Desarrollo de nuevos hidrogeles para aplicaciones biomédicas

Programa Oficial de Doutoramento en Física Aplicada. 5021V01[Resumen] Los hidrogeles son biomateriales que han recibido una considerable atención como candidatos para un amplio rango de aplicaciones biomédicas. Es por esto, que el diseño de hidrogeles con características óptimas es fundamental para progresar en el área de biomateriales funcionales. El objetivo de esta tesis fue el desarrollo y la caracterización de nuevos hidrogeles basados en biopolímeros para aplicaciones biomédicas como liberación de fármacos, reparación de tejidos y curación de heridas. Para esto, se seleccionaron polímeros sintéticos y naturales para la preparación de hidrogeles interpenetrados y semi-interpenetrados, hidrogeles compuestos incorporando micropartículas e hidrogeles físicos. En primer lugar, se obtuvieron hidrogeles mediante el encapsulamiento de quitosano, pectina o κ-carragenina en hidrogeles a base de metacrilato para mejorar sus propiedades mecánicas y de hinchamiento. En segundo lugar, se preparó un hidrogel compuesto en base a micropartículas de poli(hidroxibutirato-co-hidroxivalerato) cargadas en un hidrogel de κ-carragenina y goma de algarrobo como vehículo de administración dual de fármacos poco solubles en agua. Finalmente, se preparó un hidrogel inyectable que combina iota y kappa carrageninas, goma de algarrobo y gelatina, el cual podría ser útil en la cicatrización de heridas y la reparación de tejidos. Así, la combinación de polímeros de distinto origen y el empleo de diferentes métodos de preparación y tipos de entrecruzamiento permitió obtener hidrogeles con las propiedades adecuadas para un potencial uso en determinadas aplicaciones, como la liberación de fármacos, reparación de tejidos y curación de heridas[Resumo] Os hidroxeles son biomateriais que recibiron unha considerable atención como candidatos para un amplo rango de aplicacións biomédicas. É por isto, que o deseño de hidroxeles con características óptimas é fundamental para progresar na área de biomateriais funcionais. O obxectivo desta tese foi o desenvolvemento e a caracterización de novos hidroxeles baseados en biopolímeros para aplicacións biomédicas como liberación de fármacos, reparación de tecidos e curación de feridas. Para isto, seleccionáronse polímeros sintéticos e naturais para a preparación de hidroxeles interpenetrados e semi- interpenetrados, hidroxeles compostos incorporando micropartículas e hidroxeles físicos. En primeiro lugar, obtivéronse hidroxeles mediante o encapsulamento de quitosano, pectina ou κ- carragenina en hidroxeles a base de metacrilato para mellorar as súas propiedades mecánicas e de inchamento. En segundo lugar, preparouse un hidroxel composto en base a micropartículas de poli(hidroxibutirato- co- hidroxivalerato) cargadas nun hidroxel de κ- carragenina e goma de algarrobo como vehículo de administración dual de fármacos pouco solubles en auga. Finalmente, preparouse un hidroxel inxectable que combina iota e kappa carrageninas, goma de algarrobo e xelatina, o cal podería ser útil na cicatrización de feridas e a reparación de tecidos. Así, a combinación de polímeros de distinto orixe e o emprego de diferentes métodos de preparación e tipos de entrecruzamento permitiu obter hidroxeles coas propiedades axeitadas para un potencial uso en determinadas aplicacións, como a liberación de fármacos, a reparación de tecidos e a curación de feridas.[Abstract] Hydrogels are biomaterials that have received increasing attention as candidate for a wide range of biomedical applications. Therefore, the design of hydrogels with optimal characteristics is fundamental to progress in the area of functional biomaterials. The objective of this thesis was the development and characterization of novel biopolymer-based hydrogels for biomedical applications such as drug delivery, tissue repair and wound healing. For this purpose, synthetic and natural polymers were selected for the preparation of interpenetrating and semi-interpenetrating polymer networks, composite hydrogels incorporating microparticles and physical hydrogels. Firstly, hydrogels were obtained by the entrapment of chitosan, pectin or κ-carrageenan within methacrylate- based hydrogels to improve their swelling and the mechanical properties. Secondly, a composite hydrogel based on PHBV microparticles loaded in κ-carrageenan/locust bean gum hydrogel was prepared as a dual delivery carrier of poorly water soluble drugs. Finally, an injectable hydrogel was prepared by combining of iota and kappa carrageenan, locust bean gum and gelatin, which could be useful in wound healing and tissue repair. Thus, the combination of polymers of different origin and the use of distinct preparation methods and crosslinkings led to hydrogels with the suitable properties for potential use in some applications, such as drug delivery, tissue repair and wound healing

