Formation of Alginate/Chitosan Interpenetrated Networks Revealed by EPR Spectroscopy.

This study analyzes the physico-chemical properties of interpenetrated polymer networks (IPNs) and semi-IPN resulting from cross-linking chitosan with glutaraldehyde and alginate with Ca2+ cations, as a function of the order in which the cross-linking agents are added to the polymer mixture. Three physico-chemical methods were used to assess the differences between systems: rheology, IR spectroscopy, and electron paramagnetic resonance (EPR) spectroscopy. While rheology and IR spectroscopy are commonly used to characterize gel materials, EPR spectroscopy is rarely used, but has the advantage of providing local information about the dynamics of a system. The rheological parameters, which describe the global behavior of the samples, show that semi-IPN systems have a weaker gel behavior and the order of introducing the cross-linker in the polymer systems plays a role. The IR spectra of samples resulting by adding only Ca2+ or Ca2+ as the first cross-linker are similar to that of the alginate gel, while the spectra of samples in which glutaraldehyde is firstly added resemble the chitosan gel spectrum. Using spin-labeled alginate and spin-labeled chitosan, we monitored the changes occurring in the dynamic of the spin labels due to the formation of IPN and semi-IPN. The results show that the order of adding the cross-linking agents influences the dynamic of the IPN network, and that the formation of the alginate network determines the characteristics of the entire IPN system. The EPR data were correlated with the rheological parameters and IR spectra of the analyzed samples.

Evaluation of the Accessibility of Molecules in Hydrogels Using a Scale of Spin Probes.

In this work, we explored by means of electron paramagnetic resonance (EPR) spectroscopy the accessibility of a series of spin probes, covering a scale of molecular weights in the range of 200-60,000 Da, in a variety of hydrogels: covalent network, ionotropic, interpenetrating polymer network (IPN) and semi-IPN. The covalent gel network consists of polyethylene or polypropylene chains linked via isocyanate groups with cyclodextrin, and the ionotropic gel is generated by alginate in the presence of Ca2+ ions, whereas semi-IPN and IPN gel networks are generated in a solution of alginate and chitosan by adding crosslinking agents, Ca2+ for alginate and glutaraldehyde for chitosan. It was observed that the size of the diffusing species determines the ability of the gel to uptake them. Low molecular weight compounds can diffuse into the gel, but when the size of the probes increases, the gel cannot uptake them. Spin-labelled Pluronic F127 cannot be encapsulated by any covalent gel, whereas spin-labelled albumin can diffuse in alginate gels and in most of the IPN networks. The EPR spectra also evidenced the specific interactions of spin probes inside hydrogels. The results suggest that EPR spectroscopy can be an alternate method to evaluate the mesh size of gel systems and to provide information on local interactions inside gels.

Chemical Degradation of Methylene Blue Dye Using TiO2/Au Nanoparticles.

Gold nanoparticles (~10 nm) were deposited on titanium dioxide nanoparticles (~21 nm) and the material obtained was characterized using IR, UV-Vis, N2 adsorption-desorption isotherm, DLS, EDS (EDX), TEM, XPS, and XRD techniques. It was found that the methylene blue dye is degraded in the presence of this material when using hydrogen peroxide as the oxidant. Tests were performed at 2, 4, 6, and 24 h, with hydrogen peroxide contents varying from 1 to 5 mg/mL. Longer exposure time and a higher content of oxidant led to the degradation of methylene blue dye at up to 90%. The material can be reused several times with no loss of activity.

Model Systems for Evidencing the Mediator Role of Riboflavin in the UVA Cross-Linking Treatment of Keratoconus.

Riboflavin under UVA radiation generates reactive oxygen species (ROS) that can induce various changes in biological systems. Under controlled conditions, these processes can be used in some treatments for ocular or dermal diseases. For instance, corneal cross-linking (CXL) treatment of keratoconus involves UVA irradiation combined with riboflavin aiming to induce the formation of new collagen fibrils in cornea. To reduce the damaging effect of ROS formed in the presence of riboflavin and UVA, the CXL treatment is performed with the addition of polysaccharides (dextran). Hyaluronic acid is a polysaccharide that can be found in the aqueous layer of the tear film. In many cases, keratoconus patients also present dry eye syndrome that can be reduced by the application of topical solutions containing hyaluronic acid. This study presents physico-chemical evidence on the effect of riboflavin on collagen fibril formation revealed by the following methods: differential scanning microcalorimetry, rheology, and STEM images. The collagen used was extracted from calf skin that contains type I collagen similar to that found in the eye. Spin trapping experiments on collagen/hyaluronic acid/riboflavin solutions evidenced the formation of ROS species by electron paramagnetic resonance measurements.

