4,726 research outputs found

    Raman Spectroscopy Techniques for the Detection and Management of Breast Cancer

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    Breast cancer has recently become the most common cancer worldwide, and with increased incidence, there is increased pressure on health services to diagnose and treat many more patients. Mortality and survival rates for this particular disease are better than other cancer types, and part of this is due to the facilitation of early diagnosis provided by screening programmes, including the National Health Service breast screening programme in the UK. Despite the benefits of the programme, some patients undergo negative experiences in the form of false negative mammograms, overdiagnosis and subsequent overtreatment, and even a small number of cancers are induced by the use of ionising radiation. In addition to this, false positive mammograms cause a large number of unnecessary biopsies, which means significant costs, both financially and in terms of clinicians' time, and discourages patients from attending further screening. Improvement in areas of the treatment pathway is also needed. Surgery is usually the first line of treatment for early breast cancer, with breast conserving surgery being the preferred option compared to mastectomy. This type of operation achieves the same outcome as mastectomy - removal of the tumour - while allowing the patient to retain the majority of their normal breast tissue for improved aesthetic and psychological results. Yet, re-excision operations are often required when clear margins are not achieved, i.e. not all of the tumour is removed. This again has implications on cost and time, and increases the risk to the patient through additional surgery. Currently lacking in both the screening and surgical contexts is the ability to discern specific chemicals present in the breast tissue being assessed/removed. Specifically relevant to mammography is the presence of calcifications, the chemistry of which holds information indicative of pathology that cannot be accessed through x-rays. In addition, the chemical composition of breast tumour tissue has been shown to be different to normal tissue in a variety of ways, with one particular difference being a significant increase in water content. Raman spectroscopy is a rapid, non-ionising, non-destructive technique based on light scattering. It has been proven to discern between chemical types of calcification and subtleties within their spectra that indicate the malignancy status of the surrounding tissue, and differentiate between cancerous and normal breast tissue based on the relative water contents. Furthermore, this thesis presents work aimed at exploring deep Raman techniques to probe breast calcifications at depth within tissue, and using a high wavenumber Raman probe to discriminate tumour from normal tissue predominantly via changes in tissue water content. The ability of transmission Raman spectroscopy to detect different masses and distributions of calcified powder inclusions within tissue phantoms was tested, as well as elucidating a signal profile of a similar inclusion through a tissue phantom of clinically relevant thickness. The technique was then applied to the measurement of clinically active samples of bulk breast tissue from informed and consented patients to try to measure calcifications. Ex vivo specimens were also measured with a high wavenumber Raman probe, which found significant differences between tumour and normal tissue, largely due to water content, resulting in a classification model that achieved 77.1% sensitivity and 90.8% specificity. While calcifications were harder to detect in the ex vivo specimens, promising results were still achieved, potentially indicating a much more widespread influence of calcification in breast tissue, and to obtain useful signal from bulk human tissue is encouraging in itself. Consequently, this work demonstrates the potential value of both deep Raman techniques and high wavenumber Raman for future breast screening and tumour margin assessment methods

    Proceedings of the 10th International congress on architectural technology (ICAT 2024): architectural technology transformation.

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    The profession of architectural technology is influential in the transformation of the built environment regionally, nationally, and internationally. The congress provides a platform for industry, educators, researchers, and the next generation of built environment students and professionals to showcase where their influence is transforming the built environment through novel ideas, businesses, leadership, innovation, digital transformation, research and development, and sustainable forward-thinking technological and construction assembly design

    The development of liquid crystal lasers for application in fluorescence microscopy