Preparation of Poly(vinyl Alcohol) Microparticles for Freeze Protection of Sensitive Fruit Crops

[Abstract] Poly(vinyl alcohol) (PVA) displays ice recrystallization inhibition (IRI) properties as many antifreeze proteins found in cold tolerant organisms. The molecular architecture and composition (molecular weight and distribution of pendant OH and acetate groups) have been studied to improve the antifreezing properties of PVA, suggesting that the molecular architecture of PVA plays an important role in IRI activity. The present work deals with the preparation of PVA microparticles using an alkaline treatment. The effect of PVA molecular weight on the morphology and antifreezeing properties of PVA microparticles was investigated. The antifreezeing property of PVA microparticles on the susceptibility of flower bud tissues to freeze damage was also evaluated. The alkaline treatment of an aqueous PVA solution produced stable polymer chain aggregates with spherical shapes. The average size of the PVA microparticles increased significantly with the increasing molecular weight of the PVA macromolecule precursor. The PVA microparticles inhibited the growth of ice crystals and blocked ice growth at concentrations as low as 0.01 % w/v. The effect of impeding ice crystal growth by preventing the joining of adjacent ice crystals is attributed to the larger size of the PVA particles adsorbed on the ice surface compared to the aggregated PVA macromolecules in saline solution. The thermal hysteresis activity of PVA macromolecules and microparticles was not detected by differential scanning calorimetry analysis. The PVA microparticles reduced the incidence of freeze injuries in flower bud tissues by 55% and their application, considering the low toxicity of PVA, has a high potential for freeze protection in fruit crops.Chile. Comisión Nacional de Investigación Científica y Tecnológica; ID16I10425Chile. Comisión Nacional de Investigación Científica y Tecnológica; ID16I20425Chile. Gobierno Regional del Biobío; R17A10003Chile. Agencia Nacional de Investigación y Desarrollo; ACE210016Chile. Agencia Nacional de Investigación y Desarrollo; ACE210012Chile. Comisión Nacional de Investigación Científica y Tecnológica; AFB170007This research was funded by projects CONICYT + FONDEF/tercer concurso IDeA en Dos Etapas del Fondo al Desarrollo Científico Y Tecnológico, FONDEF/CONICYT 2016 [grant numbers ID16I10425 and ID16I20425], CIPA, ANID Regional, GORE BIO BIO [grant number: R17A10003], ANID [grant numbers: ACE210016 and ACE210012] and CONICYT PIA/APOYO CCTE [grant number: AFB170007

Injectable hybrid hydrogels physically crosslinked based on carrageenan and green graphene for tissue repair

Financiado para publicación en acceso aberto: Universidade da Coruña/CISUG[Abstract] Injectable and biocompatible novel hybrid hydrogels based on physically crosslinked natural biopolymers and green graphene for potential use in tissue engineering are reported. Kappa and iota carrageenan, locust bean gum and gelatin are used as biopolymeric matrix. The effect of green graphene content on the swelling behavior, mechanical properties and biocompatibility of the hybrid hydrogels is investigated. The hybrid hydrogels present a porous network with three-dimensionally interconnected microstructures, with lower pore size than that of the hydrogel without graphene. The addition of graphene into the biopolymeric network improves the stability and the mechanical properties of the hydrogels in phosphate buffer saline solution at 37 °C without noticeable change in the injectability. The mechanical properties of the hybrid hydrogels were enhanced by varying the dosage of graphene between 0.025 and 0.075 w/v%. In this range, the hybrid hydrogels preserve their integrity during mechanical test and recover the initial shape after removing the applied stress. Meanwhile, hybrid hydrogels with graphene content of up to 0.05 w/v% exhibit good biocompatibility for 3T3-L1 fibroblasts; the cells proliferate inside the gel structure and show higher spreading after 48 h. These injectable hybrid hydrogels with graphene have promising future as materials for tissue repair.Xunta de Galicia; ED431C 2019/17Instituto de Salud Carlos III; CD21/00042Chile. CORFO; 22CVID-20683

