No description available.

No description available.

No / In recent years, for neurodegenerative diseases therapy, research has focused on the stem cells therapy. Due to promising findings in stem cell therapy, there are various sources of stem cells for transplantation in human. The aim of this study was to evaluate sciatic nerve regeneration in the rat after nerve transaction followed by human endometrial stem cells (hEnSCs) treatment into poly (e-caprolactone)/collagen/nanobioglass (PCL/collagen/NBG) nanofibrous conduits. After treatment of animals, the performance in motor and sensory tests, showed significant improvement in rats treated with hEnSCs as an autograft. H&E images provided from cross-sectional and, longitudinal-sections of the harvested regenerative nerve as well as immunohistochemistry results indicated that regenerative nerve fibres had been formed and accompanied with new blood vessels in the conduit cell group. Due to the advantage of high surface area for cell attachment, it is reported that this electrospun nerve conduit could find more application in cell therapy for nerve regeneration in future, to further improve the functional regeneration outcome, especially for longer nerve defect restoration. In conclusion, our results suggest that the PCL/collagen/NBG nanofibrous conduit filled with hEnSCs is a suitable strategy to improve nerve regeneration after a nerve transaction in rat. / Iran National Science Foundation (INSF) grant number 95849510

Use of a mixed triisobutylaluminum/1,1-diphenylhexyllithium intiator enabled the anionic polymerization of methyl methacrylate at room temperature, resulting in narrow molecular weight distributions and syndiorich structures. Polymerizations were controlled above Al:Li = 2, and control significantly decreased at elevated temperatures above 25 °C. A significant increase in Tg with increasing control of syndiotacticity demonstrated the ability to tailor polymer properties using this technique. Analysis with MALDI-TOF/TOF spectroscopy revealed the dominance of a back-biting side reaction at elevated temperatures. Hydroxy-functional random and block copolymers of n-butyl acrylate (nBA) and 2-hydroxyethyl acrylate were synthesized using nitroxide mediated polymerization. Controlled polymerization was demonstrated, resulting in narrow polydispersities and linear molecular weight vs. conversion plots. In situ FTIR spectroscopy monitored the polymerizations and revealed pseudo first order rate kinetics for random copolymerizations. Protection of the hydroxyl using trimethylsilyl chloride alleviated isolation issues of amphiphilic polymer products. For the first time zwitterion-containing copolymers were electrospun to form nanoscale fibers with diameters as low as 100 nm. Free radical copolymerization of nBA and sulfobetaine methacrylamide produced zwitterionic copolymers with 6-13 mol % betaine. Dynamic mechanical analysis revealed a rubbery plateau and biphasic morphology similar to ionomers. Electrospinning from chloroform/ethanol solutions (80/20 v/v) at 2-7 wt % afforded polymeric fibers at viscosities below 0.02 Pa™s, which is the lowest viscosity observed for fiber formation in our laboratories. We hypothesized that intermolecular interactions rather than chain entanglements dominated the electrospinning process. Solution rheology of zwitterionic copolymers containing 6 and 9 mol % sulfobetaine methacrylate functionality revealed two concentration regimes with a boundary at ~1.5 – 2.0 wt %, regardless of molecular weight. This transition occurred at an order of magnitude lower specific viscosity than the entanglement concentration (Ce) for poly(nBA), and correlated to the onset of fiber formation in electrospinning. Comparison to existing models for polymer solution dynamics showed closest agreement to Rubinstein's theory for associating polymers, in support of our hypothesis that zwitterionic interactions dominate solution dynamics. The effect of ionic liquid (IL) uptake on mechanical properties and morphology of zwitterionic copolymers was explored using 1-ethyl-3-methylimidazolium ethylsulfate (EMIm ES). Dynamic mechanical analysis and impedance spectroscopy revealed a significant change in properties above a critical uptake of ~10 wt % IL. X-ray scattering revealed a significant swelling of the ionic domains at 15 wt % IL, with a 0.3 nm-1 shift in the ionomer peak to lower scattering vector. Results indicated the water-miscible IL preferentially swelled ionic domains of zwitterionic copolymers. / Ph. D.