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    Lasers can be found in many areas of optical medical imaging and their properties have enabled the rapid advancement of many imaging techniques and modalities. Their narrow linewidth, relative brightness and coherence are advantageous in obtaining high quality images of biological samples. This is particularly beneficial in fluorescence microscopy. However, commercial imaging systems depend on the combination of multiple independent laser sources or use tuneable sources, both of which are expensive and have large footprints. This thesis demonstrates the use of liquid crystal (LC) laser technology, a compact and portable alternative, as an exciting candidate to provide a tailorable light source for fluorescence microscopy. Firstly, to improve the laser performance parameters such that high power and high specification lasers could be realised; device fabrication improvements were presented. Studies exploring the effect of alignment layer rubbing depth and the device cell gap spacing on laser performance were conducted. The results were the first of their kind and produced advances in fabrication that were critical to repeatedly realising stable, single-mode LC laser outputs with sufficient power to conduct microscopy. These investigations also aided with the realisation of laser diode pumping of LC lasers. Secondly, the identification of optimum dye concentrations for single and multi-dye systems were used to optimise the LC laser mixtures for optimal performance. These investigations resulted in novel results relating to the gain media in LC laser systems. Collectively, these advancements yielded lasers of extremely low threshold, comparable to the lowest reported thresholds in the literature. A portable LC laser system was integrated into a microscope and used to perform fluorescence microscopy. Successful two-colour imaging and multi-wavelength switching ability of LC lasers were exhibited for the first time. The wavelength selectivity of LC lasers was shown to allow lower incident average powers to be used for comparable image quality. Lastly, wavelength selectivity enabled the LC laser fluorescence microscope to achieve high enough sensitivity to conduct quantitative fluorescence measurements. The development of LC lasers and their suitability to fluorescence microscopy demonstrated in this thesis is hoped to push towards the realisation of commercialisation and application for the technology

    Crystal Structures of Metal Complexes

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    This reprint contains 11 papers published in a Special Issue of Molecules entitled "Crystal Structures of Metal Complexes". I will be very happy if readers will be interested in the crystal structures of metal complexes

    Hydrogen-bonding receptors for anion recovery in a capacitive deionisation system

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    Receptors are ubiquitous throughout nature and are found heavily within biological systems. This has led to synthetic supramolecular chemists to modify or develop analogous mimics of these receptors with high affinity and specificity for a range of target compounds, for potential commercial use. One group of particular interest are receptors that function through the formation of hydrogen bonds to the guest species. This class of receptor has been shown to have a range of different structural geometries and binding motifs, that allow for the sequestration of a number of different species. In the context of this work, anionic hydrogen-bonding receptors, specifically for ‘phosphate’- in most cases dihydrogenphosphate- and bicarbonate are of interest. Phosphate is an integral part of the DNA backbone, however a organophosphorus containing compounds also comprise a large group of chemical weapons which can have a devasting impact on the bodies ability to function. Chemical weapon compounds, such as sarin and Novichok, are based on the functionalisation of a central phosphate core which can be biotransformed into a highly potent active species within the body. Phosphate is also an essential component of plant fertilizers and is used on a huge scale in order to maintain global food security. However, phosphate loss as a consequence of agricultural run-off leads to reduced availability of essential minerals as well as large scale eutrophication. One such method that could be utilised for the recovery of phosphate is electrochemical capacitive deionisation. The principle and idea of capacitive deionisation has been around since the late 1960’s to early 1970’s and has been shown to be a suitable method for the desalination of low-to-medium salinity input streams. The purpose of the work within this thesis was to modify and synthesise receptors that could be covalently attached to porous carbon electrodes and impart selectivity to a capacitive deionisation system. In Chapter 1, the importance of ‘phosphate’, biologically and commercially is addressed before an in depth look at some of the phosphate specific hydrogen bonding receptors that have been reported in the literature. The design of a successful hydrogen bonding receptor relies on the correct orientation of the binding motifs and the range of structural scaffolds have been shown to be useable. Following this, the electrochemical principles of capacitive deionisation and its suitability for the recovery of phosphate are detailed, including some examples of capacitive deionisation set-ups and the overall processes involved. Chapter 2 details the theory of the techniques used throughout this thesis, which include, but not limited to, 1H and 13C NMR for the structural elucidation of the synthesised receptors and cyclic voltammetry which was used for the attachment of organic groups to an electrode. The historical and theoretical background established in Chapters 1 and 2 will lead into the work undertaken in Chapters 3-5. Chapter 3 focusses on the first of three hydrogen bonding receptors synthesised. Building upon previous work within the field, two neutral indole-based receptors were modified to include two different potential attachment points for the electrode- a carboxylic acid and an alkyne. Following the successful synthesis of the alkyne-based receptor, 1H NMR titrations were used to confirm the affinity of the new receptor for dihydrogenphosphate. Chapter 4 introduces the second anion of interest, bicarbonate. The underlying principles for hydrogen bonding are the same for bicarbonate, as in phosphate, however a different receptor was synthesised. The carbazole receptor synthesised contained free amine groups that were proposed to act as points of attachment to an already surface bound organic spacer group. 1H NMR titrations are once again used to determine the affinity of the receptor for the bicarbonate anion. Finally, Chapter 5 introduces the second of the dihydrogenphosphate-specific receptors, this time based on the amino acid leucine. UVVis titrations with a number of different anions were used to determine the affinity of the receptor. Within this chapter, methods for the attachment of organic groups are detailed including the electroreduction of 4-nitrobenzene diazonium and the direct oxidation of the alkyne

