Integration of stable ionic liquid-based nanofluids into polymer membranes. Part I: Membrane synthesis and characterization

In this work, polymeric membranes functionalized with ionic liquids (ILs) and exfoliated graphene nanoplatelets (xGnP) were developed and characterized. These membranes based on graphene ionanofluids (IoNFs) are promising materials for gas separation. The stability of the selected IoNFs in the polymer membranes was determined by thermogravimetric analysis (TGA). The morphology of membranes was characterized using scanning electron microscope (SEM) and interferometric optical profilometry (WLOP). SEM results evidence that upon the small addition of xGnP into the IL-dominated environment, the interaction between IL and xGnP facilitates the migration of xGnP to the surface, while suppressing the interaction between IL and Pebax®1657. Fourier transform infrared spectroscopy (FTIR) was also used to determine the polymer?IoNF interactions and the distribution of the IL in the polymer matrix. Finally, the thermodynamic properties and phase transitions (polymer-IoNF) of these functionalized membranes were studied using differential scanning calorimetry (DSC). This analysis showed a gradual decrease in the melting point of the polyamide (PA6) blocks with a decrease in the corresponding melting enthalpy and a complete disappearance of the crystallinity of the polyether (PEO) phase with increasing IL content. This evidences the high compatibility and good mixing of the polymer and the IoNFAuthors fully acknowledge the financial support received from Project KET4F-Gas-SOE2/P1/P0823, which is co-financed by the European Regional Development Fund within the framework of Interreg Sudoe Programme and project PID2019-105827RB-I00–Agencia Estatal de Investigación, Spain. F.P. acknowledges the postdoctoral fellowship (FJCI-2017-32884 Juan de la Cierva Formación) awarded by the Spanish Ministry of Science, Innovation and Universities. This work was also supported by the Associate Laboratory for Green Chemistry LAQV (financed by national funds from FCT/MCTES, UIDB/50006/2020)

Aggregation and phase equilibria of fluorinated ionic liquids

Grant SFRH/BD/100563/2014. IF/00190/2014 . IF/00210/2014. PTDC/EQU-EQU/29737/2017. PTDC/QEQ-FTT/3289/2014. IF/00210/2014/CP1244/CT0003. UID/QUI/50006/2019. POCI-01-0145-FEDER - 007265.In this work a specific family of ionic liquids, denominated fluorinated ionic liquids, with fluorine tags equal or longer than four carbon atoms, are fully characterized in order to understand their solubility and self-aggregation in aqueous solutions. The numerous combinations between cations and anions make these compounds a feasible option for the replacement of traditional and toxic surfactants used in the industrial and biomedical field. In this work, the increment of both hydrogenated and fluorinated side chain lengths, the influence of the cation headgroup (imidazolium and cholinium)as well as the difference between perfluorobutanesulfonate and perfluoropentanoate anions were studied. The liquid-liquid phase equilibria of fluorinated ionic liquids based on the perfluorobutanesulfonate anion with water were carried out. The self-aggregation behaviour of the different fluorinated ionic liquids in aqueous solutions was also determined using conductimetric titration, surface tension measurements and transmission electron microscopy. Several thermodynamic and surface parameters were obtained and used to discuss the aggregation process. These novel characterized fluorinated ionic liquids demonstrate an improved surface activity and aggregation behaviour, driven essentially by the increment of both hydrogenated and fluorinated chain lengths.authorsversionpublishe

Role of age and comorbidities in mortality of patients with infective endocarditis

[Purpose]: The aim of this study was to analyse the characteristics of patients with IE in three groups of age and to assess the ability of age and the Charlson Comorbidity Index (CCI) to predict mortality. [Methods]: Prospective cohort study of all patients with IE included in the GAMES Spanish database between 2008 and 2015.Patients were stratified into three age groups:<65 years,65 to 80 years,and ≥ 80 years.The area under the receiver-operating characteristic (AUROC) curve was calculated to quantify the diagnostic accuracy of the CCI to predict mortality risk. [Results]: A total of 3120 patients with IE (1327 < 65 years;1291 65-80 years;502 ≥ 80 years) were enrolled.Fever and heart failure were the most common presentations of IE, with no differences among age groups.Patients ≥80 years who underwent surgery were significantly lower compared with other age groups (14.3%,65 years; 20.5%,65-79 years; 31.3%,≥80 years). In-hospital mortality was lower in the <65-year group (20.3%,<65 years;30.1%,65-79 years;34.7%,≥80 years;p < 0.001) as well as 1-year mortality (3.2%, <65 years; 5.5%, 65-80 years;7.6%,≥80 years; p = 0.003).Independent predictors of mortality were age ≥ 80 years (hazard ratio [HR]:2.78;95% confidence interval [CI]:2.32–3.34), CCI ≥ 3 (HR:1.62; 95% CI:1.39–1.88),and non-performed surgery (HR:1.64;95% CI:11.16–1.58).When the three age groups were compared,the AUROC curve for CCI was significantly larger for patients aged <65 years(p < 0.001) for both in-hospital and 1-year mortality. [Conclusion]: There were no differences in the clinical presentation of IE between the groups. Age ≥ 80 years, high comorbidity (measured by CCI),and non-performance of surgery were independent predictors of mortality in patients with IE.CCI could help to identify those patients with IE and surgical indication who present a lower risk of in-hospital and 1-year mortality after surgery, especially in the <65-year group

