Development of in situ forming, polysaccharide-based, self-healable and printable hydrogels por soft actuators and biomedical applications.

316 p.La impresión 4D se presenta como una alternativa prometedora para el desarrollo de materiales para la biomedicina. Hidrogeles preparados mediante impresión 3D capaces de variar su forma en respuesta a estímulos externos constituyen este tipo de sistemas. Estos hidrogeles 4D son sustratos con la capacidad única de adaptarse e imitar los complejos microambientes dinámicos existentes durante los procesos naturales de crecimientos y diferenciación celular. Este carácter dinámico está basado en interacciones físicas/químicas específicas que a su vez son la base para la formación de los denominados hidrogeles in situ, capaces de formarse únicamente ante variaciones específicas del medio. Estos geles in situ, se conocen como los sustratos más eficaces dentro de las nuevas terapias personalizadas de medicina regenerativa.Es por eso que, esta tesis pretende desarrollar hidrogeles in situ adaptables a la tecnología de impresión 3D que sean biodegradables y que muestren adecuadas propiedades mecánicas y capacidad de responder variando su forma ante estímulos externos (pH/iones, temperatura, luz, campo eléctrico y/o magnético) así como habilidad para auto-repararse. Para el desarrollo de estos nuevos materiales con propiedades avanzadas se han seleccionado 3 polisacáridos, el quitosano, ácido hialurónico y alginato, como materiales para la formación de todos los hidrogeles presentados a lo largo de la tesis doctoral. La impresión 4D se presenta como una alternativa prometedora para el desarrollo de materiales para la biomedicina. Hidrogeles preparados mediante impresión 3D capaces de variar su forma en respuesta a estímulos externos constituyen este tipo de sistemas. Estos hidrogeles 4D son sustratos con la capacidad única de adaptarse e imitar los complejos microambientes dinámicos existentes durante los procesos naturales de crecimientos y diferenciación celular. Este carácter dinámico está basado en interacciones físicas/químicas específicas que a su vez son la base para la formación de los denominados hidrogeles in situ, capaces de formarse únicamente ante variaciones específicas del medio. Estos geles in situ, se conocen como los sustratos más eficaces dentro de las nuevas terapias personalizadas de medicina regenerativa.Es por eso que, esta tesis pretende desarrollar hidrogeles in situ adaptables a la tecnología de impresión 3D que sean biodegradables y que muestren adecuadas propiedades mecánicas y capacidad de responder variando su forma ante estímulos externos (pH/iones, temperatura, luz, campo eléctrico y/o magnético) así como habilidad para auto-repararse. Para el desarrollo de estos nuevos materiales con propiedades avanzadas se han seleccionado 3 polisacáridos, el quitosano, ácido hialurónico y alginato, como materiales para la formación de todos los hidrogeles presentados a lo largo de la tesis doctoral

Photocrosslinkable and self-healable hydrogels of chitosan and hyaluronic acid.

Biocompatible and biodegradable hydrogels with biomimetic properties, such as self-repairing, are increasingly interesting for biomedical applications, particularly when they can be printed or in situ formed to mimic extracellular matrix or as personalized implantable devices in tissue regeneration or drug delivery. Photocrosslinkable hydrogels based on methacrylated chitosan (CHIMe) and hyaluronic acid that exhibit according with their composition, tuneable physico-chemical properties are here presented. The study of the conversion, gelation time, mechanical and rheological properties of photopolymerized CHIMe showed an optimal phenyl-2,4,6-trimethylbenzoylphosphinate (LAP) initiator feed (0.1% w). These photocrosslinkable hydrogels demonstrated being able to promote doubly crosslinked hydrogels with similar Young Moduli regardless the cycles of self-healing processes, and tailored swelling (25-70 swelling factor), mechanical (1*10-4-2*10-2MPa) and rheological properties, as a function of polysaccharides relative content. Clear evidences have been found that fast photopolymerization of CHIMe/HA solutions leads to biocompatible (>80% cell viability), biodegradable (20-24days in hydrolytic medium) and robust self-healable hydrogels suitable for advanced biomedical and tissue engineering applications.The authors acknowledge funding by Spanish State Research Agency (AEI) and the European Regional Development Fund (ERFD) through the project PID2019-106099RB-C43/AEI/10.13039/501100011033, as well as, from the Basque Government Industry Department under the ELKARTEK program (KK-2021/00040). The authors thank Dra. Cristina Eguizabal for giving them access to the laboratory “Cell Therapy, Stem Cells and Tissue” at the Basque Center of Transfusion and Human at the Galdako hospital. Technical and human support provided by SGIker (UPV/EHU, MICINN, GV/EJ, EGEF and ESF) is gratefully acknowledged