As the world population grows, a persistent pressure on natural resources remains. Resource requirements have extensively expanded due to industrialization. Several technological advancements continually aim to alleviate these resource shortages by targeting existing shortcomings in effective and efficient material design. Practical, high-performing, and economical materials are needed in several key application areas, including energy storage, energy harvesting, electronics, catalysis, and water purification. Further development into high-performing and economical materials remain imperative. Innovators must seek to develop technologies that overcome fundamental limitations by designing materials and devices which address resource challenges. Carbon serves as a versatile material for a wide range of applications including purification, separation, and energy storage owing to excellent electrical, physical, and mechanical properties. One-dimensional (1D) carbon fiber in particular is renowned for excellent strength with high surface-to-volume ratio and is widely commercially available. Although an exceptional candidate to address current energy and environmental needs, carbon fibers require further investigation to be used to their full potential. Emerging strategies for carbon fiber design rely on developing facile synthetic routes for controlled carbon structures. The scientific community has shown extensive interest in porous carbon fabrication owing to the excellent performance enhancement in separation, filtration, energy storage, energy conversion, and several other applications. This dissertation both reviews and contributes to the recent works of porous carbon and their applications in energy and environmental sciences. The background section shows recent development in porous carbon and the processing methods under investigation and current synthetic methods for designing porous carbon fibers (PCF). Later sections focus on original research. A controlled radical polymerization method, reversible addition-fragmentation chain transfer (RAFT), enabled a synthetic design for a block copolymer precursor, poly(methyl methacrylate) (PMMA) and polyacrylonitrile (PAN). The block copolymer (PMMA-b-PAN) possesses a unique microphase separation when electrospun and develop narrowly disperse mesopores upon carbonization. The PMMA and PAN domains self-assemble in a kinetically trapped disordered network whereby PMMA decomposes and PAN cross-links into PCF. The initial investigation highlights the block copolymer molecular weight and compositional design control for tuning the physical and electrochemical properties of PCF. Based on this study, mesopore (2 – 50 nm) size can be tuned between 10 – 25 nm while maintaining large surface areas, and the PAN-derived micropores (< 2 nm). The mesopores and micropores both contribute to the development of the unique hierarchical porous carbon structure which brings unprecedented architectural control. The pore control greatly contributes to the carbon field as the nano-scale architecture significantly influences performance and functionality. The next section uses PCF to clean water sources that are often tainted with undesirable ions such as salts and pollutants. Deionization or electrosorption is an electrochemical method for water purification via ion removal. I employed the PCFs as an electrode for deionization because of their high surface area and tunable pore size. Important for deionization, the adsorption isotherms and kinetics highlight the capacity and speed for purification of water. I studied PCF capacitive filtration on charged organic salts. Because PCF have both micropores and mesopores, they were able to adsorb ions at masses exceeding their own weight. The PFC adsorption efficiency was attributed to the diffusion kinetics within the hierarchical porous system and the double layer capacitance development on the PCF surface. In addition, based on the mechanism of adsorption, the PCFs showed high stability and reusability for future adsorption/desorption applications. The PCF performance as an electrosorption material highlights the rational design for efficient electrodes by hierarchical interconnected porosity. Another application of PFCs is updating evaporative desalination methods for water purification. Currently distillation is not widely used as a source of potable water owing to the high cost and energy requirement. Solar desalination could serve as a low-cost method for desalination; however, the evaporation enthalpy of water severely limits practical implementation. Here I apply the pore design of PCF as a method for water nano-confinement. Confinement effects reduce water density and lowers evaporation enthalpy. Desalination in PCF were studied in pores < 2 nm to 22 nm. The PCF pore size of ~ 10 nm was found to be the peak efficiency and resulted in a ~ 46% reduction in enthalpy. Interestingly, the PCF nano-confinement also contributed to the understanding in competing desorption energy for evaporation in micropores. The pore design in PCF also shows confinement effects that can be implemented in other environmental applications. Lastly, the block copolymer microphase morphology was explored in a vapor induced phase separation system. The resulting PCF properties showed a direct influence from the phase separation caused by nonsolvent. At low nonsolvent vapor, a disordered microphase separation occurred, however upon application of nonsolvent vapor, the polymer chains reorganized. The reorganization initially improved mechanical properties by developing more long-range ordered graphic chains in the PAN-derived carbon. However, at higher nonsolvent vapor concentrations, the fibers experienced polymer precipitation which resulted in bead and clump formation in the fiber mats. The beads and clumps lowered both mechanical properties and electrochemical performance. The vapor induced phase separation showed