Nanofluidos de grafeno : propiedades viscoelásticas e termofísicas

Graphene, a single-atom-thick sheet of hexagonally arranged sp2-bonded carbon atoms, has attracted much attention since it was experimentally isolated by Novoselov and Geim ten years ago. The two dimensional (2D) material exhibits exceptionally high crystal and electronic quality, and it has already revealed a plethora of amazing physical properties and potential applications. This includes high values of Young’s modulus, fracture strength, mobility of charge carriers, and specific surface area, plus fascinating transport phenomena such as the quantum Hall effect. Recent research reveals that the in-plane thermal conductivity of a suspended single-layer graphene is as high as 5200 W/mK4. Because single layer graphene sheets are finite and dimensional limitations influence the electronic properties of graphene, graphene-based materials can be categorized according to the dimensions of sheets in the parallel and perpendicular directions of the layers. Among them, exfoliated graphite nanoplatelets (xGnP) (10-100 graphene layers, 3-30 nm thick), which combine the layered structure and low price of nanoclays with the superior mechanical, electrical and thermal properties of carbon nanotubes, are very cost effective and can simultaneously provide a multitude of physical and chemical property enhancements. The properties of xGnP are independent of the number of layers and show similar electro-chemical behavior to graphene. Although the number of articles on xGnP has increased, data on their thermodynamic properties, thermophysical description, and molecular modeling properties are relatively scarce. Nanofluids, which are suspensions of nanoparticles in fluids, have promising potential applications in microelectronics, energy supply and transportation because of their intriguing properties such as the increased thermal conductivity in certain cases, long-term stability, and prevention of clogging in microchannels. The nanoscale size range of the suspended particles produces unexpected behaviour in some cases for thermophysical and transport properties. In fact it was the initial report of unusual thermal conductivity enhancements what boosted research on nanofluid characterization. After a certain rush period, these enhancements were demonstrated not to be so general nor so high. Nevertheless, the discussion about which are the heat and mass transfer mechanisms for this type of systems represents an open and active debate, and some nanofluids do exhibit unexpected non classical thermophysical and elastic properties. This is an amazing and poorly explored field of research, and contributions on the rigorous experimental determination of the thermophysical and transport properties characterization of these new xGnP nanofluids are essential to determine their feasibility in technical applications involving for instance heat dissipation in microfluidics. This is the context where the present PhD is proposed, according to the objectives and methodology explained in the following.El grafeno, una hoja de un átomo de espesor de átomos de carbono unidos por enlaces hexagonales sp2, ha atraído mucha atención desde que fue experimentalmente aislado por Novoselov y Geim hace diez años. El material bidimensional (2D) exhibe una calidad cristalina y electrónica excepcionalmente alta, y ya ha revelado una plétora de asombrosas propiedades físicas y aplicaciones potenciales. Esto incluye altos valores del módulo de Young, resistencia a la fractura, movilidad de los portadores de carga y área de superficie específica, además de fascinantes fenómenos de transporte como el efecto Hall cuántico. Investigaciones recientes revelan que la conductividad térmica en un plano de grafeno suspendido de una sola capa es tan alta como 5200 W/mK4. Debido a que las capas de grafeno de capa única poseen limitaciones finitas y dimensionales, esto influye en sus propiedades electrónicas, y los materiales a base de grafeno pueden categorizarse de acuerdo con las dimensiones de las hojas en las direcciones paralela y perpendicular de las capas. Entre ellos, las nanopartículas de grafito exfoliado (xGnP) (10-100 capas de grafeno, 3-30 nm de espesor), que combinan la estructura en capas y el bajo precio de nanocerámicas con propiedades mecánicas, eléctricas y térmicas superiores de los nanotubos de carbono, son muy rentables y pueden proporcionar simultáneamente una multitud de mejoras de propiedades físicas y químicas. Las propiedades de xGnP son independientes del número de capas y muestran un comportamiento electroquímico similar al del grafeno. Aunque el número de artículos sobre xGnP ha aumentado, los datos sobre sus propiedades termodinámicas, descripción termofísica y propiedades de modelado