were examined. We performed 2, 3-bis (2-methyoxy-4-nitro-5-sulfo-phenyl)-2H-tetrazolium-5-carboxanilide (XTT) reduction assay to determine of biofilm formation ability and observed with scanning electron microscopy (SEM) to analyze biofilm architecture. Additionally, we calculated relative cell surface hydrophobicity (CSH) to measure hydrophobicity of microorganisms. On SEM, catheter surfaces made of latex or anti-infective (IC)-latex were rough but those of silicone, hydrogel-coated silicone (HCS), or silver-alloy-coated silicone (SCS) were relatively smoother. According to XTT reduction assay, biofilm formation was reduced on the surface of smooth silicone-based catheters compared to rough latex-based catheters. The greatest to lowest formation of microbial biofilm were as follows for these material types: silicone-elastomer-coated (SEC) latex > latex > silicone > IC-latex > HCS > SCS. Catheter materials can affect the microbial biofilm formations. First, rougher surfaces on the catheter made the microbial attachment easier and a greater amount of biofilm was formed. Second, when chemicals that inhibit growth and attachment of microorganisms on the inner and outer surfaces of the catheters were applied, the biofilm formation was inhibited. SCS was found to be the most effective in reducing the microbial biofilm formation. These results indicate that microbial biofilm formation may be closely related to the surface roughness and microbial CSH.
Subject(s)
Biofilms , Catheter-Related Infections , Catheters , Hydrophobic and Hydrophilic Interactions , Latex , Microscopy, Electron, Scanning , Silicon , Silicones , Urinary CathetersABSTRACT
Free energy simulations using the Metropolis Monte Carlo method and the coupling parameter approach with umbrella sampling are described for several problems of interest in structural biochemistry; the liquid water, the hydrophobic interaction of alkyl and phenyl groups in water and solvent effects on the conformational stability of the alanine dipeptide and the dimethyl phosphate anion in water. Proximity analysis of results is employed to identify stabilizing factors. Implications of result with respect to the structural chemistry of proteins and nucleic acids is considered.