Conformational preferences of TEMPO type radicals in complexes with cyclodextrins revealed by a combination of EPR spectroscopy, induced circular dichroism and molecular modeling.

Electron paramagnetic resonance (EPR) spectroscopy is the main tool for evidencing the formation of inclusion complexes of cyclodextrins with paramagnetic guests, based on changes in the EPR parameters. In-depth information on complexation can only be obtained by a combination of physico-chemical methods. Herein we report on the interaction of three TEMPO (2,2,6,6-tetramethylpiperidine 1-oxyl) type radicals with cyclodextrins by collecting and analysing data provided experimentally by EPR and circular dichroism spectroscopies and theoretically by density functional theory and molecular docking. The study focused on the pH influence on the complexation of three paramagnetic probes with cyclodextrins. The EPR spectra revealed that the type and protonation state of the substituent linked to the TEMPO structure influences the affinity of the paramagnetic group for the cyclodextrin cavity. Neutral radical species favour stronger association with cyclodextrins and inclusion of the nitroxide group into the cavity, especially in the case of 4-carboxy-TEMPO. Induced circular dichroism signals of neutral species varied in sign and intensity as a function of substituent and cyclodextrin type. Density functional theory and molecular docking results supported the experimental data regarding the conformational preferences of TEMPO radicals in complexes with cyclodextrins.

Synthesis of Fluorescent Dansyl Derivatives of Methoxyamine and Diphenylhydrazine as Free Radical Precursors.

Starting from dansyl-chloride, in reaction with 1,1-diphenylhydrazine and methoxyamine, two new fluorescent derivatives 1 and 2 were obtained and characterized by NMR, IR, UV-Vis, HR-MS, and fluorescence spectroscopy. The single-crystal X-ray structure was obtained for compound 2. Both compounds generate free radicals by oxidation, as demonstrated by ESR spectroscopy. Compound 1 generates the corresponding hydrazyl-persistent free radical, evidenced directly by ESR spectroscopy, while compound 2 generates in the first instance the methoxyaminyl short-lived free radical, which decomposes rapidly with the formation of the methoxy radical, evidenced by the ESR spin-trapping technique. By oxidation of compounds 1 and 2, their fluorescence is quenched.

Solvatochromic characteristics of dansyl molecular probes bearing alkyl diamine chains.

A series of dansyl-based fluorescent probes bearing linear alkyl-1,n-diamine chains of different length (DA1.n, n = 2-8, 10, 12) was characterized in terms of the absorptive and emissive features in solvents of different polarity and hydrogen bond donor/hydrogen bond acceptor character. The probes show solvent-dependent absorption, a feature that is uncommon among dansyl derivatives. The dual emission of DA1.n probes is strong in non-aqueous solvents and is influenced by the chain length and interactions with the solvent. Solvent effects on the spectral parameters were rationalized on the basis of the Kamlet-Taft and Catalán solvatochromic models, in order to quantify the degree of polarity-driven and hydrogen bonding interactions. A comparative discussion of the results predicted by the two models was made. In ground state, the DA1.n probes act as hydrogen bond acceptors. In excited state, hydrogen bonding is less favoured, the solute-solvent interactions being governed by the increasing polarity of the solvent that results in a large bathochromic shift of the emission. A comparison was made with the spectral features previously reported for the corresponding series of bis-dansyl fluorescent probes (2DA1.n).

Hierarchical Zeolite Y Containing Ti and Fe Oxides as Photocatalysts for Degradation of Amoxicillin.

The Ti/hierarchical zeolites Y were obtained by direct and post synthesis methods and loaded with Fe(III) by ion-exchange and impregnation resulting Fe-Ti/hierarchical zeolites Y photocatalysts. The synthesized materials were characterized by XRD, SEM microscopy, N2 physical adsorption, Raman, UV-Vis and XPS and EPR spectroscopy. XRD patterns evidenced the crystalline structure of the zeolite Y in all materials, excepting the samples with higher Fe content. The presence of anatase was evidenced by XRD and Raman spectroscopy in the samples obtained by impregnation while α-Fe2O3 was depicted in the Raman spectra of the samples with Ti and lower Fe loading. SEM images and N2 adsorption-desorption isotherms confirmed the formation of mesopores together with microporous crystals of zeolite Y. The UV-Vis spectra proved a red-shifted adsorption band for samples with iron. In all these samples XPS shows Fe3+ as oxide on the surface and EPR Fe3+ in tetrahedral coordination. Different variables such as hierarchical structure, amount of iron, catalyst loading, concentration of pollutant solution, pH value were studied to estimate their effects on performances of photocatalysts in degradation of amoxicillin from aqueous solution in UV and Visible light. A higher adsorption capacity and degradation efficiency of amoxicillin (100%) was noticed for hierarchical materials, especially for higher iron oxide loaded samples.