molecular son relativamente escasos. Los nanofluidos, que son suspensiones de nanopartículas en fluidos, tienen potenciales aplicaciones potenciales en microelectrónica, suministro de energía y transporte debido a sus propiedades intrigantes como el aumento de la conductividad térmica en ciertos casos, la estabilidad a largo plazo y la prevención de la obstrucción en microcanales. El rango de tamaño nanométrico de las partículas en suspensión produce un comportamiento inesperado en algunos casos para propiedades termofísicas y de transporte. De hecho, fue el informe inicial de las mejoras inusuales de conductividad térmica lo que impulsó la investigación sobre la caracterización de nanofluidos. Después de un cierto período de euforia inicial, estas mejoras demostraron no ser tan generales ni tan elevadas. Sin embargo, la discusión acerca de cuáles son los mecanismos de transferencia de calor y masa para este tipo de sistemas representa un debate científico abierto y activo, y algunos nanofluidos exhiben propiedades termofísicas y elásticas inesperadas y claramente no clásicas. Este es un campo de investigación apasionante y poco explorado, y las contribuciones sobre la determinación experimental rigurosa de la caracterización termofísica y de propiedades de transporte de estos nuevos nanofluidos xGnP son esenciales para determinar su viabilidad en aplicaciones técnicas que implican por ejemplo disipación de calor en microfluídica. Este es el contexto en el que se propone la presente Tesis de Doctorado, de acuerdo con los objetivos y metodología explicados a continuación.O grafeno, unha folla dun átomo de espesor de átomos de carbono unidos por enlaces hexagonais sp2, ten atraído moita atención dende que foi experimentalmente aislado por Novoselov e Geim fai dez anos. O material bidimensional (2D) exhibe unha calidade cristalina e electrónica excepcionalmente alta, e xa ten revelado unha plétora de asombrosas propiedades físicas e aplicacións potenciais. Isto inclúe altos valores do módulo de Young, resistencia á fractura, mobilidade de portadores de carga e área de superficie específica, ademáis de fascinantes fenómenos de transporte coma o efecto Hall cuántico. Investigacións recentes revelan que a conductividade térmica nun plano de grafeno suspendido dunha sola capa é tan alta coma 5200 W/mK4. Debido a que as capas de grafeno de capa única poseen limitacións finitas e dimensionais, isto inflúe nas súas propiedades electrónicas, e os materiais a base de grafeno poden categorizarse dacordo coas dimensións das follas nas direccións paralela e perpendicular das capas. Entre eles, as nanopartículas de grafito exfoliado (xGnP) (10-100 capas de grafeno, 3-30 nm de espesor), que combinan a estructura en capas e o baixo prezo de nanocerámicas con propiedades mecánicas, eléctricas y térmicas superiores dos nanotubos de carbono, son moi rentables e poden proporcionar simultáneamente unha multitude de melloras de propiedades físicas e químicas. As propiedades de xGnP son independentes do número de capas e amosan un comportamento electroquímico similar ó do grafeno. Aínda que o número de artigos sobre xGnP aumentou moito, os datos sobre as súas propiedades termodinámicas, descripción termofísica e propiedades de modelado molecular son relativamente escasos. Os nanofluidos, que son suspensións de nanopartículas en fluidos, teñen potenciais aplicacións en microelectrónica, suministro de enerxía e transporte debido ás súas propiedades intrigantes coma o aumento da conductividade térmica en certos casos, a estabilidade a longo prazo e a prevención de obstrucción en microcanais. O rango de tamaño nanométrico das partículas en suspensión produce un comportamento inesperado nalgúns casos para propiedades termofísicas e de transporte. De feito, foi o informe inicial das melloras inusuais de conductividade térmica o que impulsou a investigación sobre a caracterización de nanofluidos. Despois dun certo período de euforia inicial, estas melloras amosaron non ser tan xerais nin tan elevadas. Nembargantes, a discusión acerca de cales son os mecanismos de transferencia de calor e masa para este tipo de sistemas representa un debate científico aberto e activo, e algúns nanofluidos exhiben propiedades termofísicas e elásticas inagardadas e claramente non clásicas. Este é un campo de investigación apaixoante e pouco explorado, e as contribucións sobre a determinación experimental rigurosa da caracterización termofísica e de propiedades de transporte destes novos nanofluidos xGnP son esenciais para determinar a súa viabilidade en aplicacións técnicas que implican por exemplo disipación de calor en microfluídica. Este é o contexto no que se propon la presente Tese de Doutoramento, dacordo cos obxectivos e metodoloxía explicados a continuación

