Biodegradable Natural Hydrogels for Tissue Engineering, Controlled Release, and Soil Remediation

This article provides insights into hydrogels of the most promising biodegradable natural polymers and their mechanisms of degradation, highlighting the different possibilities of controlling hydrogel degradation rates. Since biodegradable hydrogels can be designed as scaffolding materials to mimic the physical and biochemical properties of natural tissues, these hydrogels have found widespread application in the field of tissue engineering and controlled release. In the same manner, their potential as water reservoirs, macro- and microelement carriers, or matrixes for the selective adsorption of pollutants make them excellent candidates for sustainable soil amendment solutions. Accordingly, this article summarizes the recent advances in natural biodegradable hydrogels in the fields of tissue engineering, controlled release, and soil remediation, emphasizing the new opportunities that degradability and its tunability offer for the design and applicability of hydrogels.This research was funded by European Union’s Horizon Europe (SYMBIOREM Grant agreement ID: 101060361), the Basque government (ELKARTEK, grant KK-2023/00056, Grupos Consolidados (IT1756-22)), and the Ministry of Science and Innovation, project PID2022-138572OB-C42 funded by MCIN/AEI/10.13039/501100011033/FEDER, UE

Magnetically Responsive Melt Electrowritten Structures

While melt electrowriting (MEW) can result in complex microstructures, research demonstrating such fabrication with active materials is limited. Herein, magnetoresponsive poly(ε-caprolactone) (PCL) inks containing up to 10 wt% of iron-oxide (Fe3O4) nanoparticles are used to produce fiber with diameters of 9.2 ± 0.6 µm in ordered microstructures when processed by MEW. Introducing the Fe3O4 nanoparticles has a minimal overall effect on printing quality compared to pure PCL under similar conditions. The magnetic response of Fe3O4 containing fibers allows magnetic actuation, which is one of the first steps to control movement in such structures. Printed samples show different magnetic responses that can be controlled by the micro- and macro-structure design, the nanoparticle concentration, and multi-material design. The potential of MEW to print active magnetic complex micro- and macro-structures for 4D printing designs is demonstrated, in which active properties can be further tailored with magnetoresponsive fillers with varying characteristics and by changing MEW fiber diameters.The support of the University of the Basque Country (UPV/EHU) for the Margarita Salas postdoctoral grant for P.G.S. under the “Convocatoria de ayudas para la recualificación del sistema universitario español para 2021–2023” and for the Open Access funding is gratefully acknowledged. The financial support from the Wu Tsai Human Performance Alliance and the Joe and Clara Tsai Foundation is appreciated

Remote sensing chlorophyll a of optically complex waters (rias Baixas, NW Spain): Application of a regionally specific chlorophyll a algorithm for MERIS full resolution data during an upwelling cycle

This study takes advantage of a regionally specific algorithm and the characteristics of Medium Resolution Imaging Spectrometer (MERIS) in order to deliver more accurate, detailed chlorophyll a (chla) maps of optically complex coastal waters during an upwelling cycle. MERIS full resolution chla concentrations and in situ data were obtained on the Galician (NW Spain) shelf and in three adjacent rias (embayments), sites of extensive mussel culture that experience frequent harmful algal events. Regionally focused algorithms (Regional neural network for rias Baixas or NNRB) for the retrieval of chla in the Galician rias optically complex waters were tested in comparison to sea-truth data. The one that showed the best performance was applied to a series of six MERIS (FR) images during a summer upwelling cycle to test its performance. The best performance parameters were given for the NN trained with high-quality data using the most abundant cluster found in the rias after the application of fuzzy c-mean clustering techniques (FCM). July 2008 was characterized by three periods of different meteorological and oceanographic states. The main changes in chla concentration and distribution were clearly captured in the images. After a period of strong upwelling favorable winds a high biomass algal event was recorded in the study area. However, MERIS missed the high chlorophyll upwelled water that was detected below surface in the ria de Vigo by the chla profiles, proving the necessity of in situ observations. Relatively high biomass “patches” were mapped in detail inside the rias. There was a significant variation in the timing and the extent of the maximum chla areas. The maps confirmed that the complex spatial structure of the phytoplankton distribution in the rias Baixas is affected by the surface currents and winds on the adjacent continental shelf. This study showed that a regionally specific algorithm for an ocean color sensor with the characteristics of MERIS in combination with in situ data can be of great help in chla monitoring, detection and study of high biomass algal events in an area affected by coastal upwelling such as the rias Baixas

