Chitosan-based hydrogels obtained via photoinitiated click polymer IPN reaction

Chitosan (CTS) is a polysaccharide with a wide variety of applications in the biomedical field, owing to its outstanding disinfectant properties, biocompatibility and biodegradability, but with limited mechanical properties. The proposed strategy to improve CTS-based hydrogel properties in this study is the formation of a semi-interpenetrating polymer network (semi-IPN). In this way, a photo-initiated radical click reaction was proposed to obtain a synthetic polymer, whose components were included in a CTS solution, resulting in the semi-IPN network after UV illumination. Different crosslinking degrees (CD) and CTS/polymer ratios were evaluated through rheological characterization, along with an assessment of both variables based on an experimental model design, obtaining that, for every CTS/polymer ratio, intermediate values of CD (8 %) offered the best rheological properties. In addition, chemical and microstructural characterization were carried out for selected hydrogels, obtaining consistent results according to rheological characterization, as the 1/1 CTS/polymer ratio with CD 8 % hydrogel displayed the most homogeneous pore size and distribution, consequently leading to the best rheological performance.This study was financially supported by MCIN/AEI/10.13039/5 01100011033/FEDER, UE, through the project PID2021- 124294OB-C21. The authors gratefully acknowledge their financial support. This work was also possible thanks to the postdoctoral contract of Víctor M. Pérez Puyana from the ‘‘Contratación de Personal Investigador Doctor” supported by the European Social Fund and Junta de Andalucía (PAIDI DOCTOR – Convocatoria 2019–2020, DOC_00586)

Incorporation of ZnO Nanoparticles into Soy Protein-Based Bioplastics to Improve Their Functional Properties

The union of nanoscience (nanofertilization) with controlled release bioplastic systems could be a key factor for the improvement of fertilization in horticulture, avoiding excessive contamination and reducing the price of the products found in the current market. In this context, the objective of this work was to incorporate ZnO nanoparticles in soy protein-based bioplastic processed using injection moulding. Thus, the concentration of ZnO nanoparticles (0 wt%, 1.0 wt%, 2.0 wt%, 4.5 wt%) and mould temperature (70 °C, 90 °C and 110 °C) were evaluated through a mechanical (flexural and tensile properties), morphological (microstructure and nanoparticle distribution) and functional (water uptake capacity, micronutrient release and biodegradability) characterization. The results indicate that these parameters play an important role in the final characteristics of the bioplastics, being able to modify them. Ultimately, this study increases the versatility and functionality of the use of bioplastics and nanofertilization in horticulture, helping to prevent the greatest environmental impact caused.Ministerio de Ciencia e Innovación of the Spanish Government and FEDER (UE), grant number RTI2018-097100-B-C2