Dynamic and Self-Healable Chitosan/Hyaluronic Acid-Based In Situ-Forming Hydrogels

In situ-forming, biodegradable, and self-healing hydrogels, which maintain their integrity after damage, owing to dynamic interactions, are essential biomaterials for bioapplications, such as tissue engineering and drug delivery. This work aims to develop in situ, biodegradable and self-healable hydrogels based on dynamic covalent bonds between N-succinyl chitosan (S-CHI) and oxidized aldehyde hyaluronic acid (A-HA). A robust effect of the molar ratio of both S-CHI and A-HA was observed on the swelling, mechanical stability, rheological properties and biodegradation kinetics of these hydrogels, being the stoichiometric ratio that which leads to the lowest swelling factor (×12), highest compression modulus (1.1·10−3 MPa), and slowest degradation (9 days). Besides, a rapid (3 s) self-repairing ability was demonstrated in the macro scale as well as by rheology and mechanical tests. Finally, the potential of these biomaterials was evidenced by cytotoxicity essay (>85%).This research was funded by Spanish State Research Agency (AEI) and the European Regional Development Fund (ERFD) through the project PID2019-106099RB-C43/AEI/10.13039/501100011033, as well as from the Basque Government Industry Department under the ELKARTEK (KK-2021/00040) program

pH-Induced 3D Printable Chitosan Hydrogels for Soft Actuation

Three-dimensional (3D) printing represents a suitable technology for the development of biomimetic scaffolds for biomedical and tissue engineering applications. However, hydrogel-based inks’ printability remains a challenge due to their restricted print accuracy, mechanical properties, swelling or even cytotoxicity. Chitosan is a natural-derived polysaccharide that has arisen as a promising bioink due to its biodegradability, biocompatibility, sustainability and antibacterial properties, among others, as well as its ability to form hydrogels under the influence of a wide variety of mechanisms (thermal, ionic, pH, covalent, etc.). Its poor solubility at physiological pH, which has traditionally restricted its use, represents, on the contrary, the simplest way to induce chitosan gelation. Accordingly, herein a NaOH strong base was employed as gelling media for the direct 3D printing of chitosan structures. The obtained hydrogels were characterized in terms of morphology, chemical interactions, swelling and mechanical and rheological properties in order to evaluate the influence of the gelling solution’s ionic strength on the hydrogel characteristics. Further, the influence of printing parameters, such as extrusion speed (300, 600 and 800 mm/min) and pressure (20–35 kPa) and the cytocompatibility were also analyzed. In addition, printed gels show an electro-induced motion due to their polycationic nature, which highlights their potential as soft actuators and active scaffolds.This research was funded by Spanish State Research Agency (AEI) and the European Regional Development Fund (ERFD) through the project PID2019-106099RB-C43/AEI/10.13039/501100011033, as well as the Basque Government Industry Department under the ELKARTEK programme (KK-2021/00040 and KK-2021/00082)

Polysaccharide-Based In Situ Self-Healing Hydrogels for Tissue Engineering Applications