a method for enhancing mechanical properties without compromising electrochemical performance in flexible carbon fibers. / Doctor of Philosophy / Nanomaterials possess mechanical, physical, and electrical properties to address important growing demands for precious resources such as clean water and energy. Many advancements in nanomaterials focus on improving fine-tune architectures which facilitate efficiency in composites, filtration systems, catalytic systems, energy storage devices, and electronics. Carbon material has remained a valuable candidate in these fields owing to its abundancy economical cost, and excellent properties. Several carbon forms provide unique characteristics including 0D dots, 1D fibers, 2D sheets, and 3D monoliths. Of these, 1D fibers possess excellent strength, resiliency, and conductivity and have been commercially employed in modern automotive, airplanes, membranes, and conductors. However, traditional carbon fiber fabrication does not match the growing needs in performance. Therefore, in this dissertation I explore the design and processing of carbon fibers for controlled architectures. These designs were then systematically studied in filtration systems, solar desalination, and flexible electronics. Block copolymers provide a new way to combine polymers for drastically new materials and effects. Firstly, I conducted a comprehensive study on the synthesis and composition of this block copolymer which laid the foundation for future carbon fiber design. The polymer consists of two chains – one chain to develop carbon structures upon heating; the second which decomposes into pores upon heating. Therefore, with these two chains, a highly porous carbon fiber can be created. The reaction I studied could mostly be controlled with time to change the length of each chain. Ultimately, the pore size and surface area depend on the relative lengths of each chain. Future studies, including ones in this work, could therefore tune pore size and surface area for many applications. Carbon fibers with graphitic structure are inherently conductive and thereby attract charged molecules in a solution. Diffusion and capacity serve as major factors in these types of systems. With the aforementioned control of the carbon fibers a diffusion study was conducted with charged pollution ions. Owing to the conductive nature, a voltage supply was attached to the fibers, which would adsorb ions electrostatically, termed "electrosorption". The electrosorption performance within the carbon fibers elucidated the interconnected porous structure and how ions orientate themselves along the surface of the fibers. In addition, with the development of ion orientation along the surface of the fibers, a greater than 1:1 ratio of carbon weight to ion weight adsorbed developed owing to the diffusion and ion stacking capabilities. Additionally, the study provides deeper investigation into movement of ions within confined nano-porous material. The ever-growing need for renewable resources such as fresh water has pressured development into more efficient material. Solar desalination has attractive qualities which makes it a focus for micro-scale studies. One of the major limitations lies in the high energy input change liquid water into vapor. At 100 °C for boiling, desalination lacks sufficient efficiency for large-scale applications in evaporation. However, by utilizing nano-scale material, the fundamental properties of water can be altered. The carbon fibers were then created with various nano-pore sizes which revealed nano-confinement effects when subject to solar heating. With the shrinking of pore sizes, the density of water also decreased. A lower density means less energy was required to convert water from a liquid to a vapor state. The carbon fibers helped reveal real applications into confinement effects on water based on pore size. Apart from just desalination, this means future environmental application can utilize this knowledge for more effective and smart designs. The carbon fibers outstanding electrical and mechanical properties have spurred research and development since the mid-1900s. Since then, carbon fiber technologies have grown from facile and efficient productions means, to high end, high performance smart design. The work presented here furthers two major components: first, the high-performance design of porous carbon fiber; second, the fundamental principles in nano-material properties and their applications. By first constructing a design of polymer synthesis and then subsequent studies, development of nano-porous carbon energy progresses knowledge on smart and efficient designs. These materials provide a platform for future energy and environmental sciences.

Partial or complete tears of the anterior cruciate ligament (ACL) can greatly afflict quality of life and often require surgical reconstruction with autograft or allograft tissue to restore native knee biomechanical function. However, limitations exist with these treatments that include donor site pain and weakness found with autografts, and longer "ligamentization" and integration times due to the devitalization of allograft tissue. Alternatively, a tissue engineering approach has been proposed for the fabrication of patient-specific grafts that can more rapidly and completely heal after ACL reconstruction. Electrospun micro-fiber networks have been widely utilized as biomaterial scaffolds to support the growth and differentiation of mesenchymal stem cells toward many tissue lineages including ligament. However, these micro-fiber networks do not possess suitable sizes and shapes for a ligament application and cannot support cell infiltration. The objective of this work was to develop techniques to 1) rapidly cellularize micro-fiber networks, 2) assemble micro-fiber networks into cylindrical composites, 3) provide cues to mesenchymal stem cells (MSCs) to guide their differentiation toward a ligament