Majorana-like Zero Modes in Kekule Distorted Sonic Lattices

[EN] Topological phases have recently been realized in bosonic systems. The associated boundary modes between regions of distinct topology have been used to demonstrate robust waveguiding, protected from defects by the topology of the surrounding bulk. A related type of topologically protected state that is not propagating but is bound to a defect has not been demonstrated to date in a bosonic setting. Here we demonstrate numerically and experimentally that an acoustic mode can be topologically bound to a vortex fabricated in a two-dimensional, Kekul¿e-distorted triangular acoustic lattice. Such lattice realizes an acoustic analog of the Jackiw-Rossi mechanism that topologically binds a bound state in a p-wave superconductor vortex. The acoustic bound state is thus a bosonic analog of a Majorana bound state, where the two valleys replace particle and hole components. We numerically show that it is topologically protected against arbitrary symmetry-preserving local perturbations, and remains pinned to the Dirac frequency of the unperturbed lattice regardless of parameter variations. We demonstrate our prediction experimentally by 3D printing the vortex pattern in a plastic matrix and measuring the spectrum of the acoustic response of the device. Despite viscothermal losses, the measured topological resonance remains robust, with its frequency closely matching our simulations.J. C. acknowledges support from the European Research Council (ERC) through the Starting Grant No. 714577 PHONOMETA and from the MINECO through a Ramon y Cajal grant (No. RYC-2015-17156). J. S.-D. acknowledges support from the Ministerio de Economia y Competitividad of the Spanish Government and the European Union "Fondo Europeo de Desarrollo Regional (FEDER)" through Project No. TEC2014-53088-C3-1-R. P. S.-J. acknowledges support from MINECO/FEDER under Grant No. FIS2015-65706-P. D. T. acknowledges financial support through the Ramon y Cajal fellowship under Grant No. RYC-2016-21188 and to the Ministry of Science, Innovation and Universities through Project No. RTI2018-093921-A-C42.Gao, P.; Torrent Martí, D.; Cervera Moreno, FS.; San-Jose, P.; Sánchez-Dehesa Moreno-Cid, J.; Christensen, J. (2019). Majorana-like Zero Modes in Kekule Distorted Sonic Lattices. Physical Review Letters. 123(19):196601-1-196601-4. https://doi.org/10.1103/PhysRevLett.123.196601S196601-1196601-412319Hasan, M. Z., & Kane, C. L. (2010). Colloquium: Topological insulators. Reviews of Modern Physics, 82(4), 3045-3067. doi:10.1103/revmodphys.82.3045Elliott, S. R., & Franz, M. (2015). Colloquium: Majorana fermions in nuclear, particle, and solid-state physics. Reviews of Modern Physics, 87(1), 137-163. doi:10.1103/revmodphys.87.137Acín, A., Bloch, I., Buhrman, H., Calarco, T., Eichler, C., Eisert, J., … Wilhelm, F. K. (2018). The quantum technologies roadmap: a European community view. New Journal of Physics, 20(8), 080201. doi:10.1088/1367-2630/aad1eaAlicea, J. (2012). New directions in the pursuit of Majorana fermions in solid state systems. Reports on Progress in Physics, 75(7), 076501. doi:10.1088/0034-4885/75/7/076501Nayak, C., Simon, S. H., Stern, A., Freedman, M., & Das Sarma, S. (2008). Non-Abelian anyons and topological quantum computation. Reviews of Modern Physics, 80(3), 1083-1159. doi:10.1103/revmodphys.80.1083Kushwaha, M. S., Halevi, P., Dobrzynski, L., & Djafari-Rouhani, B. (1993). Acoustic band structure of periodic elastic composites. Physical Review Letters, 71(13), 2022-2025. doi:10.1103/physrevlett.71.2022Martínez-Sala, R., Sancho, J., Sánchez, J. V., Gómez, V., Llinares, J., & Meseguer, F. (1995). Sound attenuation by sculpture. Nature, 378(6554), 241-241. doi:10.1038/378241a0Yang, Z., Gao, F., Shi, X., Lin, X., Gao, Z., Chong, Y., & Zhang, B. (2015). Topological Acoustics. Physical Review Letters, 114(11). doi:10.1103/physrevlett.114.114301He, C., Ni, X., Ge, H., Sun, X.-C., Chen, Y.-B., Lu, M.-H., … Chen, Y.-F. (2016). Acoustic topological insulator and robust one-way sound transport. Nature Physics, 12(12), 1124-1129. doi:10.1038/nphys3867Lu, J., Qiu, C., Ye, L., Fan, X., Ke, M., Zhang, F., & Liu, Z. (2016). Observation of topological valley transport of sound in sonic crystals. Nature Physics, 13(4), 369-374. doi:10.1038/nphys3999Deng, Y., Ge, H., Tian, Y., Lu, M., & Jing, Y. (2017). Observation of zone folding induced acoustic topological insulators and the role of spin-mixing defects. Physical Review B, 96(18). doi:10.1103/physrevb.96.184305Wang, M., Ye, L., Christensen, J., & Liu, Z. (2018). Valley Physics in Non-Hermitian Artificial Acoustic Boron Nitride. Physical Review Letters, 120(24). doi:10.1103/physrevlett.120.246601Zhang, Z., Tian, Y., Cheng, Y., Wei, Q., Liu, X., & Christensen, J. (2018). Topological Acoustic Delay Line. Physical Review Applied, 9(3). doi:10.1103/physrevapplied.9.034032Zhang, X., Xiao, M., Cheng, Y., Lu, M.-H., & Christensen, J. (2018). Topological sound. Communications Physics, 1(1). doi:10.1038/s42005-018-0094-4Jackiw, R., & Rossi, P. (1981). Zero modes of the vortex-fermion system. Nuclear Physics B, 190(4), 681-691. doi:10.1016/0550-3213(81)90044-4Shore, J. D., Huang, M., Dorsey, A. T., & Sethna, J. P. (1989). Density of states in a vortex core and the zero-bias tunneling peak. Physical Review Letters, 62(26), 3089-3092. doi:10.1103/physrevlett.62.3089Gygi, F., & Schluter, M. (1990). Electronic tunneling into an isolated vortex in a clean type-II superconductor. Physical Review B, 41(1), 822-825. doi:10.1103/physrevb.41.822Torrent, D., & Sánchez-Dehesa, J. (2012). Acoustic Analogue of Graphene: Observation of Dirac Cones in Acoustic Surface Waves. Physical Review Letters, 108(17). doi:10.1103/physrevlett.108.174301Kekuié, A. (1866). Untersuchungen über aromatische Verbindungen Ueber die Constitution der aromatischen Verbindungen. I. Ueber die Constitution der aromatischen Verbindungen. Annalen der Chemie und Pharmacie, 137(2), 129-196. doi:10.1002/jlac.18661370202Read, N., & Green, D. (2000). Paired states of fermions in two dimensions with breaking of parity and time-reversal symmetries and the fractional quantum Hall effect. Physical Review B, 61(15), 10267-10297. doi:10.1103/physrevb.61.10267Fu, L., & Kane, C. L. (2008). Superconducting Proximity Effect and Majorana Fermions at the Surface of a Topological Insulator. Physical Review Letters, 100(9). doi:10.1103/physrevlett.100.096407Nishida, Y., Santos, L., & Chamon, C. (2010). Topological superconductors as nonrelativistic limits of Jackiw-Rossi and Jackiw-Rebbi models. 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Development of biopolymer-based hydrogels from pork collagen for Tissue Engineering