Obstrucción digestiva alta secundaria a prolapso transpilórico de angiolipoma gástrico / Upper gastrointestinal tract obstruction secondary to transpyloric prolapse of a gastric angiolipoma

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Acute anterograde intussusception as a late complication of distal gastric bypass.

Small bowel intussusception is an uncommon cause of adult intestinal obstruction after gastric bypass for morbid obesity. It usually affects the Roux or the common limb at the jejunojejunostomy site and is mainly retrograde. An altered motility of the Roux limb seems to be the main explanation for its developement. We report the case of a patient with a late acute anterograde intussusception after a previous distal Roux-en-Y gastric bypass. Clinical, radiological and operative findings are presented and surgical solutions described in the literature are reviewed.

Acute abdomen for lymphangioma of the small bowel mesentery: a case report and review of the literature.

Systemic lupus erithematosus (SLE) is an autoimmune disease with multiorgan involvement caused principally by vasculitis of small vessels. The gastrointestinal tract is one of the most frequently affected by SLE, with abdominal pain as the most common symptom. An early diagnosis and treatment of lupus enteritis is essential to avoid complications like hemorrhage or perforation, with up to 50 % of mortality rate. However, differential diagnosis sometimes is difficult, especially with other types of gastrointestinal diseases as digestive involvement of antiphospholipid syndrome (APS), moreover when both entities may coexist. We describe the case of a patient with both diseases that was diagnosed with lupus enteritis and treated with steroid therapy; the patient had an excellent response.

Abdomen agudo por linfangioma mesentérico. Presentación de un caso clínico y revisión de la literatura / Acute abdomen for lymphangioma of the small bowel mesentery: A case report and review of the literature

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Laparoscopic sleeve gastrectomy in patients over 60 years: impact of age on weight loss and co-morbidity improvement.

BACKGROUND: Advanced age has traditionally been considered a relative contraindication to bariatric surgery due to increased perioperative risk and less weight loss. However, it is now being reconsidered in older patients after encouraging results in recent series and the increasing life expectancy. We compared operative and postoperative outcomes of laparoscopic sleeve gastrectomy in patients over 60 years with outcomes in younger patients. We also, analyzed the effect of bariatric surgery on improvement and resolution of co-morbidities in the older group. METHODS: From November 2008 to November 2013, 130 patients underwent laparoscopic sleeve gastrectomy. Of these, 28 patients (21.5%) were 60 years or older. Outcomes in terms of perioperative complications, short-term and medium-term weight loss, remission or improvement of co-morbidities and medication requirements were extracted from our prospective database. RESULTS: Short-term mortality was 0% and 30-day complication rate was similar in both groups (17.9% versus 17.6% according to Clavien-Dindo classification). At 12 months postsurgery, older patients had lost 49% percent of excess weight compared to 60% in the younger group (P = 0.012). At 2 years, the results were 45% versus 60%, respectively, with P = 0.015. At least 1 major co-morbidity improved in 65.2% of older patients. Before surgery, the older group took an average of 4.3 medications compared to 2.7 at 1 year after surgery (P<0.001). CONCLUSION: Laparoscopic sleeve gastrectomy is a safe and effective treatment for morbid obesity in people over 60 years, although younger patients show greater weight loss. Daily medication requirements and co-morbidities decrease significantly in older patients after this procedure.

Tratamiento percutáneo de una obstrucción tumoral de asa aferente de hepaticoyeyunostomía / Percutaneous treatment of a tumour obstruction of the afferent loop of a hepaticojejunostomy

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La influencia del tipo de abordaje torácico sobre el desarrollo de complicaciones respiratorias tras la esofagectomía / Influence of the type of thoracic access on postesophagectomy respiratory complications