phenotype. The cellularization of micro-fiber networks was performed utilizing a co-electrospinning/electrospraying technique. Cells deposited within a cell culture medium solution remained where they were deposited and did not proliferate. The inclusion of space-filling hydrogel network such as collagen was necessary to reduce the density of the micro-fiber network to facilitate spreading. However, it became apparent that the incorporation of significant collagen phase was necessary for long-term MSC survival within the micro-fiber network. Next, two approaches were developed to fabricate large cylindrical, composites. The first approach utilized a co-electrospinning/electrospraying technique to generate micro-fiber/collagen composites that were subsequently rolled into cylinders. These cylindrical composites exhibited greater diameters and water weight percentages as collagen content increased. However, the high micro-fiber content of these composites was inhibitory to cell survival. In the second approach, thin layers (~5-10 fibers) of aligned electrospun PEUR fibers were encapsulated within a collagen gel and subsequently rolled the composites into cylinders. These sparse-fiber composites were nearly 98% by weight water and confocal imaging revealed the presence of sparse fiber layers (~5 fibers thick) separated by approximately 200 μm thick collagen layers. We hypothesize that the proliferation and migration of MSCs within these micro-fiber/collagen composites may not be restricted by the presence of a dense, non-manipulatable electrospun fiber network present in traditionally rolled fiber composites. Simple model platforms were then developed to study the influence of sparse micro-fibers on MSCs differentiation within a collagen hydrogel. MSCs in the presence of the softest (5.6 MPa) micro-fibers elongated and oriented to the underlying network and exhibited greater expression of scleraxis, and α-smooth muscle actin compared to the stiffest (31 MPa) fibers. Additionally, preliminary results revealed that the incorporation of fibroblast growth factor-2 and growth and differentiation factor-5 onto micro-fibers through chemical conjugation enhanced expression of the ligamentous markers collagen I, scleraxis, and tenomodulin. In conclusion, micro-fiber/collagen composite materials must possess sufficient space to support the infiltration and differentiation of MSCs. The strategies described in this document could be combined to fabricate large, micro-fiber/collagen composites that can support cell infiltration and provide relevant cues to guide the formation of an engineered ligament tissue. / Ph. D.

Grafts currently used for the repair of anterior cruciate ligament (ACL) ruptures integrate poorly with bone due to a significant mismatch in properties between graft and bone. Specifically, conventional grafts (e.g., hamstring tendon) are unable to recapitulate intricate gradients in mechano-chemical properties and extracellular matrix (ECM) architecture found at natural bone-ligament (B-L) transitions, and thus result in stress-concentrations at the graft-bone interface leading to graft failure. In contrast, tissue-engineered scaffolds possessing gradients in properties can potentially guide the establishment of phenotypic gradients in bone marrow stromal cells (BMSCs), and thus aid the regeneration of B-L transitions in the long-term. Towards the eventual goal of regenerating complex tissue transitions, this project employs three complementary strategies to fabricate graded scaffolds. The three strategies involve the presentation of gradients in 1) mineral content, 2) scaffold architecture and 3) growth factor (GF) concentration within scaffolds to control BMSC morphology and phenotype. The first strategy involved co-electrospinning two polymers (one doped with hydroxyapatite) from offset spinnerets onto a rotating drum to produce scaffolds possessing a gradient in mineral content. Post-electrospinning, these graded scaffolds were treated with a simulated body fluid to further enhance the gradient. Analysis of mRNA expression of osteoblastic makers by BMSCs and the deposition of bone-specific ECM proteins indicated that the scaffolds could guide the formation of an osteoblastic phenotypic gradient. The second strategy involved electrospinning two polymer solutions onto a custom-designed dual-drum collector to fabricate scaffolds possessing region-wise differences in fiber alignment, diameter and chemistry. Specifically, electrospinning onto the dual-drum collector resulted in the deposition of aligned fibers from one polymer solution in the gap region between the drums, randomly oriented fibers from the other polymer solution on one of the drums and a mixture of fibers from both polymer solutions in the overlap region in between. The topographical cues within these scaffolds were shown to result in region-dependent BMSC morphology and orientation. Although the long-term goal of the third strategy was to create a co-electrospun scaffold possessing a gradient in GF concentration, a new technique to protect GF activity within electrospun scaffolds via the use of gelatin microspheres was first validated. Preliminary results from these studies indicate that microspheres can protect and deliver a model protein (lysozyme) in active conformation from electrospun scaffolds. These results further suggest that gradients of GF concentration can be achieved in the long-term by protecting GFs within microspheres and co-electrospinning as described in the first strategy. In conclusion, the results from this project suggest that graded scaffolds can help guide the formation of gradients in cell morphology, orientation and phenotype, and thus potentially promote the regeneration of B-L transitions in the long-term. The three strategies described in this project can be employed in concert to create scaffolds intended for the regeneration of complex tissue transitions. / Ph. D.