    A comprehensive review of primary strategies for tar removal in biomass gasification

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    In the current energy scenario, the production of heat, power and biofuels from biomass has become of major interest. Amongst diverse thermochemical routes, gasification has stood out as a key technology for the large-scale application of biomass. However, the development of biomass gasification is subjected to the efficient conversion of the biochar and the mitigation of troublesome by-products, such as tar. Syngas with high tar content can cause pipeline fouling, downstream corrosion, catalyst deactivation, as well as adverse impact on health and environment, which obstruct the commercialization of biomass gasification technologies. Since the reduction of tar formation is a key challenge in biomass gasification, a comprehensive overview is provided on the following aspects, which particularly include the definition and complementary classifications of tar, as well as possible tar formation and transformation mechanisms. Moreover, the adverse effects of tar on downstream applications, human health or environment, and tar analyzing techniques (online and off-line) are discussed. Finally, the primary tar removal strategies are summarized. In this respect, the effect of key operation parameters (temperature, ER and S/B), catalysts utilization (natural and supported metal catalysts) and the improvement of reactor design on tar formation and elimination was thoroughly analyzed.This work was carried out with the financial support from Spanish Ministries of Science, Innovation and Universities (RTI2018-098283-J-I00 (MCIU/AEI/FEDER, UE)) and Science and Innovation (PID2019-107357RB-I00 (MCIU/AEI/FEDER, UE) and TED2021-132056B-I00 (MCI/AEI/FEDER, UE)) and the Basque Government (IT1645-22). Moreover, this project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No 823745

    Evaluating the anticipated outcomes of MRI seizure image from open-source tool- Prototype approach

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    Epileptic Seizure is an abnormal neuronal exertion in the brain, affecting nearly 70 million of the world's population (Ngugi et al., 2010). So many open-source neuroimaging tools are used for metabolism checkups and analysis purposes. The scope of open-source tools like MATLAB, Slicer 3D, Brain Suite21a, SPM, and MedCalc are explained in this paper. MATLAB was used by 60% of the researchers for their image processing and 10% of them use their proprietary software. More than 30% of the researchers use other open-source software tools with their processing techniques for the study of magnetic resonance seizure image

    Multi-product biorefinery from bay tree pruning for advanced materials production and application