El desarrollo de biomateriales abarca tres etapas diferentes: selección de materia prima, técnica de procesado y caracterización del producto final. Entre ellos, los hidrogeles se han presentado como candidatos potenciales en aplicaciones farmacéuticas y biomédicas por sus propiedades fisicoquímicas. La mayor parte de los estudios sobre hidrogeles se basan en polímeros naturales por sus excelentes propiedades biológicas. Sin embargo, su procesado es complejo, puesto que se han de controlar parámetros como el tiempo de gelificación, el pH de la disolución y la temperatura de gelificación. No obstante, también es importante seleccionar y caracterizar adecuadamente la materia prima, ya que afecta a las propiedades de los hidrogeles obtenidos. Por tanto, el objetivo de este trabajo es optimizar el proceso de fabricación de hidrogeles de colágeno, evaluando tanto la materia prima a utilizar como los parámetros de procesado que pueden influir en el proceso. Dicha evaluación se ha llevado a cabo mediante el estudio de sus propiedades mecánicas, morfológicas y biológicas. Los resultados muestran como los parámetros definidos durante el procesado del hidrogel son claves en las propiedades finales obtenidas. Además, algunos de ellos presentan adecuadas propiedades para su potencial uso en Ingeniería de Tejidos.The development of biomaterials encompasses three different stages: selection of the raw material, processing technique and characterization of the final product. Among them, hydrogels have been presented as potential candidates in pharmaceutical and biomedical applications due to their physicochemical properties. Most of the studies about hydrogels are based on natural polymers for their excellent biological properties. However, their processing is complex, since several parameters need to be controlled such as gelation time, pH of the solution and gelation temperature. Nevertheless, it is also important to select and characterize the raw material before the fabrication of the hydrogels. Therefore, the objective of the work is to optimize the hydrogel fabrication, evaluating both the raw material to be used and the processing parameters that can influence the process. This evaluation has been carried out by studying its mechanical, morphological and biological properties. Results show how the parameters defined during the hydrogel processing are essential in the final properties obtained. In addition, some of the systems have suitable properties for their potential use in Tissue Engineering.Ministerio de Ciencia e Innovación-Agencia Estatal de Investigación (España) RTI2018-097100-B-C21Ministerio de Educación y Formación Profesional (España) FPU2017/0171