Extraction and characterization of gelatin from skin by-products of seabream, seabass and rainbow trout reared in aquaculture

16 pages, 6 figures, 6 tables.-- This is an open access article distributed under the Creative Commons Attribution LicenseThe expansion of fish filleting, driven by the increasing demand for convenience food, concomitantly generates a rising amount of skinning by-products. Current trends point to a growing share of aquaculture in fish production, so we have chosen three established aquaculture species to study the properties of gelatin extracted from their skin: rainbow trout, commonly filleted; and seabass and seabream, marketed whole until very recently. In the first case, trout skin yields only 1.6% gelatin accompanied by the lowest gel strength (96 g bloom), while yield for the other two species exceeds 6%, and gel strength reaches 181 and 229 g bloom for seabass and seabream, respectively. These results are in line with the proportion of total imino acids analyzed in the gelatin samples. Molecular weight profiling shows similarities among gelatins, but seabass and seabream gelatins appear more structured, with higher proportion of β-chains and high molecular weight aggregates, which may influence the rheological properties observed. These results present skin by-products of seabream, and to a minor extent seabass, as suitable raw materials to produce gelatin through valorization processesThis research was funded by the GAIN project (EU, Horizon 2020 Framework Research and Innovation Programme under GA n. 773330), and Xunta de Galicia (Grupos de Potencial Crecimiento, IN607B 2021/11)Peer reviewe

Determination of transport properties of glycol-based nanofluids derived from surface functionalized graphene

Suspensions of nanometric-sized graphene platelets have been proposed recently as potential heat exchange working fluids, due to their remarkably enhanced thermal profile. Nevertheless, their use presents serious long-term stability issues. Due to this limitation, the nanoplatelets surface chemical functionalization has been postulated as a promising alternative to solve this problem. In this work, graphene nanoplatelets were functionalized following an oxidation-reduction process, and then dispersed in glycol as base fluid. The nanoparticles chemical profile was determined using XPS (x-ray photoelectron spectroscopy). The thermo-physical properties characterization of these nanofluids was performed by determining their viscosity and thermal conductivity, because of their impact on practical applications related with fluid flow and heat transfer. The effect of temperature and shearing time on viscosity were analyzed. Viscosity was measured with a stress-controlled rheometer. All samples show shear-thinning behavior with a very remarkable influence of temperature in their viscoelastic profile.Ministerio de Economía y Competitividad (España) | Ref. FIS2015-68910-PEuropean Commission | Ref. SOE2/P1/P082

Production and Physicochemical Characterization of Gelatin and Collagen Hydrolysates from Turbot Skin Waste Generated by Aquaculture Activities

19 pages, 8 figures, 4 tables.-- This is an open access article distributed under the Creative Commons Attribution LicenseRising trends in fish filleting are increasing the amount of processing by-products, such as skins of turbot, a flatfish of high commercial value. In line with circular economy principles, we propose the valorization of turbot skins through a two-step process: initial gelatin extraction described for the first time in turbot, followed by hydrolysis of the remaining solids to produce collagen hydrolysates. We assayed several methods for gelatin extraction, finding differences in gelatin properties depending on chemical treatment and temperature. Of all methods, the application of NaOH, sulfuric, and citric acids at 22 °C results in the highest gel strength (177 g), storage and loss moduli, and gel stability. We found no relation between mechanical properties and content of pyrrolidine amino acids, but the best performing gelatin displays higher structural integrity, with less than 30% of the material below 100 kDa. Collagen hydrolysis was more efficient with papain than alcalase, leading to a greater reduction in Mw of the hydrolysates, which contain a higher proportion of essential amino acids than gelatin and show high in vitro anti-hypertensive activity. These results highlight the suitability of turbot skin by-products as a source of gelatin and the potential of collagen hydrolysates as a functional food and feed ingredient.This research was funded by GAIN project (EU, Horizon 2020 Framework Research and Innovation Programme under GA n. 773330), and Xunta de Galicia (Grupos de Potencial Crecimiento, IN607B 2021/11Peer reviewe