Rupture of the anterior cruciate ligament (ACL) is one of the most common ligamentous injuries of the knee. Post rupture, the ACL does not heal on itself due to poor vasculature and hence surgical intervention is required to treat the ACL. Current surgical management of ACL rupture consists of reconstruction with autografts or allografts. However, the limitations associated with these grafts have prompted interest in tissue engineered solutions that combine cells, scaffolds and stimuli to facilitate ACL regeneration. This thesis describes a ligament tissue engineering strategy that involves incorporating biomolecules within fibers-based electrospun meshes which mimics the extra-cellular matrix microarchitecture of ligament. However, challenges exist with incorporation of biomolecules. Therefore, the goal of this research project was to develop two techniques to incorporate biomolecules within electrospun meshes: (1) co-axially electrospinning fibers that support surface-grafting of biomolecules, and (2) co-axially electrospinning fibers decorated with biomolecule-loaded microspheres. In the first approach, chitosan was co-axially electrospun on the shell side of poly caprolactone (PCL) and arginine-glycine-aspartate (RGD) was attached to the electrospun meshes. Bone marrow stromal cells (BMSCs) attached, spread and proliferated on these meshes. In the second approach, fluorescein isothiocyanate labelled bovine serum albumin (FITC-BSA) loaded chitosan-alginate (CS-AL) microspheres were fabricated. The effects of cation to alginate ratio, type of alginate and concentration of CaCl2 on microsphere size, FITC-BSA loading and release were systematically evaluated. The CS-AL microspheres were then incorporated into the sheath phase of co-axially electrospun meshes to achieve microsphere-decorated fiber composite meshes. The results from these model study suggest that both approaches are tractable for incorporating biomolecules within fibers-based electrospun meshes. Both these approaches provide platform for future studies that can focus on ligament-relevant biomolecules such as FGF-2 and GDF-5. / Master of Science

Among the most common knee ligament injuries are those to the anterior cruciate ligament (ACL). Annually, approximately 350,000 people require surgical ACL reconstruction, accounting for more than $6 billion of health-care costs in the United States alone. An injured ACL loses its functions as it cannot heal with larger injuries and heals slowly with smaller ones. This may introduce complications, such as abnormal joint kinematics and deterioration, prior to complete rupture. Although the use of an autologous graft is the current gold standard for ACL reconstruction surgery, it is associated with donor site morbidity and a decrease in mechanical strength at the donor site. The use of allogenic grafts instead of autografts introduces the risk of disease transmission. Furthermore, integration of soft tissue grafts (e.g., hamstring tendon) to native bone is slow and risks graft pullout. To circumvent these limitations, tissue engineering seeks to fabricate suitable biomaterials that could replace the entire ACL, stimulate regeneration of the ligament tissue, and integrate with host bone tissue. Numerous efforts have led to the development of complex, multi-phased biomaterial scaffold designs that are intended to deliver an array of cell types and biological cues. Particularly, scaffolds that possess bone-regenerating biomaterials at the ends are envisioned to facilitate rapid integration with the femur and tibia. Electrospun fiber scaffolds continue to be regularly utilized for their high tensile strength, flexibility, and ability to bend. Nevertheless, fibrous scaffolds are inert and require the incorporation of trophic factors to guide tissue regeneration. Additionally, electrospun fibers are often densely packed, which can hinder cell infiltration and subsequent tissue formation. The objective of this work was to guide bone remodeling through the incorporation of trophic factors with 1) electrospun fiber scaffolds or 2) nanoparticles that could be combined with electrospun fiber scaffolds, and 3) to develop model three-dimensional fiber-hydrogel composites that support cell viability and proliferation. Two approaches were utilized to present the trophic factor bone morphogenic protein (BMP)-2 to stimulate bone formation. In the first approach, electrospun fibers were modified through the adsorption or covalent conjugation of BMP-2. These fibers exhibited increased BMP-2 concentrations with covalent conjugation over adsorption, and the incorporation of heparin into the fibers improved both adsorption and conjugation. Mesenchymal stem cells (MSCs) – that have the capacity to differentiate into osteoblastic cells – were able to attach and proliferate on all films yet appeared to do so to a greater extent on surfaces with higher heparin contents. Additionally, markers of osteoblastic differentiation were significantly higher on surfaces with covalently conjugated BMP-2 than on those with adsorbed BMP-2. In the second approach, a nanoparticle system was produced to control BMP-2 delivery and release. Importantly, this flexible system can be fabricated