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    Debido a los desafíos económicos y ambientales a los que se enfrenta la sociedad actual, los estados miembros de las Naciones Unidas propusieron en 2015 los 17 Objetivos del Desarrollo Sostenible (ODS). Estos objetivos se centran en promover formas para lograr la sostenibilidad en todas las áreas posibles (agua, energía, clima, industrias, economía, ciencia y tecnología). De esta manera, se hace inminente la necesidad de transición hacia la bioeconomía. La bioeconomía desempeña un papel importante para alcanzar el desarrollo sostenible, ya que su principal objetivo es que la economía actual se base en el uso de recursos renovables que puedan ser convertidos en productos de alto valor añadido. El agotamiento de los recursos fósiles, así como la fluctuación en los precios del petróleo y los problemas de contaminación ambiental, exigen la búsqueda de una nueva perspectiva en la que el uso de recursos renovables sea la base. En este sentido, las biorrefinerías de materiales lignocelulósicos surgen como una solución brillante. En los sistemas de biorrefinería se valorizan diferentes tipos de residuos lignocelulósicos para obtener productos útiles, eficientes y valiosos que ayuden a lograr el tan deseado desarrollo sostenible. De esta forma, la presente Tesis Doctoral ha abordado diferentes caminos para la valorización de los residuos de la poda de laurel (Laurus nobilis L.) desde el punto de vista de la biorrefinería, mediante su transformación, fraccionamiento y aplicación en la preparación de nuevos materiales y productos de alto valor añadido. La modificación química de los residuos lignocelulósicos mediante reacciones de licuefacción ha surgido en los últimos años como una técnica novedosa para la preparación de materiales compuestos, acrilatos y poliuretanos basados en compuestos naturales. Los polioles que se utilizan comúnmente en la industria del poliuretano son de origen petroquímico. Por lo tanto, la preparación de polioles naturales con características similares a los derivados del petróleo podría abrir un camino alternativo y sostenible en el mercado de los poliuretanos. En este sentido, en la Publicación I de esta Tesis Doctoral se describe la síntesis de polioles a partir de residuos de la poda de laurel, sin fraccionamiento previo, y su aplicación para la preparación de espumas de poliuretano aislantes. El poliol obtenido demostró propiedades similares (número de grupos hidroxilo, viscosidad y peso molecular) o incluso mejores que los polioles disponibles actualmente en el mercado, además de reportar un alto rendimiento de licuefacción. Por tanto, el poliol era perfectamente aplicable para la preparación de las mencionadas espumas. Las espumas aislantes se prepararon teniendo en cuenta varios parámetros que suelen influir en la estructura final de estos materiales: el tipo de diisocianato empleado (MDI o TDI) y la adición de agua como agente espumante físico. Según los resultados obtenidos, las espumas preparadas con TDI mostraron una formulación óptima a una relación molar NCO/OH (RNCO/OH) de 1,1 (40% en peso de poliol de residuos de la poda de laurel y sin la adición del agente espumante) en términos de densidad aparente y propiedades mecánicas (resistencia a la compresión y módulo de Young). En el caso de las espumas preparadas con MDI, se encontró que la formulación óptima era de RNCO/OH 0,63 (50% en peso de poliol de residuos de la poda de laurel y con adición del agente espumante). Todas las espumas formuladas tenían una morfología de celdas pequeñas y cerradas y una mayor estabilidad térmica con la presencia del poliol sintetizado. Los resultados obtenidos en este estudio han permitido sugerir al poliol de residuos de la poda de laurel como un sustituto adecuado de los poliuretanos empleados habitualmente. Por otro lado, tradicionalmente, la aplicación más conocida del laurel ha sido a través de su aceite esencial en cocina y farmacia, a pesar de haber demostrado buenos resultados en el tratamiento de enfermedades gracias a sus propiedades antioxidantes. Estos extractos naturales suelen obtenerse mediante extracción convencional Soxhlet, lo que requiere grandes volúmenes de disolvente de extracción, así como tiempos de extracción largos. Yendo un paso más allá, la Publicación II se centra en la optimización de la obtención del extracto natural de las hojas de laurel mediante metodologías de intensificación respetuosas con el medio ambiente. En este sentido, se estableció y aplicó un protocolo de pretratamiento mecanoquímico sobre la muestra que facilitara el proceso de extracción posterior. Este pretratamiento se llevó a cabo evaluando la influencia de diferentes reactivos sólidos (Na2CO3, BaCO3, Li2CO3, CoCO3, K2CO3 y CaCO3) y se comparó con la extracción convencional, así como con otras técnicas novedosas en el campo de la extracción de compuestos bioactivos como el ultrasonidos y la irradiación microondas. Este estudio demostró que el pretratamiento mecanoquímico permitía obtener extractos con contenidos fenólicos comparables a los de la extracción convencional (75,54 GAE/g extracto), con la ventaja de que, para un mismo valor, el tiempo total de extracción se reducía más de 10 veces mediante el uso de la mecanoquímica. Los compuestos principales identificados en el extracto fueron eugenol, metileugenol y elemicina. Aunque las extracciones asistidas por ultrasonidos y microondas resultaron en mayores rendimientos