Rheological Properties of Clay Suspensions Treated by Hydrocyclone Process

Suspensions of bentonite clays are usually employed at industrial scale in different processes as drilling fluids as well as adsorbents for removing pollutants in muds or natural waters. For these purposes, avoiding the gravitational settling of the particles is a requirement for achieving a high efficiency and a low cost operation. Unfortunately, the clays in natural deposits are usually mixed with particles of other minerals with similar density, making difficult the separation process by usual gravitational methods. Among the most efficient and lowest cost processes, the separation by hydrocyclone is preferred because of a number of advantages at the industrial scale. In this work we verify, by different experimental methods, the efficiency of this wet separation process for removing impurities in a raw bentonite mineral, and at the same time to transform a calcium bentonite in a sodium one by dissolving sodium carbonate in the liquid phase of the hidrocyclone. Afterwards, we checked by using rheological measurements the best protocol for the preparation of the suspension. We studied the rheological behaviour of clay suspensions, with different degree of impurities removal and with different solid concentration, in order to determine the minimal conditions for obtaining bentonite suspensions that do not suffer from gravitational settling during a long period of time. For this purpose, we investigated the deformation and flow of different suspensions, under steady state and oscillatory shear, and determined when they developed a high enough yield stress and an appropriate elastic response to avoid particle settling. We explain the results in view of the energy of interaction between the different surfaces (faces, edges) of the clay platelets, which favours the formation of a soft gel in which the particles are entrapped in loose flocculi that extent along all the volume of the suspensions.This study was supported by project FIS2013-41821-R (Plan Nacional de Investigación Científica, Desarrollo e Innovación Tecnológica, Ministerio de Economía y Competitividad, Spain, co-funded by ERDF, European Union). Mariem Mekni Abrougui acknowledges financial support from Tunisian Goverment (fellowship program) and UE (Erasmus program) for her stays in the University of Granada

Rheology of magnetic alginate hydrogels

Según Sherpa/Romeo el periodo de embargo es de 12 mesesMagnetic hydrogels are becoming increasingly in demand for technical and biomedical applications, especially for tissue engineering purposes. Among them, alginate-based magnetic hydrogels emerge as one of the preferred formulations, due to the abundance, low cost, and biocompatibility of alginate polymers. However, their relatively slow gelation kinetics provokes strong particle settling, resulting in nonhomogeneous magnetic hydrogels. Here, we study magnetic hydrogels prepared by a novel two-step protocol that allows obtaining macroscopically homogeneous systems, consisting of magnetic microparticles embedded within the alginate network. We describe a comprehensive characterization (morphology, microstructure, and mechanical properties under shear stresses) of the resulting magnetic hydrogels. We pay special attention to the effects of particle volume fraction (up to 0.33) and strength of the magnetic field on the viscoelastic properties of the magnetic hydrogels. Our results indicate that magnetic hydrogels are strongly strengthened against shear stresses as magnetic particle concentration and applied field intensity increase. Finally, we report an adaptation of the two-step protocol for the injection of the magnetic hydrogels that might be adequate for implementation in vivo. Interestingly, injected magnetic hydrogels present similar morphology and mechanical properties to noninjected hydrogels. To conclude, we report magnetic alginate hydrogels with adequate homogeneity and injectability character. These characteristics, together with the broad range of their mechanical properties, make them perfect candidates for cutting-edge technology.FIS2013-41821-R (Plan Nacional de Investigación Científica, Desarrollo e Innovación Tecnológica, MINECO, Spain, cofunded by ERDF, European Union) and FIS2017-85954-R (Ministerio de Economía, Industria y competitividad, MINECO, and Agencia Estatal de Investigación, AEI, Spain, cofunded by Fondo Europeo de Desarrollo Regional, FEDER, European Union). Ministry of Education and Science of the Russian Federation, projects 02.A03.21.0006, 3.1438.2017/4.6, and 3.5214.2017/6.7, as well as to the Russian Fund of Basic Researches, project 18-08-00178. French government, piloted by the National Research Agency (ANR) in the framework of the project Future Investments UCA JEDI, Ref. No. ANR-15-IDEX-01 (RheoGels).