separately, and then combined with a scaffold for tissue regeneration. In this approach, BMP-2 was combined with chitosan nanoparticles through adsorption, encapsulation, or covalent conjugation. The particular BMP-2 incorporation technique had no significant effect on BMP-2 incorporation efficiencies, but affected particle size and BMP-2 release kinetics. Specifically, covalent conjugation method caused the aggregation of particles while adsorption method allowed the most sustainable release. MSCs cultured in the presence of the different particles survived and proliferated, but only particles with adsorbed BMP-2 stimulated osteoblastic differentiation. Finally, three-dimensional fiber-hydrogel composites of various models were fabricated to mimic the complexity of full-sized scaffolds for ACL regeneration, and to study cell infiltration, differentiation, and tissue formation. A collagen hydrogel phase was introduced to electrospun fiber scaffolds using different approaches. MSCs seeded within a thin collagen layer were able to proliferate, sense underlying substrate and spread according to fiber orientation, while those within thicker layers were not. Additionally, cells initially present in only the collagen phase infiltrated to the fiber phase. These results demonstrate that minor changes in fabrication steps to combine the two phases could significantly alter cell function during the formation of three-dimensional fiber-hydrogel composites for tissue regeneration. / Doctor of Philosophy / The anterior cruciate ligament (ACL) is one of four ligaments that connect the thigh bone to the shin bone and stabilize the knee. Injuries to the ACL often occur during high impact sports, and ruptures can necessitate surgical intervention. ACL reconstruction surgery involves drilling tunnels through the ends of leg bones, deploying the tissue graft through the knee joint and bone tunnels, and anchoring it within the bone tunnels. The most common grafts are autografts that use tendons of the patient's own body or allografts that are obtained from cadavers. The complications associated with autografts include pain at the site of tissue harvest, while allografts risk disease transmission. Additionally, directly affixing a soft tissue graft (e.g., the hamstring tendon) to bone within the bone tunnel suffers from slow tissue integration and risk of pull-out. Tissue engineering is a field that seeks to develop devices to direct the regeneration of damaged tissues and organs. In the context of ACL repair, it seeks to achieve a biomaterial device with the properties of ACL, that can both guide the regeneration of ligament tissue and facilitate integration with bone tunnels, eliminating the need for autografts and allografts and their associated risks. Toward the development of an engineered ACL, this work focuses on improving graft-to-bone integration. In the first project, fibrous materials are surface-modified with bone morphogenetic protein (BMP)-2 (a bone-forming protein), and then tested for their ability to stimulate formation of a bone-like tissue in cell culture. In the second project, the deployment of BMP-2 either on the surface of or within nanoparticle delivery vehicles is evaluated as an alternative strategy to stimulate bone-like tissue formation. The third project explores the inclusion of a hydrogel phase to facilitate cell infiltration and bone-like tissue formation within fibrous materials. Together these studies provide insights into how the architecture of the engineered tissue and the deployment of bone-forming proteins can be used to enhance ACL regeneration.

Tesis por compendio / [ES] El uso masivo de plásticos sintéticos y su impacto medioambiental obliga a buscar alternativas biodegradables para el envasado de los alimentos,etapa necesaria para su adecuada conservación.Así mismo,la necesidad de incrementar la vida útil de los alimentos ha despertado gran interés en el desarrollo de materiales activos(antimicrobianos y antioxidantes)que mantengan su calidad y seguridad por más tiempo,mediante el uso de compuestos de origen natural,seguros para el consumidor.En este sentido,el desarrollo de materiales biodegradables activos para el envasado de alimentos constituye hoy en día un reto importante para la industria alimentaria.En la presente Tesis Doctoral,se ha estudiado la encapsulación de carvacrol mediante el electroestirado o extensión y secado de diferentes disoluciones poliméricas con carvacrol.Se han utilizado polímeros biodegradables portadores de diferente polaridad(almidón termoplástico:TPS,polivinil-alcohol:PVA, policaprolactona:PCL o ácido poliláctico:PLA)disueltos en el solvente adecuado,con el fin de obtener capas activas.Estas capas se han combinado con otras de polímeros con propiedades complementarias,para obtener laminados activos adecuados para el envasado de alimentos.Los laminados combinaron polímeros polares(TPS o PVA)y poliésteres no polares(PCL o PLA)incorporando el carvacrol en una de las capas.Se evaluó la cinética de liberación del activo,así como la acción antimicrobiana de los materiales obtenidos.Los laminados se caracterizaron en su funcionalidad como material de envase(prop. de barrera,mecánicas u ópticas)así como en su