y valores más altos en las propiedades de los extractos evaluadas que las realizadas con pretratamiento mecanoquímico, el presente estudio propone la sustitución de la extracción convencional por la mecanoquímica para obtener el mismo rendimiento, pero de una forma más sostenible. La siguiente aproximación que se abordó para la valorización de los residuos de la poda de laurel fue su fraccionamiento para la obtención una de las fracciones lignocelulósicas presente y posterior conversión en compuestos de alto valor añadido. Así, la Publicación III versa sobre la extracción de polisacáridos (hemicelulosas y almidón) de los residuos de la poda de laurel y su utilización como fuente de azúcares C5 y C6 para la síntesis de levulinato de metilo, molécula de alto valor añadido debido a que se trata de una molécula plataforma para la síntesis de productos químicos relevantes como la γ- valerolactona. La fracción de polisacáridos se obtuvo por extracción hidrotermal (autohidrólisis), determinando las condiciones óptimas mediante un diseño experimental en el que se contemplaron diferentes temperaturas (160, 180, 190 y 200 °C) y tiempos (30, 45, 60 y 75 min). Todas las fracciones obtenidas se caracterizaron para conocer el perfil de carbohidratos, los ácidos fenólicos, las proteínas y la distribución de pesos moleculares. Los polisacáridos obtenidos en las condiciones óptimas (160 °C 45 min) estaban compuestos de una mezcla de 37,87% de azúcares C5 y 60,86% de azúcares C6. Estos polisacáridos se utilizaron con éxito para producir levulinato de metilo mediante la conversión simultánea de ambos tipos de azúcares bajo irradiación microondas en un medio rico en metanol utilizando un catalizador simple y económico como el Al2SO4. En este caso, se obtuvo un rendimiento óptimo de levulinato de metilo del 40% a partir de polisacáridos purificados de residuos de la poda de laurel tras un proceso simple de extracción/purificación de carbohidratos combinado con un paso catalítico asistido por microondas. A pesar de que los polisacáridos vegetales principales de la pared celular son la celulosa y las hemicelulosas, los polisacáridos pécticos pueden representar hasta el 30% de la pared primaria. Estos polisacáridos pécticos han despertado gran interés en los últimos años para su aplicación en áreas como la cosmética, la alimentación, la farmacia y el envasado activo de alimentos. Por ello, la Publicación IV estudia el aislamiento potencial de polisacáridos pécticos a partir de residuos de la poda de laurel y su aplicación como aditivos en películas para envasado activo de alimentos. La obtención de estas pectinas se llevó a cabo mediante extracción secuencial con agua subcrítica, una tecnología novedosa para la extracción de fracciones de polisacáridos con funcionalidades moleculares preservadas, utilizando diferentes combinaciones de tiempo (5, 10, 15 y 20 min) y temperatura (100, 120, 140 y 160 °C). Los polisacáridos extraídos estaban altamente enriquecidos en pectinas conservando su alto peso molecular (10-100 kDa), presentando además propiedades ideales para la citada aplicación. Posteriormente, se prepararon películas de quitosano enriquecidas con las pectinas, las cuales mejoraron las propiedades ópticas (≥95% de capacidad de barrera a la luz-UV), antioxidantes (≥95% de actividad de barrido de radicales) y la permeabilidad al vapor de agua, en comparación con las películas de quitosano puro. Además, la actividad antimicrobiana del quitosano se mantuvo en las películas híbridas. La adición del 10% de pectinas también mejoró las propiedades mecánicas, aumentando el módulo de Young en un 12% y la resistencia a la tensión en un 51%. Así, este trabajo demuestra la aplicación de fracciones ricas en pectinas procedentes de residuos de la poda de laurel para su uso como aditivo en aplicaciones de envasado activo de alimentos, con triple acción como antioxidante, barrera y antimicrobiana. Por último, la Publicación V contenida en la presente Tesis Doctoral trata sobre el fraccionamiento, purificación y aplicación de la celulosa, la fracción polimérica más abundante de los materiales lignocelulósicos. Así, los residuos de la poda de laurel fueron empleados para la producción de micro/nanofibras de celulosa y su aplicación como refuerzo en aerogeles de quitosano aplicables como almohadillas absorbentes para el envasado de alimentos. Las micro/nanofibras fueron obtenidas mediante homogeneización a alta presión, previo pretratamiento químico de oxidación mediada por TEMPO. Se obtuvieron dos clases de micro/nanofibras, con alto y bajo contenido en lignina residual, con el objetivo de estudiar también el efecto de la lignina sobre la aplicación deseada. Posteriormente, se caracterizaron las micro/nanofibras producidas y se prepararon los aerogeles. Como resultado, se obtuvieron aerogeles altamente porosos con propiedades mecánicas mejoradas gracias a la inclusión de las micro/nanofibras en su estructura, especialmente cuando éstas se encontraban presentes al 5%. La ausencia de lignina en las micro/nanofibras condujo a una fuerte auto-asociación aumentando este efecto refuerzo. Una vez encontrada la formulación óptima, se procedió a la fabricación de los aerogeles bioactivos, conteniendo extracto de las hojas de laurel a distintas proporciones. Se observó que la presencia de lignina en las micro/nanofibras fue determinante en los perfiles de liberación del extracto, encontrándose que los aerogeles bioactivos que