In vivo time-course biocompatibility assessment of biomagnetic nanoparticles-based biomaterials for tissue engineering applications

Novel artificial tissues with potential usefulness in local-based therapies have been generated by tissue engineering using magnetic-responsive nanoparticles (MNPs). In this study, we performed a comprehensive in vivo characterization of bioengineered magnetic fibrin-agarose tissue-like biomaterials. First, in vitro analyses were performed and the cytocompatibility of MNPs was demonstrated. Then, bioartificial tissues were generated and subcutaneously implanted in Wistar rats and their biodistribution, biocompatibility and functionality were analysed at the morphological, histological, haematological and biochemical levels as compared to injected MNPs. Magnetic Resonance Image (MRI), histology and magnetometry confirmed the presence of MNPs restricted to the grafting area after 12 weeks. Histologically, we found a local initial inflammatory response that decreased with time. Structural, ultrastructural, haematological and biochemical analyses of vital organs showed absence of damage or failure. This study demonstrated that the novel magnetic tissue-like biomaterials with improved biomechanical properties fulfil the biosafety and biocompatibility requirements for future clinical use and support the use of these biomaterials as an alternative delivery route for magnetic nanoparticles.• Grants FIS-PI17/0391 and FIS-PI17/0393 from Instituto de Salud Carlos III - ISCIII (Plan Nacional de Investigación Científica, Desarrollo e Innovación Tecnológica I + D + i from the Spanish Ministerio de Ciencia e Innovación), co-financed by ERDF-FEDER, European Union. • Award number AC17/00013 (NanoGSkin) by ISCIII thorough AES 2017 and within the EuroNanoMed framework. • Grant FIS2017-85954-R funded by Ministerio de Economía, Industria y Competitividad, MINECO, and Agencia Estatal de Investigación, AEI, Spain, cofunded by Fondo Europeo de Desarrollo Regional, FEDER, European Union. • Grants CS PI-0257-2017 and CSyF PE-0395-2019 from Consejería de Salud y Familias, Junta de Andalucía, Spain. • Grant n° Res SECYT 411/18 from SECYT (Secretary of Science and Technology of National University of Córdoba, Argentina) • Project Future Investments UCA JEDI, No. ANR-15-IDEX-01, project “RheoGel” by the French “Agence Nationale de la Recherche”

In vitro characterization of a novel magnetic fibrin-agarose hydrogel for cartilage tissue engineering

The encapsulation of cells into biopolymer matrices enables the preparation of engineered substitute tissues. Here we report the generation of novel 3D magnetic biomaterials by encapsulation of magnetic nanoparticles and human hyaline chondrocytes within fibrin-agarose hydrogels, with potential use as articular hyaline cartilagelike tissues. By rheological measurements we observed that, (i) the incorporation of magnetic nanoparticles resulted in increased values of the storage and loss moduli for the different times of cell culture; and (ii) the incorporation of human hyaline chondrocytes into nonmagnetic and magnetic fibrin-agarose biomaterials produced a control of their swelling capacity in comparison with acellular nonmagnetic and magnetic fibrin-agarose biomaterials. Interestingly, the in vitro viability and proliferation results showed that the inclusion of magnetic nanoparticles did not affect the cytocompatibility of the biomaterials. What is more, immunohistochemistry showed that the inclusion of magnetic nanoparticles did not negatively affect the expression of type II collagen of the human hyaline chondrocytes. Summarizing, our results suggest that the generation of engineered hyaline cartilage-like tissues by using magnetic fibrin-agarose hydrogels is feasible. The resulting artificial tissues combine a stronger and stable mechanical response, with promising in vitro cytocompatibility. Further research would be required to elucidate if for longer culture times additional features typical of the extracellular matrix of cartilage could be expressed by human hyaline chondrocytes within magnetic fibrin-agarose hydrogels.This study was supported by projects FIS2013-41821-R (Plan Nacional de Investigación Científica, Desarrollo e Innovación Tecnológica, Ministerio de Economía, Industria y Competitividad, MINECO Spain, cofunded by Fondo Europeo de Desarrollo Regional, FEDER, European Union), FIS2017-85954-R (Ministerio de Economía, Industria y Competitividad, MINECO, and Agencia Estatal de Investigación, AEI, Spain, cofunded by Fondo Europeo de Desarrollo Regional, FEDER, European Union), and by the Consejería de Salud y Familias, Junta de Andalucía, Spain, Grant SAS CS PI-0257-2017