estructura y comportamiento térmico.Los estudios de encapsulación revelaron un mayor potencial encapsulante del carvacrol para los polímeros no polares(PCL;PLA),aunque el PVA mostró también una buena afinidad con el compuesto activo.La matriz de PVA mostró una mayor retención de carvacrol mediante electroestirado de sus disoluciones acuosas que por extensión y secado,sin necesidad de adición de tensoactivos como el Tween85.Para la encapsulación en PLA,se usaron mezclas binarias de solventes aptos para contacto con los alimentos(acetato de etilo y DMSO).En este caso,se obtuvo una mayor eficiencia encapsulante del PLA en los materiales obtenidos por extensión y secado que en los electroestirados.La cinética de liberación del carvacrol de las fibras de PCL explicó el mayor efecto antibacteriano contra E.coli,y el escaso efecto antilisteria.La velocidad de liberación del activo aumentó cuando disminuyó la polaridad de los simulantes alimentarios, mostrando una liberación completa en los sistemas apolares,pero solo hasta 75% en los sistemas acuosos,que requerirían una mayor proporción del activo en el envase para potenciar su efectividad.La combinación de láminas de TPS con fibras de PCL cargadas con carvacrol dio lugar a materiales con una permeabilidad al vapor de agua mejorada,en comparación con los films de almidón,sin efectos relevantes sobre las otras propiedades funcionales estudiadas.Cuando los laminados se probaron in vitro contra cepas G(+) y G(-) mostraron un efecto antibacteriano similar al de las fibras de PCL con carvacrol,pero retrasado en el tiempo.Los estudios de desintegración-biodegradación de los laminados almidón-PCL revelaron que las películas con carvacrol afectaron la actividad del inóculo del compost,disminuyendo ligeramente la biodegradabilidad de las películas,pero alcanzando valores de desintegración similares(75-80%)a las muestras libres de carvacrol.Se obtuvieron también laminados de PLA y PVA mediante la extensión y secado de disoluciones acuosas de PVA con carvacrol.La superficie del PLA fue sometida a aminolización a fin de mejorar la extensibilidad de las disoluciones acuosas.A pesar del incremento de la componente polar de la energía superficial del PLA y su mejorada humectabilidad con las soluciones de PVA,estas bicapas no mostraron una mejora significativa en las propied / [CA] L'ús massiu de plàstics sintètics i el seu impacte mediambiental obliga a buscar alternatives biodegradables per a l'envasament dels aliments necessari per a la seua conservació.Així mateix,la necessitat d'incrementar la vida útil dels aliments ha despertat gran interés en el desenvolupament de materials actius(antimicrobians i antioxidants)que mantinguen la seua qualitat i seguretat per més temps,per mitjà de l'ús de compostos d'origen natural,segurs per al consumidor.En este sentit,el desenvolupament de materials biodegradables actius per a l'envasament d'aliments constituïx un repte important per a la indústria alimentària.En la present Tesi Doctoral,s'ha estudiat l'encapsulació de carvacrol per mitjà de l'electroestirat o extensió i assecat de diferents dissolucions polimèriques amb carvacrol.S'han utilitzat polímers biodegradables portadors de diferent polaritat(midó termoplàstic:TPS, polivinil-alcohol:PVA, policaprolactona:PCL o àcid poliláctic:PLA)dissolts en el solvent adequat,a fi d'obtindre capes actives.Estes s'han combinat amb altres de polímers amb propietats complementàries,per a obtindre laminats actius adequats per a l'envasament d'aliments.Els laminats van combinar polímers polars(TPS o PVA)i poliésters no polars(PCL o PLA)incorporant el carvacrol en una de les capes.Es va avaluar la cinètica d'alliberament de l'actiu,així com l'acció antimicrobiana dels materials obtinguts.Els laminats es van caracteritzar en la seua funcionalitat com a material d'envàs(propietats de barrera, mecàniques o òptiques),així com en la seua estructura i comportament tèrmic.Els estudis d'encapsulació van revelar un major potencial encapsulant del carvacrol per als polímers no polars(PCL i PLA),encara que el PVA va mostrar també una bona afinitat amb el compost actiu.La matriu de PVA va mostrar una major retenció de carvacrol per mitjà d'electroestirat de les seues dissolucions aquoses que per extensió i assecat,sense necessitat d'addició de tensioactius com el Tween 85.Per a l'encapsulació en PLA,es van usar mescles binàries de solvents aptes per a contacte amb els aliments(acetat d'etil i DMSO).Es va obtindre una major eficiència encapsulant del PLA en els materials obtinguts per extensió i assecat que en els electroestirats.La cinètica d'alliberament del carvacrol de les fibres de PCL va explicar el major efecte antibacterià contra Escherichia coli,i l'escàs efecte antilisteria.La velocitat d'alliberament de l'actiu va augmentar quan va disminuir la polaritat dels simulants alimentaris,mostrant un alliberament complet en els sistemes no polars, però només fins a un 75% en els sistemes aquosos,que requeririen una major proporció de l'actiu en l'envàs per a potenciar la seua efectivitat.La combinació de làmines de TPS amb fibres de PCL carregades amb carvacrol va donar lloc a materials amb una permeabilitat al vapor d'aigua millorada,en comparació amb els