Combined Gelatin-Chondroitin Sulfate Hydrogels with graphene nanoparticles

10 pages, 5 figures, 3 tablesCreating flexible, high-strength hydrogels from harmless, low-cost natural polymers is an area of intense research today due to their potential applications in the biomedical field, which demands materials with ambivalent physicochemical features. In particular, great efforts were devoted to the preparation of sustainable biohydrogels, composed of hydrophilic networks of renewable, biocompatible, biodegradable, and low-cost biopolymers. Bionanocomposites are a promising synthetic approach to combine specific multifunctional materials with targeted physicochemical properties. Novel bionanocomposite hydrogels were designed by combining both chondroitin sulfate (CS) as well as gelatin (GE) obtained from the waste generated by the fish industries to form double fibre networks with tailored properties. In addition, hybrid bionanocomposites were achieved by introducing graphene nanoparticles (xGnP) into the double fibrillar network (GE/CS) to enhance the physicochemical properties. The bionanocomposite nanostructures were characterized by Fourier transform infrared spectroscopy (FTIR), differential scanning calorimeter (DSC) while their rheological properties and thermal stability were determined by rheological and thermogravimetric analyses (TGA), respectively. The likely interactions between CS and gelatin in the GE/CS hydrogel network were proved by ATR-FTIR spectroscopy. The incorporation of xGnP improved the mechanical properties of the GE/CS fibrillary network by an order of magnitude in the shear storage modulus. Eventually, the generated bionanocomposites hydrogels and bionanocomposite hybrid hydrogels have promising potential for applications in many biomedical fields, including drug delivery and tissue engineering by mimicking tissue extracellular matrix components such as the gelatin for collagen and the CS in the cartilageThe authors acknowledge the financial support received from Project KET4F-Gas-SOE2/P1/P0823, which is co-financed by the European Regional Development Fund within the framework of Interreg Sudoe Programme and project PID2019-105827RB-I00–Agencia Estatal de Investigación, SpainPeer reviewe

Characterization of tuna gelatin-based hydrogels as a matrix for drug delivery

The skin of yellowfin tuna is one of the fishery industry solid residues with the greatest potential to add extra value to its circular economy that remains yet unexploited. Particularly, the high collagen content of fish skin allows generating gelatin by hydrolysis, which is ideal for forming hydrogels due to its biocompatibility and gelling capability. Hydrogels have been used as drug carriers for local administration due to their mechanical properties and drug loading capacity. Herein, novel tuna gelatin hydrogels were designed as drug vehicles with two structurally different antitumoral model compounds such as Doxorubicin and Crocin to be administrated locally in tissues with complex human anatomies after surgical resection. The characterization by gel permeation chromatography (GPC) of purified gelatin confirmed their heterogeneity composition, exhibiting three major bands that correspond to the β and α chains along with high molecular weight species. In addition, the Fourier Transform Infrared (FT-IR) spectra of gelatin probed the secondary structure of the gelatin showing the simultaneous existence of α helix, β sheet, and random coil structures. Morphological studies at different length scales were performed by a multi-technique approach using SAXS/WAXS, AFM and cryo-SEM that revealed the porous network formed by the interaction of gelatin planar aggregates. In addition, the sol-gel transition, as well as the gelation point and the hydrogel strength, were studied using dynamic rheology and differential scanning calorimetry. Likewise, the loading and release profiles followed by UV-visible spectroscopy indicated that the novel gelatin hydrogels improve the drug release of Doxorubicin and Crocin in a sustained fashion, indicating the structure-function importance in the material composition.Xunta de Galicia | Ref. IN607B 2021/1

Characterization of Gelatin and Hydrolysates from Valorization of Farmed Salmon Skin By-Products

18 pages, 8 tables, 6 figures.-- This is an open access article distributed under the Creative Commons Attribution LicenseSalmon processing commonly involves the skinning of fish, generating by-products that need to be handled. Such skin residues may represent valuable raw materials from a valorization perspective, mainly due to their collagen content. With this approach, we propose in the present work the extraction of gelatin from farmed salmon and further valorization of the remaining residue through hydrolysis. Use of different chemical treatments prior to thermal extraction of gelatin results in a consistent yield of around 5%, but considerable differences in rheological properties. As expected from a cold-water species, salmon gelatin produces rather weak gels, ranging from 0 to 98 g Bloom. Nevertheless, the best performing gelatins show considerable structural integrity, assessed by gel permeation chromatography with light scattering detection for the first time on salmon gelatin. Finally, proteolysis of skin residues with Alcalase for 4 h maximizes digestibility and antihypertensive activity of the resulting hydrolysates, accompanied by the sharpest reduction in molecular weight and higher content of essential amino acids. These results indicate the possibility of tuning salmon gelatin properties through changes in chemical treatment conditions, and completing the valorization cycle through production of bioactive and nutritious hydrolysatesThis research was funded by GAIN project (EU, Horizon 2020 Framework Research and Innovation Programme under GA n. 773330), and Xunta de Galicia (Grupos de Potencial Crecimiento, IN607B 2021/11)Peer reviewe