Hidrogeles magnéticos para aplicaciones biomédicas: Estudio de su biocompatibilidad y propiedades viscoelásticas

Los hidrogeles son sistemas formados por una red tridimensional de cadenas poliméricas flexibles entrecruzadas. Estos materiales son capaces de retener una gran cantidad de agua sin disolverse. La red se puede formar por enlaces físicos o químicos entre las cadenas de una gran variedad de polímeros, como alginato o fibrina. En los últimos años se ha desarrollado una nueva generación de hidrogeles, llamados geles supramoleculares, que están formados por péptidos que contienen entre 2 y 12 aminoácidos [1, 2]. En estos geles, los péptidos se auto-asocian mediante interacciones físicas formando una red tridimensional de nanofibras que puede ocluir más de un 99 % de su peso en agua. En los últimos años, se han desarrollado hidrogeles compuestos que contienen micro- o nanopartículas magnéticas para reforzar la red polimérica y, además, conferirle algunas ventajas asociadas a las propiedades de las partículas. Así, la presencia de partículas magnéticas permite la visualización y seguimiento de los hidrogeles magnéticos en aplicaciones in vivo mediante resonancia magnética [3]. Además, estudios in vitro sugieren que la presencia de material magnético en los hidrogeles estimula la adhesión, proliferación y diferenciación celular [4-6]. En tercer lugar, el uso de implantes formados por hidrogeles magnéticos in vivo permitiría atraer hasta ellos partículas magnéticas funcionalizadas, inyectadas en sus proximidades, mediante la acción de campos magnéticos externos [3, 5, 7]. Por último, se ha demostrado que se pueden preparar tejidos biológicos artificiales basados en hidrogeles magnéticos con propiedades mecánicas modulables por campos magnéticos [8]. El objetivo principal de este trabajo ha sido conseguir hidrogeles biocompatibles, con propiedades mecánicas controlables a distancia por campos magnéticos de intensidad H baja a moderada (H < 100 kA/m), para emplearlos como sustitutos de tejidos biológicos en el campo de la ingeniería tisular. Para ello, se han determinado las propiedades mecánicas y magnéticas de distintos tipos de biomateriales y se han realizado ensayos de biocompatibilidad ex vivo e in vivo de los mismos.Tesis Univ. Granada. Programa Oficial de Doctorado en Física y Ciencias del EspacioMinisterio de Economía y Competitividad (MINECO) y por el Fondo Europeo de Desarrollo Regional (FEDER) mediante el proyecto FIS2013-41821-R.Universidad de Granada y el CEI BioTic Granada, convocatoria 2016/2017

Electro-optical Study of the Anomalous Rotational Diffusion in Polymer Solutions

Brownian diffusion of spherical nanoparticles is usually exploited to ascertain the rheological properties of complex media. However, the behavior of the tracer particles is affected by a number of phenomena linked to the interplay between the dynamics of the particles and polymer coils. For this reason, the characteristic lengths of the dispersed entities, depletion phenomena, and the presence of sticking conditions have been observed to affect the translational diffusion of the probes. On the other hand, the retardation effect of the host fluid on the rotational diffusion of nonspherical particles is less understood. We explore the possibility of studying this phenomenon by analyzing the electro-orientation of the particles in different scenarios in which we vary the ratio between the particle and polymer characteristic size, and the geometry of the particles, including both elongated and oblate shapes. We find that the Stokes−Einstein relation only applies if the radius of gyration of the polymer is much shorter than the particle size and when some repulsive interaction between both is present.Junta de AndaluciaEuropean Commission European CommissionMinisterio de Ciencia, Innovaci?n y Universidades, Spain B-FQM-141-UGR18 P18-FR-3583 PGC2018- 098770-B-I00 PID2021-127427NB-I00 A-FQM-492- UGR20 TED2021-131855B-I0