films de midó, sense efectes rellevants sobre les altres propietats funcionals.Quan els laminats es van provar in vitro contra ceps Gram(+) i Gram(-) van mostrar un efecte antibacterià semblant al de les fibres de PCL amb carvacrol,però retardat en el temps.Els estudis de desintegració-biodegradació dels laminats midó-PCL van revelar que les pel·lícules amb carvacrol van afectar l'activitat de l'inocule del compost,disminuint lleugerament la biodegradabilitat,però aconseguint valors de desintegració semblants(75-80%)a les mostres lliures de carvacrol.Es van obtindre també laminats de PLA i PVA per mitjà de l'extensió i assecat de dissolucions aquoses de PVA amb carvacrol.La superfície del PLA va ser sotmesa a aminolizatció a fi de millorar l'extensibilitat de les dissolucions aquoses.A pesar de l'increment de la component polar de l'energia superficial del PLA i la seua millorada mullabilitat amb les solucions de PVA,estes bicapes no van mostrar una millora significativa en les propietats mecàniques i de barrera / [EN] The massive use of synthetic plastics and their environmental impact makes necessary the search for biodegradable alternatives for food packaging. Likewise, the need to increase the shelf life of food has aroused great interest in the development of active materials (antimicrobial and antioxidant) that maintain food quality and safety for longer periods of time through the use of compounds of natural origin, safe for the consumer. In this sense, the development of active biodegradable materials for food packaging is both a major imperative and challenge for the food industry today. In the present Doctoral Thesis, the encapsulation of carvacrol has been studied by means of the electrospinning or casting of different polymeric solutions with carvacrol. Biodegradable polymers with different polarities (thermoplastic starch: TPS, poly(vinyl-alcohol): PVA, poly-(¿-caprolactone): PCL or poly(lactic acid): PLA) dissolved in the appropriate solvent have been used to obtain active layers. These have been combined with other polymers with complementary properties, to obtain active laminates suitable for food packaging. The laminates combined polar polymers (TPS or PVA) and non-polar polyesters (PCL or PLA) incorporating carvacrol in one of the layers. The release kinetics of the active ingredient was evaluated, as well as the antimicrobial action of the materials obtained. The laminates were characterized in their functionality as a packaging material (barrier, mechanical or optical properties), as well as in their structure and thermal behaviour. Encapsulation studies revealed a higher encapsulating potential of carvacrol for non-polar polymers (PCL and PLA), although PVA also showed a good affinity with the active compound. The PVA matrix showed a higher retention of carvacrol by electrospinning of its aqueous solutions than by casting, without the need for addition of surfactants such as Tween 85. For the encapsulation in PLA, binary mixtures of solvents suitable for food contact (ethyl acetate and DMSO) were used. A higher encapsulation efficiency of PLA was obtained in the materials produced by casting than by electrospinning. The carvacrol release kinetics of PCL fibres explained the higher antibacterial effect against Escherichia coli and the lower antilisterial effect. The release ratio of the active ingredient increased when the polarity of the food simulants decreased, showing a complete release in non-polar systems and only up to 75% in aqueous systems that would require a higher proportion of the active ingredient in the packaging material to enhance its effectiveness. The combination of TPS films with carvacrol loaded PCL fibres resulted in materials with improved water vapour permeabilities, compared to starch films, with no relevant effects on the other functional properties. When the laminates were tested in vitro against Gram (+) and Gram (-) strains, they showed a similar antibacterial effect to that of PCL fibres with carvacrol, but delayed in time. Disintegration-biodegradation studies of PCL-starch laminates revealed that carvacrol films affected the activity of the compost inoculum, slightly decreasing the biodegradability of the laminates, but reaching similar disintegration values (75-80%) to the carvacrol-free samples. PLA and PVA laminates were also obtained by casting aqueous PVA solutions with carvacrol. The surface of PLA was submitted to aminolization in order to improve the extensibility of the aqueous solutions. Despite the increase in the polar component of the PLA surface energy and its improved wettability with PVA solutions, these bilayers did not show significant improvement in mechanical and barrier properties over the PLA monolayers. / The authors would like to thank the Ministerio de Economia y Competitividad of Spain, for funding this study as part of projects AGL2013-42989-R and AGL2016-76699-R and predoctoral research grant # BES-2014-068100. / Tampau, A. (2020). Carvacrol encapsulation by electrospinning or solvent casting to obtain biodegradable multilayer active films for food packaging applications [Tesis doctoral]. Universitat Politècnica de València. https://doi.org/10.4995/Thesis/10251/140313 / Compendio