In situ hydrogels have attracted increasing interest in recent years due to the need to develop effective and practical implantable platforms. Traditional hydrogels require surgical interventions to be implanted and are far from providing personalized medicine applications. However, in situ hydrogels offer a wide variety of advantages, such as a non-invasive nature due to their localized action or the ability to perfectly adapt to the place to be replaced regardless the size, shape or irregularities. In recent years, research has particularly focused on in situ hydrogels based on natural polysaccharides due to their promising properties such as biocompatibility, biodegradability and their ability to self-repair. This last property inspired in nature gives them the possibility of maintaining their integrity even after damage, owing to specific physical interactions or dynamic covalent bonds that provide reversible linkages. In this review, the different self-healing mechanisms, as well as the latest research on in situ self-healing hydrogels, is presented, together with the potential applications of these materials in tissue regeneration.This research was funded by the Spanish State Research Agency (AEI) and the European Regional Development Fund (ERFD) through the project PID2019-106099RB-C43/AEI/10.13039/501100011033. Spanish Ministry of Economy and Competitiveness (MINECO) through the project MAT2016-76039-C4-3-R (AEI/FEDER, UE) and from the Basque Government Industry and Education Department under the ELKARTEK (KK-2020/00068, KK-2020/00099, KK2019/00039 and KK2019/00101), HAZITEK and PIBA (PIBA-2018-06) programs, respectively

A Quasi-Experimental Intervention Protocol to Characterize the Factors that Influence the Acceptance of New Foods by Infants: Mothers' Diet and Weaning Method. Dastatuz Project

Background: Children usually refuse to eat and taste fruits and vegetables; and turning unhealthy eating habits around is an important social challenge in industrialized countries. The Dastatuz project aims to study children food neophobia and to enhance fruit and vegetable acceptance. Methods: A quasi-experimental, multicentre, controlled and prospective intervention study is proposed, in which early factors influencing new food acceptance will be studied. Mothers in the third trimester of pregnancy (n = 144) and their infants will be the study population. Experimental groups will be established based on mothers ' fruit and vegetable intake (standard or high intake) and weaning method (baby lead weaning vs spoon feeding). The project will assess the possible impact of maternal diet and complementary feeding on infants eating behaviour until 18 months of age. Outcome measures will comprise maternal diet and psychological features during pregnancy and breast-feeding (validated questionnaires). Compositional and physicochemical analysis of milk during breastfeeding will also be carried out. During weaning, until 18 months of age, children's diet will be assessed with 24 h recalls and acceptance of new fruits and vegetables will be studied using video recording. Discussion: If the intervention is effective, this research work would have a high potential to be transferred to future public health programs or nutrition guidelines, as a feasible solution to achieve a higher intake of fruits and vegetables among children.This study is supported by the Government of the Basque Country (2019111080

El efecto fotoacústico como técnica de medida de conductividad térmica

Ponencia presentada en las IV Jornadas de Jóvenes Investigadores, celebradas en Madrid el 9 de julio de 2015.La conductividad térmica es una propiedad de los materiales de gran importancia en muchos campos de investigación como por ejemplo, la termoelectricidad. Sin embargo, es una magnitud muy compleja de determinar, especialmente a escala nanométrica. En este trabajo se ha desarrollado un sistema experimental basado en el efecto fotoacústico capaz de medir conductividad térmica de materiales de muy diferentes estructuras, dimensiones y propiedades térmicas. La técnica fotoacústica es una técnica óptica de no contacto que permite obtener la conductividad térmica de diferentes tipos de estructuras desde materiales en volumen, películas delgadas, estructuras multicapa o incluso matrices de nanohilos. En esta técnica, una radiación periódica modulada calienta la muestra de tal forma que el aire en contacto con la superficie de la muestra se caliente y enfría y por tanto se expande y se contrae periódicamente de forma similar a un pistón térmico. Este efecto provoca ondas acústicas que son detectadas por un micrófono. Comparando la onda incidente proveniente del láser con la onda acústica registrada, se pueden extraer las propiedades térmicas de la muestra. El análisis de la señal depende del tipo de muestra que se esté analizando. En este trabajo, se usan dos tipos diferentes de normalización. En el caso de estructuras multicapa, la muestra es iluminada en configuración frontal (o de reflexión) y la señal es normalizada con una muestra de referencia que permite eliminar la contribución de la celda fotoacústica. Para el cálculo de la conductividad térmica se emplea un modelo multicapa desarrollado por Hu et al. En el caso de muestras en volumen, la normalización se lleva a cabo midiendo la muestra tanto en configuración de reflexión como transmisión. El sistema experimental, que se muestra en la figura, fue desarrollado en el laboratorio y consiste en una celda fotoacústica hecha de metacrilato diseñada de tal forma que se evitan posibles resonancias acústicas. En este trabajo, se muestran las capacidades y límites de la técnica junto con algunos resultados experimentales que se han obtenido.Peer Reviewe