Synthesis, characterization and in vivo evaluation of biocompatible ferrogels

A hydrogel is a 3-Dnetwork of polymer chains in which water is the dispersion medium. Hydrogels have found extensive applications inthe biomedical field due to their resemblance to living tissues.Furthermore, hydrogels can be endowedwith exceptionalproperties by addition of syntheticmaterials. For example, magneticfield-sensitive gels, called ferrogels, are obtained by embedding magnetic particles in the polymer network. Novelliving tissueswith unique magnetic field-sensitive propertieswere recently preparedby 3-D cell culture in biocompatible ferrogels. This talk critically reviews the most recent progress and perspectives intheirsynthesis, characterizationand biocompatibility evaluation. Optimizationof ferrogels for this novel applicationrequires low-density, strongly magnetic, multi-domain particles. Interestingly, the rheological properties of the resulting ferrogelsin the absence of field were largely enhanced with respect to nonmagnetic tissues, which can only be explained by the additional cross-linking imparted by the embeddedmagnetic particles.Remarkably, rheological measurements under an applied magnetic fielddemonstrated that magnetic tissuespresented reversibly tunable mechanical properties, which constitutes a unique advantage with respect to nonmagnetic tissues. In vivo evaluation of ferrogelsshowed good biocompatibility, with only some local inflammatoryresponse, and noparticle migrationor damage to distant organs.Financial support: project FIS2013-41821-R (MINECO, Spain; co-funded by ERDF, European Union); project FIS PI14-1343 funded by the Spanish MINECO (Instituto Carlos III), co-funded by the ERDF of the European Union; AZ also acknowledges the Russian Scientific Foundation, project 14-19-00989

Evaluation of Fibrin-Agarose Tissue-Like Hydrogels Biocompatibility for Tissue Engineering Applications

Generation of biocompatible and biomimetic tissue-like biomaterials is crucial to ensure the success of engineered substitutes in tissue repair. Natural biomaterials able to mimic the structure and composition of native extracellular matrices typically show better results than synthetic biomaterials. The aim of this study was to perform an in vivo time-course biocompatibility analysis of fibrin-agarose tissue-like hydrogels at the histological, imagenological, hematological, and biochemical levels. Tissue-like hydrogels were produced by a controlled biofabrication process allowing the generation of biomechanically and structurally stable hydrogels. The hydrogels were implanted subcutaneously in 25 male Wistar rats and evaluated after 1, 5, 9, and 12 weeks of in vivo follow-up. At each period of time, animals were analyzed using magnetic resonance imaging (MRI), hematological analyses, and histology of the local area in which the biomaterials were implanted, along with major vital organs (liver, kidney, spleen, and regional lymph nodes). MRI results showed no local or distal alterations during the whole study period. Hematology and biochemistry showed some fluctuation in blood cells values and in some biochemical markers over the time. However, these parameters were progressively normalized in the framework of the homeostasis process. Histological, histochemical, and ultrastructural analyses showed that implantation of fibrin-agarose scaffolds was followed by a progressive process of cell invasion, synthesis of components of the extracellular matrix (mainly, collagen) and neovascularization. Implanted biomaterials were successfully biodegraded and biointegrated at 12 weeks without any associated histopathological alteration in the implanted zone or distal vital organs. In summary, our in vivo study suggests that fibrin-agarose tissue-like hydrogels could have potential clinical usefulness in engineering applications in terms of biosafety and biocompatibility.Spanish Plan Nacional de Investigacion Cientifica, Desarrollo e Innovacion Tecnologica (I+D+i) from the Spanish Ministerio de Ciencia, Innovacion y Universidades (Instituto de Salud Carlos III) (ERDF-FEDER, European Union) FIS PI17/0391 PI17/0393 PI18/332ISCIII thorough AES 2017 AC17/00013EuroNanoMed framework AC17/00013Hispanagar, SA, Burgos, Spain, through CDTI, Ministry of Economy and Competitiveness, Spain IDI-20180052Junta de Andalucia CS PI-0257-2017 PE-0395-2019Ministerio de Economia, Industria y Competitividad, MINECO FIS2017-85954-RAgencia Estatal de Investigacion, AEI, Spain FIS2017-85954-REuropean Union (EU) FIS2017-85954-RNational Cordoba University, Argentina Secyt 266 HCS 659/2018Programa Operativo Pluriregional de Crecimiento Inteligente (CRIN) IDI-20180052ERDF-FEDER funds, EU IDI-2018005