Synthesis and Characterization of Covalently Crosslinked pH-Responsive Hyaluronic Acid Nanogels: Effect of Synthesis Parameters

Stable hyaluronic acid nanogels were obtained following the water-in-oil microemulsion method by covalent crosslinking with three biocompatible crosslinking agents: Divinyl sulfone, 1,4-butanediol diglycidyl ether (BDDE), and poly(ethylene glycol) bis(amine). All nanoparticles showed a pH-sensitive swelling behavior, according to the pKa value of hyaluronic acid, as a consequence of the ionization of the carboxylic moieties, as it was corroborated by zeta potential measurements. QELS studies were carried out to study the influence of the chemical structure of the crosslinking agents on the particle size of the obtained nanogels. In addition, the effect of the molecular weight of the biopolymer and the degree of crosslinking on the nanogels dimensions was also evaluated for BDDE crosslinked nanoparticles, which showed the highest pH-responsive response.This research was funded by the Government of the Basque Country (Grupos de Investigación, IT718-13, Frontiers, Programas Hazitek 2017–2018)

Pseudo-nitzschia Blooms in a Coastal Upwelling System: Remote Sensing Detection, Toxicity and Environmental Variables

The NW coast of the Iberian Peninsula is dominated by extensive shellfish farming, which places this region as a world leader in mussel production. Harmful algal blooms in the area frequent lead to lengthy harvesting closures threatening food security. This study developed a framework for the detection of Pseudo-nitzschia blooms in the Galician rias from satellite data (MERIS full-resolution images) and identified key variables that affect their abundance and toxicity. Two events of toxin-containing Pseudo-nitzschia were detected (up to 2.5 μg L−1 pDA) in the area. This study suggests that even moderate densities of Pseudo-nitzschia in this area might indicate high toxin content. Empirical models for particulate domoic acid (pDA) were developed based on MERIS FR data. The resulting remote-sensing model, including MERIS bands centered around 510, 560, and 620 nm explain 73% of the pDA variance (R2 = 0.73, p < 0.001). The results show that higher salinity values and lower Si(OH)4/N ratios favour higher Pseudo-nitzschia spp. abundances. High pDA values seem to be associated with relatively high PO43, low NO3− concentrations, and low Si(OH)4/N. While MERIS FR data and regionally specific algorithms can be useful for detecting Pseudo-nitzschia blooms, nutrient relationships are crucial for predicting the toxicity of these blooms

Drug Delivery from Hyaluronic Acid-BDDE Injectable Hydrogels for Antibacterial and Anti-Inflammatory Applications

Hyaluronic acid (HA) injectable biomaterials are currently applied in numerous biomedical areas, beyond their use as dermal fillers. However, bacterial infections and painful inflammations are associated with healthcare complications that can appear after injection, restricting their applicability. Fortunately, HA injectable hydrogels can also serve as drug delivery platforms for the controlled release of bioactive agents with a critical role in the control of certain diseases. Accordingly, herein, HA hydrogels were crosslinked with 1 4-butanediol diglycidyl ether (BDDE) loaded with cefuroxime (CFX), tetracycline (TCN), and amoxicillin (AMX) antibiotics and acetylsalicylic acid (ASA) anti-inflammatory agent in order to promote antibacterial and anti-inflammatory responses. The hydrogels were thoroughly characterized and a clear correlation between the crosslinking grade and the hydrogels’ physicochemical properties was found after rheology, scanning electron microscopy (SEM), thermogravimetry (TGA), and differential scanning calorimetry (DSC) analyses. The biological safety of the hydrogels, expected due to the lack of BDDE residues observed in 1H-NMR spectroscopy, was also corroborated by an exhaustive biocompatibility test. As expected, the in vitro antibacterial and anti-inflammatory activity of the drug-loaded HA-BDDE hydrogels was confirmed against Staphylococcus aureus by significantly decreasing the pro-inflammatory cytokine levels.This research was funded by the i+Med S. Coop., Basque Government (FRONTIERS project, ELKARTEK program, HAZITEK program: IMABI exp number ZE-2019/00012), and the Department of Development and Infrastructures of the Basque Country. Jon Andrade del Olmo thanks the Basque Government for the “Program of Industrial Doctorates. Bikaintek 2018” (exp. number 01-AF-W2-2018-00002)