INTRODUCCIÓN: Revisión sistemática de la literatura con el objetivo de determinar diferencias entre el abordaje torácico mínimamente invasivo y por toracotomía tradicional para la esofagectomía por cáncer de esófago, en términos de complicaciones respiratorias. MÉTODOS: La búsqueda se ha realizado a través de las bases de datos Medline y Cochrane Library, identificando los estudios que comparaban las 2 variantes técnicas mencionadas, independientemente del tipo de abordaje a nivel abdominal (laparotomía/laparoscopia). Se seleccionaron aquellos estudios que describían las complicaciones respiratorias desglosadas por categorías y en datos absolutos. Se excluyeron los estudios en que se consideraba la minitoracotomía en el grupo de abordaje torácico mínimamente invasivo. Los criterios de selección fueron: consideramos los estudios en los que se describieron las complicaciones respiratorias desglosadas (9 en total) y analizamos las complicaciones más frecuentes (infecciones respiratorias, insuficiencia respiratoria y derrame pleural). RESULTADOS: Seleccionamos 9 estudios (un ensayo clínico prospectivo y aleatorizado, y 8 estudios de casos y controles) totalizando 1.190 pacientes, de los cuales 1.167 fueron intervenidos por cáncer de esófago, 482 pacientes por toracotomía y 708 por toracoscopia. En 3 estudios se encontraron definiciones de las infecciones respiratorias y la estratificación por gravedad de las complicaciones descritas se encontró en un estudio. Las complicaciones más frecuentes y que permitieron realizar un metaanálisis fueron: las infecciones respiratorias, el derrame pleural y la insuficiencia respiratoria. No se identificaron diferencias estadísticas significativas entre los 2 abordajes en el análisis global en cuanto a la tasa de complicaciones respiratorias mencionadas. DISCUSIÓN: El tipo de abordaje torácico (toracotomía o toracoscopia) no parece influir de forma significativa en el desarrollo de complicaciones respiratorias postesofagectomía por cáncer. Sin embargo, el diseño de los estudios analizados, los criterios de definición heterogéneos y la ausencia de una estratificación adecuada de las complicaciones hacen cuestionable esta constatación. Se necesitan más ensayos clínicos prospectivos y aleatorizados y un consenso en cuanto a la forma de definir las complicaciones respiratorias postoperatorias postesofagectomía

INTRODUCTION: A systematic review of the literature was performed with the aim to determine differences in the rate of respiratory complications after esophagectomy for esophageal cancer using minimally invasive access vs traditional thoracic access. METHODS: A literature search was performed using Medline and Cochrane Library, identifying studies that compared the 2 types of thoracic access, regardless of the type of abdominal access (laparotomy/laparoscopy). The studies selected described respiratory complications in absolute numbers and different categories. Studies that considered minithoracotomy as a minimally invasive technique were excluded. Inclusion criteria were: studies decribing the different types of respiratory complications (9 in total), and analysing the most common complications: respiratory infection, respiratory failure and pleural effusion. RESULTS: Nine studies were selected (one prospective randomized trial and 8 case control studies) including 1,190 patients, 1,167 of which were operated on for esophageal cancer: 482 patients by thoracotomy and 708 by thoracoscopy. Three studies included definitions of respiratory complications, and one stratified them. The more frequent complications that allowed a meta-analysis were: respiratory infections, pleural effusion, and respiratory failure. No significant differences were found between the 2 types of access in the global analysis. DISCUSSION: The type of thoracic access (thoracotomy or thoracoscopy) does not seem to influence the development of respiratory complications after esophagectomy for cancer. However, the design of the studies analysed, the absence of clear definitions and stratification of the complications makes this conclusion questionable. A consensus on the definition of complications and further prospective randomized clinical trials are necessary

[Influence of the type of thoracic access on postesophagectomy respiratory complications]. / La influencia del tipo de abordaje torácico sobre el desarrollo de complicaciones respiratorias tras la esofagectomía.

INTRODUCTION: A systematic review of the literature was performed with the aim to determine differences in the rate of respiratory complications after esophagectomy for esophageal cancer using minimally invasive access vs traditional thoracic access. METHODS: A literature search was performed using Medline and Cochrane Library, identifying studies that compared the 2 types of thoracic access, regardless of the type of abdominal access (laparotomy/laparoscopy). The studies selected described respiratory complications in absolute numbers and different categories. Studies that considered minithoracotomy as a minimally invasive technique were excluded. Inclusion criteria were: studies decribing the different types of respiratory complications (9 in total), and analysing the most common complications: respiratory infection, respiratory failure and pleural effusion. RESULTS: Nine studies were selected (one prospective randomized trial and 8 case control studies) including 1,190 patients, 1,167 of which were operated on for esophageal cancer: 482 patients by thoracotomy and 708 by thoracoscopy. Three studies included definitions of respiratory complications, and one stratified them. The more frequent complications that allowed a meta-analysis were: respiratory infections, pleural effusion, and respiratory failure. No significant differences were found between the 2 types of access in the global analysis. DISCUSSION: The type of thoracic access (thoracotomy or thoracoscopy) does not seem to influence the development of respiratory complications after esophagectomy for cancer. However, the design of the studies analysed, the absence of clear definitions and stratification of the complications makes this conclusion questionable. A consensus on the definition of complications and further prospective randomized clinical trials are necessary.