contenían las micro/nanofibras con lignina liberaban el extracto más rápidamente al medio que los que contenían las micro/nanofibras libres de lignina, alcanzando en ambos casos una capacidad antioxidante máxima. Finalmente, el estudio de los aerogeles bioactivos como almohadillas absorbentes para la conservación de carne, llevado a cabo en muestras de hamburguesas, mostró que estos materiales contribuyen a conservar el alimento durante 10 días como carne fresca cuando se formulan con ≥2% de extracto. Además, la presencia de lignina residual en las fibras contribuyó a este retraso en la oxidación de la carne durante el almacenamiento.Due to the economic and environmental challenges facing society today, the member states of the United Nations proposed the 17 Sustainable Developments Goals (SDGs) in 2015. These goals focus on promoting ways of achieving sustainability in all possible areas (water, energy, climate, industries, economy, science, and technology). In this way, the need for society’s transition to the bioeconomy becomes imminent. Bioeconomy plays an important role in achieving the sustainable development since its main objective is that the current economy becomes based on the use of renewable resources and their conversion into high added-value products. The depletion of fossil resources, as well as fluctuating petroleum prices and environmental pollution problems, call for the search for a new perspective where the use of renewable resources is the basis. In this sense, biorefineries of lignocellulosic materials emerge as a brilliant solution. In biorefinery systems, different types of lignocellulosic residues are valorized to obtain useful, efficient, and valuable products that will help to achieve the much-desired sustainable development. Thus, this Doctoral Thesis has addressed different ways for the valorization of bay tree (Laurus nobilis L.) pruning waste from the biorefinery point of view, through its transformation, fractionation, and application in the preparation of new materials and high added-value products. Chemical modification of lignocellulosic residues by liquefaction reactions has emerged in recent years as a novel technique for the preparation of composite materials, acrylates and polyurethanes based on natural compounds. The polyols commonly used in the polyurethane industry are of petrochemical origin. Therefore, the preparation of natural polyols with similar characteristics to those derived from petroleum could open an alternative and sustainable path in the polyurethanes market. In this sense, Publication I of this Doctoral Thesis describes the synthesis of polyols from bay tree pruning residues, without previous fractionation process, and their application for the preparation of insulating polyurethane foams. The polyol obtained showed similar properties (number of hydroxyl groups, viscosity, and molecular weight) or even better than the polyols currently available on the market, in addition to reporting high liquefaction performance. Therefore, the polyol was perfectly applicable for the preparation of the foams. The insulating foams were prepared considering several parameters that usually influence the final structure of these materials: the type of diisocyanate used (MDI or TDI) and the addition of water as a physical blowing agent. According to the results obtained, the foams prepared with TDI showed an optimum formulation at an NCO/OH (RNCO/OH) molar ratio of 1.1 (40% wt. bay tree pruning polyol and without the addition of the blowing agent) in terms of bulk density and mechanical properties (compressive strength and Young's modulus). In the case of foams prepared with MDI, the optimum formulation was found to be RNCO/OH 0.63 (50% wt. bay tree pruning polyol and with the addition of the blowing agent). All formulated foams had a small and closed cell morphology and a higher thermal stability with the presence of the synthesized polyol. The results obtained in this study have allowed to suggest bay tree pruning waste polyol as a suitable substitute for the petroleum-based polyurethanes. On the other hand, traditionally, the best-known application of bay tree has been through its essential oil in cooking and pharmacy, despite having demonstrated good results in the treatment of diseases thanks to its antioxidant properties. These natural extracts are usually obtained by conventional Soxhlet extraction, which requires large volumes of extraction solvent as well as long extraction times. Going one step further, Publication II focuses on the optimization of obtaining natural extracts from bay leaves by environmentally friendly intensification methodologies. In this sense, a mechanochemical pretreatment protocol was established and applied on the sample to facilitate the subsequent extraction process. This pretreatment was carried out by evaluating the influence of different solid reagents (Na2CO3, BaCO3, Li2CO3, CoCO3, K2CO3 and CaCO3) and was compared with conventional extraction, as well as with other novel techniques in the field of bioactive compound extraction such as ultrasound and microwave irradiation. This study showed that mechanochemical pretreatment allowed obtaining extracts with phenolic contents comparable to those of conventional extraction (75.54 GAE/g extract), with the advantage that, for the same value, the total extraction time was reduced more than 10 times by using mechanochemistry. The main compounds identified in the extract