Predicting the effects of climate change on future freshwater fish diversity at global scale

The aim of the present study was to predict future changes in biodiversity attributes (richness, rarity, heterogeneity, evenness, functional diversity and taxonomic diversity) of freshwater fish species in river basins around the world, under different climate scenarios. To do this, we use a new methodological approach implemented within the ModestR software (NOO3D) which allows estimating simple species distribution predictions for future climatic scenarios. Data from 16,825 freshwater fish species were used, representing a total of 1,464,232 occurrence records. WorldClim 1.4 variables representing average climate variables for the 1960¿1990 period, together with elevation measurements, were used as predictors in these distribution models, as well as in the selection of the most important variables that account for species distribution changes in two scenarios (Representative Concentration Pathways 4.5 and 6.0). The predictions produced suggest the extinction of almost half of current freshwater fish species in the coming decades, with a pronounced decline in tropical regions and a greater extinction likelihood for species with smaller body size and/or limited geographical ranges.We acknowledge institutional support from the Unit of Information Resources for Research at the Unit of Information Resources for Research at the "Consejo Superior de Investigaciones Científicas" (CSIC) for the article-processing charges contribution

A procedure to assess the spatial variability in the importance of abiotic factors affecting distributions: the case of world freshwater fishes

Understanding the factors shaping species' distributions is a key longstanding topic in ecology with unresolved issues. The aims were to test whether the relative contribution of abiotic factors that set the geographical range of freshwater fish species may vary spatially and/or may depend on the geographical extent that is being considered. The relative contribution of factors, to discriminate between the conditions prevailing in the area where the species is present and those existing in the considered extent, was estimated with the instability index included in the R package SPEDInstabR. We used 3 different extent sizes: 1) each river basin where the species is present (local); 2) all river basins where the species is present (regional); and 3) the whole Earth (global). We used a data set of 16,543 freshwater fish species with a total of 845,764 geographical records, together with bioclimatic and topographic variables. Factors associated with temperature and altitude show the highest relative contribution to explain the distribution of freshwater fishes at the smaller considered extent. Altitude and a mix of factors associated with temperature and precipitation were more important when using the regional extent. Factors associated with precipitation show the highest contribution when using the global extent. There was also spatial variability in the importance of factors, both between species and within species and from region to region. Factors associated with precipitation show a clear latitudinal trend of decreasing in importance toward the equator

El Valle del río Guasimal, un Geositio de interés turístico local en Pinar del Río, Cuba