Biocompatible and Thermoresistant Hydrogels Based on Collagen and Chitosan

Hydrogels are considered good biomaterials for soft tissue regeneration. In this sense, collagen is the most used raw material to develop hydrogels, due to its high biocompatibility. However, its low mechanical resistance, thermal stability and pH instability have generated the need to look for alternatives to its use. In this sense, the combination of collagen with another raw material (i.e., polysaccharides) can improve the final properties of hydrogels. For this reason, the main objective of this work was the development of hydrogels based on collagen and chitosan. The mechanical, thermal and microstructural properties of the hydrogels formed with different ratios of collagen/chitosan (100/0, 75/25, 50/50, 25/75 and 0/100) were evaluated after being processed by two variants of a protocol consisting in two stages: a pH change towards pH 7 and a temperature drop towards 4 °C. The main results showed that depending on the protocol, the physicochemical and microstructural properties of the hybrid hydrogels were similar to the unitary system depending on the stage carried out in first place, obtaining FTIR peaks with similar intensity or a more porous structure when chitosan was first gelled, instead of collagen. As a conclusion, the synergy between collagen and chitosan improved the properties of the hydrogels, showing good thermomechanical properties and cell viability to be used as potential biomaterials for Tissue Engineering.Ministerio de Ciencia e Innovación RTI2018-097100-B-C2

Fructose crosslinked scaffolds obtained with collagen via freeze-drying for Tissue Engineering

La Ingeniería de Tejidos ha propiciado el desarrollo de andamios con mejores propiedades que pueden cumplir su propósito de una mejor regeneración de tejidos, mejorando consecuentemente la calidad de vida de las personas. Los andamios son matrices cuya función principal es dar soporte a la adhesión celular y su posterior crecimiento, lo que lleva a la regeneración del tejido dañado. El colágeno es una de las proteínas más abundantes en animales y biopolímero ampliamente utilizado en Ingeniería de Tejidos, por su estructura, biocompatibilidad y la facilidad de su modificación y procesabilidad. En este estudio se prepararán y caracterizarán andamios de colágeno con diferentes concentraciones y técnicas de procesamiento, mediante la obtención de hidrogeles y aerogeles, atendiendo especialmente a su morfología y propiedades mecánicas. Además, se utilizó fructosa como agente químico de entrecruzamiento para estudiar su influencia en las propiedades de los andamios. Los resultados obtenidos revelaron que los andamios con mayores concentraciones de colágeno eran más rígidos y deformables. Comparando ambos sistemas, los aerogeles eran más rígidos pero los hidrogeles, aunque más deformables y con mayor homogeneidad de tamaño de poro. La adición de fructosa produjo un ligero aumento de la deformación crítica, junto con un aumento del módulo elástico.Tissue Engineering has led to the development of this field by designing scaffolds with better properties that can fulfill its purpose of better tissue regeneration, consequently improving people’s quality of life. Scaffolds are matrix, predominantly composed by polymeric materials, which main function is giving support to cell adhesion and the subsequently growth, leading to the regeneration of the damaged tissue. Collagen is one of the most abundant proteins in animals and widely used biopolymer in Tissue Engineering, due to its structure, biocompatibility and the ease of its modification and processability. In this study, collagen scaffolds with different concentrations and processing techniques, by obtaining hydrogels and aerogels, will be prepared and then characterized, specially looking at its morphology and mechanical properties. Moreover, fructose was added as a chemical crosslinking agent to study the influence on scaffolds’ properties. The results obtained revealed that scaffolds with higher collagen concentrations were stiffer and more deformable. Comparing both systems, aerogels were stiffer but hydrogels were more deformable and with higher pore size homogeneity. Fructose addition produced a slight increase in the critical strain, together with an increase in the elastic modulus.MINECO/AEI/FEDER, EU RTI2018-097100-B-C21Ministerio de Educación y Formación Profesional FPU2017/0171

Diseño de un modelo de evaluación de prácticas de las asignaturas de derecho

Memoria ID12-0253. Ayudas de la Universidad de Salamanca para la innovación docente, curso 2012-2013

Experiencias en la tutorización de enseñanzas técnicas

El PAT en la Escuela Politécnica está abierto a todos aquellos tutores que deseen formar parte del plan y también a todos los alumnos, que, voluntariamente pueden marcar la opción de participar en el plan en la matrícula, y también a aquellos que, a pesar de no marcar la opción en la matrícula, finalmente han decidido seguir el plan de acción tutorial. Esta característica de participación e inscripción voluntaria permite que el trabajo se realice más satisfactoriamente tanto por parte de tutores como por parte de los alumnos, puesto que han decidido seguir el plan por ello mismos y no como una imposición. Con este trabajo nos proponemos presentar nuestras experiencias en el desarrollo de la tutorización de nuestros estudiantes así como la evolución en el desarrollo de la tutorización por pares