Hidrogel injektagarriak eta haien aplikazioak ehun ingeniaritzan

Ehun ingeniaritzak kaltetuta dauden ehunen ordezko funtzionalak sintetizatzeko helburua dauka. Horretarako, zelulaz, molekula bioaktiboz eta euskarri porotsuz osatutako matrizeak beharrezkoak dira, hazkuntza eta zelulen diferentziazio prozesuak gerta daitezen. Matrize hauek solidifikatzeko gai den aitzindari baten injekzioz eratu daitezke kaltetuta dauden ehunetan, hau dela eta, hidrogel injektagarriak ikerkuntza arlo biomedikoan izugarri hedatu dira azken urteotan. Biomaterial hauen injektagarriak izateko gaitasuna sare polimerikoen in-situ gurutzamenduan oinarritzen da. Gurutzamendu hauek, alde batetik, interakzio fisiko itzulgarrien bidez eman daitezke, hidrogel termosentikorrak, pH sentikorrak edo ionikoak eratuz. Bestaldetik, erreakzio kimikoetan ere oinarritu daitezke zeinetan hidrogel fotopolimerizagarriak edota entzimek katalizatutako gurutzamendu bidezko hidrogelak lor daitezkeen. Lan honek hidrogel injektagarriak sintetizatzeko erabiltzen diren estrategien eta ehun ingeniaritzan ikertutako sistema desberdinen aplikazioen berrikuspen bat egitea du helburu.; Tissue engineering aims to create functional substitutes for damaged or diseased tissues through complex constructions of living cells, bioactive molecules and three-dimensional porous scaffolds that support the union, proliferation and differentiation of cells. These constructions can be formed by injection of a precursor which can solidify into the defective tissue, which has converted biomaterials such as injectable hydrogels into one of the most promising biomedical research areas of recent years. Injectable hydrogels are based on the in-situ crosslinking of polymer networks. The mechanisms involved in the formation of these gels can be very varied, and are based on both reversible physical interactions, forming thermosensitive hydrogels, sensitive or ionic pH, and chemical reactions, as is the case of photocrosslinked hydrogels or enzymatically crosslinked. This paper aims to review the main strategies currently used for the formation of injectable hydrogels and, in addition, to show brief results on the formation of injectable hydrogels based on chitosan by physical and chemical crosslinking

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)

Fetal Transient Skin Edema in Two Pregnant Women With Coronavirus Disease 2019 (COVID-19)

Altres ajuts: Funding was provided for the Gesta-COVID19 Study by Instituto de Salud Carlos III (ISCIII) (PR(AMI)181/2020) (ISCIII's reference: COV20/00188).Fetal skin edema in the second trimester might be associated with maternal coronavirus disease 2019 (COVID-19). The risk of vertical transmission of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection remains unknown. Positive reverse-transcription polymerase chain reaction (RT-PCR) test results for SARS-CoV-2 infection in neonates and placental tissue have been reported, and immunoglobulin M antibodies have been detected in neonates born to mothers with infection. The first case is a woman at 22 3/7 weeks of gestation with coronavirus disease 2019 (COVID-19) who was admitted to the intensive care unit. In the second case, the patient remained at home with mild symptoms, starting at 20 weeks of gestation. In both cases, fetal skin edema was observed on ultrasound examination while maternal SARS-COV-2 RT-PCR test results were positive and resolved when maternal SARS-COV-2 RT-PCR test results became negative. The RT-PCR test result for SARS-CoV-2 in amniotic fluid was negative in both cases. The two pregnancies are ongoing and uneventful. Transient fetal skin edema noted in these two patients with COVID-19 in the second trimester may represent results of fetal infection or altered fetal physiology due to maternal disease or may be unrelated to the maternal illness