The initiatives for the development of sustainable local tourism that have extended in Cuba, in general, are based on key factors such as the potential of the natural heritage and the richness of rural culture in the territory. In this sense, the singularities of the flora and fauna, their state of conservation and the aesthetic and scenic aspects of the landscape, are considered among the main elements of the Rocío de Sol Tourist Center Project. For this contribution, the geological features of the Guasimal river valley as an attraction of tourist interest and heritage value, based on the documentary review, cartographic analysis and field work. The identification and characterization of singular elements and a variety of interests were achieved, highlighting the geomorphological, hydrological, stratigraphic, tectonic and didactic. On the other hand, the inventory documentation was obtained, which substantiates the proposal to the Institute of Geology Paleontology of Cuba, for the declaration and recognition of the environment as a Geosite, according to Resolution 82 of the Ministry of Energy and Mines of the Republic of Cuba, depending on of integration of the geological potential in the local management of the territory and its link with Geotourism practices.Las iniciativas para el desarrollo del turismo local sostenible que se han extendido en Cuba, de manera general, se basan en factores clave como las potencialidades del patrimonio natural y la riqueza de la cultura rural en el territorio. En este sentido, las singularidades de la flora y la fauna, su estado de conservación y los aspectos estéticos y escénicos del paisaje, se consideran entre los principales elementos del Proyecto Centro Turístico Local “Rocío de Sol”. Para esta contribución, se evaluaron los rasgos geológicos del valle del río Guasimal como atractivo de interés turístico y valor patrimonial, a partir de la revisión documental, análisis cartográfico y el trabajo de campo. Se logró la identificación y caracterización de elementos singulares y variedad de intereses, destacando el geomorfológico, hidrológico, estratigráfico, tectónico y didáctico. Por otra parte, se obtuvo la documentación de inventario, que permitió fundamentar la propuesta al Instituto de Geología y Paleontología de Cuba, para la declaración y reconocimiento del entorno como Geositio, según Resolución 82 del Ministerio de Energía y Minas de la República de Cuba, en función de la integración del potencial geológico en la gestión local del territorio y su vinculación con prácticas de Geoturismo

Contribución al estudio de la combustión de biomasa en lecho fijo: análisis de la fase limitada por oxígeno

Diversos trabajos se llevan a cabo en la actualidad en quemadores experimentales de biomasa de lecho fijo. Su geometría simplificada, la obtención precisa de datos intra-lecho y su elevada operatividad han contribuido al desarrollo de estos sistemas [1-3]. A pesar de la gran cantidad de estudios desarrollados, todavía existe cierta discrepancia o falta de información acerca de la estructura interna del lecho. Con esto en mente, el presente trabajo pretende establecer algunas ideas generales a cerca del proceso de combustión en el lecho o zona de entrada de aire primario (gasificación), enfocada en la fase de combustión heterogénea de char bajo condiciones limitadas por la ausencia de oxígeno. Para ello, se analizan datos experimentales de un quemador de alimentación inferior con aire zonificado en términos de régimen de combustión y relación estequiométrica. Los resultados muestran una clara relación entre la tasa de combustión y el reparto de aire 1º/2º. Además, cuanto mayor es el suministro de aire, mayor es el consumo de combustible. En esencia, el incremento de material gasificado (volatilizado) en la zona de combustión primaria reacciona adecuadamente con el aire secundario, liberando mayor calor y evitando que se alcance la situación de enfriamiento por convección. Como consecuencia, el rango de aire de trabajo útil obtenido es muy amplio, pero el exceso con el que se produce (λ) se mantienen aproximadamente constante. Dicho de otro modo, existe un incremento proporcional entre el caudal de aire suministrado y el combustible quemado. Profundizando en el análisis de la fase de combustión heterogénea, se encontró que la tasa de consumo es proporcional al suministro de aire primario, independientemente del reparto aplicado. Esto indica que la tasa de reacción depende exclusivamente de la tasa de suministro de oxígeno al lecho o frente de reacción. De hecho, el exceso de aire referido a la combustión completa de char para obtener CO2 (λC) se mantiene constante y cercano al estequiométrico. Los resultados mencionados parecen respaldar la idea de que la tasa de reacción de char (oxidación y reducción) en un quemador de alimentación inferior y con reparto de aire está limitada por la presencia de oxígeno en un amplio rango de trabajo. En estas condiciones, la tasa de reacción viene determinada totalmente por el suministro de aire primario, de manera casi independiente a otras variables operativas.Los autores agradecen el apoyo financiero del Ministerio de Economía y Competitividad a través del proyecto ENE2012-36405