were eugenol, methyleugenol and elemicin. Although ultrasound and microwave-assisted extractions resulted in higher yields and higher values in the properties of the extracts evaluated than those performed with mechanochemical pretreatment, the present study proposes the substitution of conventional extraction by mechanochemistry to obtain the same yield, but in a more sustainable way. The next approach for the valorization of bay tree pruning waste was its fractionation to obtain one of the lignocellulosic fractions present and its subsequent conversion into high value-added compounds. Thus, Publication III deals with the extraction of polysaccharides (hemicelluloses and starch) from bay tree pruning waste and their use as a source of C5 and C6 sugars for the synthesis of methyl levulinate, a high-value added molecule because it is an important platform molecule for the synthesis of relevant chemicals such as γ-valerolactone. The polysaccharide fraction was obtained by hydrothermal extraction (autohydrolysis), determining the optimum conditions by means of an experimental design in which different temperatures (160, 180, 190 and 200 °C) and times (30, 45, 60 and 75 min) were considered. All the fractions obtained were characterized to determine the carbohydrate profile, phenolic acids, proteins, and molecular weight distributions. The polysaccharides obtained under the optimum conditions (160 °C 45 min) were composed of a mixture of 37.87% C5 sugars and 60.86% C6 sugars. These polysaccharides were successfully used to produce methyl levulinate by simultaneous conversion of both types of sugars under microwave irradiation in a methanol-rich medium using a simple and inexpensive catalyst such as Al2SO4. In this case, an optimum methyl levulinate yield of 40% was obtained from polysaccharides purified from bay tree pruning waste after a simple carbohydrate extraction/purification process combined with a microwave-assisted catalytic step. Although the main plant polysaccharides of the cell wall are cellulose and hemicelluloses, pectic polysaccharides can represent up to 30% of the primary wall. These pectic polysaccharides have attracted great interest in recent years for their application in areas such as cosmetics, food, pharmaceuticals, and active food packaging. Therefore, Publication IV studies the potential isolation of pectic polysaccharides from bay tree pruning waste and their application as additives in films for active food packaging. These pectins were obtained by sequential subcritical water extraction, a novel technology for the extraction of polysaccharide fractions with preserved molecular functionalities, using different combinations of time (5, 10, 15 and 20 min) and temperature (100, 120, 140 and 160 °C). The extracted polysaccharides were highly enriched in pectins preserving their high molecular weight (10-100 kDa), also presenting ideal properties for the mentioned application. Subsequently, chitosan films enriched with the pectins were prepared, which improved the optical properties (≥95% light-UV barrier capacity), antioxidant capacity (≥95% radical scavenging activity) and water vapor permeability compared to pure chitosan films. Moreover, the antimicrobial activity of chitosan was maintained in the hybrid films. The addition of 10% pectins also improved the mechanical properties, increasing Young's modulus by 12% and tensile strength by 51%. Thus, this work demonstrates the application of pectin-rich fractions from bay tree pruning waste as an additive in active food packaging applications, with triple action as antioxidant, barrier and antimicrobial. Finally, Publication V contained in this Doctoral Thesis deals with the fractionation, purification, and application of cellulose, the most abundant polymeric fraction of lignocellulosic materials. Thus, bay tree pruning waste was used for the production of cellulose micro/nanofibers and their application as reinforcement in chitosan aerogels applicable as absorbent pads for food packaging. The micro/nanofibers were obtained by high-pressure homogenization, prior TEMPO-mediated oxidation as chemical pretreatment. Two kinds of micro/nanofibers were obtained, with high and low residual lignin content, in order to study also the effect of lignin on the desired application. Subsequently, the produced micro/nanofibers were characterized, and aerogels were prepared. As a result, highly porous aerogels with improved mechanical properties were obtained due to the inclusion of micro/nanofibers in their structure, especially when these were present at 5%. The absence of lignin in the micro/nanofibers led to a strong self-association enhancing this reinforcing effect. Once the optimal formulation was found, the bioactive aerogels were fabricated, containing the bay leaf extract at different proportions. It was observed that the presence of lignin in the micro/nanofibers was determinant in the release profiles of the extract, finding that the bioactive aerogels containing the micro/nanofibers with lignin released the extract more rapidly to the medium than those containing the lignin-free micro/nanofibers, reaching in both cases a maximum antioxidant capacity. Finally, the study of bioactive aerogels as absorbent pads for meat preservation in burger samples showed that these materials contribute to preserve the food for 10 days as fresh meat when formulated with ≥2% extract.
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