Injectable hybrid hydrogels physically crosslinked based on carrageenan and green graphene for tissue repair

Injectable and biocompatible novel hybrid hydrogels based on physically crosslinked natural biopolymers and green graphene for potential use in tissue engineering are reported. Kappa and iota carrageenan, locust bean gum and gelatin are used as biopolymeric matrix. The effect of green graphene content on the swelling behavior, mechanical properties and biocompatibility of the hybrid hydrogels is investigated. The hybrid hydrogels present a porous network with three-dimensionally interconnected microstructures, with lower pore size than that of the hydrogel without graphene. The addition of graphene into the biopolymeric network improves the stability and the mechanical properties of the hydrogels in phosphate buffer saline solution at 37 °C without noticeable change in the injectability. The mechanical properties of the hybrid hydrogels were enhanced by varying the dosage of graphene between 0.025 and 0.075 w/v%. In this range, the hybrid hydrogels preserve their integrity during mechanical test and recover the initial shape after removing the applied stress. Meanwhile, hybrid hydrogels with graphene content of up to 0.05 w/v% exhibit good biocompatibility for 3T3-L1 fibroblasts; the cells proliferate inside the gel structure and show higher spreading after 48 h. These injectable hybrid hydrogels with graphene have promising future as materials for tissue repair.The research leading to these results received funding from the Xunta de Galicia Government: program of consolidation and structuring competitive research units [grant number: ED431C 2019/17]. Y.F. is a ‘Sara Borrell’ researcher funded by Instituto de Salud Carlos III (ISCIII) and co-funded by Fondo Europeo de Desarrollo Regional (FEDER) [CD21/00042]. Thanks to Corfo 22CVID-206836, CIPA, ANID Regional, GORE BIO BIO, R17A10003, ACE210016, ACE210012. Funding for open access charge was provided by Universidade da Coruna/CISU

Grape (Vitis vinifera L. cv. País) Juices Obtained by Steam Extraction

Vitis vinifera L. cv. País is an ancestral Chilean grape undervalued due to its undesirable oenological characteristics. In this study, steam extraction for the production of grape juice, a new product, according to our knowledge, is proposed as an alternative for the valorization of this fruit. The effect of the extraction time on the composition and antioxidant capacity of País grape juice obtained was evaluated, as well as the change in the phenolic profile during storage. The soluble solid values and total polyphenol and total anthocyanin content increased with the extraction time. However, a residence time of the juice in the extraction device higher than 10 min led to thermal degradation of anthocyanins and flavonols. The most abundant phenolic compound identified and quantified by HPLC-DAD in the País grape juice was cinnamic acid. The storage of juices had a greater effect on anthocyanin and flavonol losses than the residence time of the juice in the extraction device. The antioxidant capacity of juice measured by ABTS and ferric reducing power assays ranged from 3 to 5 mmol trolox/L and from 10 to 18 mM Fe2+/L, respectively. In summary, steam extraction is a viable method to produce País grape juice with antioxidant capacity

Donut-Shaped Microparticles Prepared from Different C-Type Starch Sources: Characterization and Encapsulation of Gallic Acid

Donut-shaped microparticles were prepared from starches of different botanical sources by heat-mixture-alcoholic treatment. C-type starch allomorphs: pea, Araucaria araucana, and Aesculus hippocastanum were used for the preparation of the microparticles. The microparticles were characterized and evaluated as a carrier of phenolic compounds. The gallic acid encapsulation efficiency was determined, and its antioxidant activity was evaluated using spectrophotometric assays. The starch microparticles exhibited a round to elongated shape, with a central concavity, similar to donut-shaped microparticles. In the loaded and unloaded starch microparticles, B-type and V-type polymorphs coexist. The entrapment of gallic acid in starch microparticles is due to hydrogen-bond formation and not to an amylose inclusion complex. The loaded pea starch microparticles showed lower onset and peak gelatinization temperature with respect to their unloaded counterpart, which is associated with the decreased stability of formed crystallites. The percentage of phenolic compounds encapsulated depended on the native starch precursor. Pea starch microparticles loaded with gallic acid showed the highest encapsulation efficiency around 45%. Gallic acid entrapped in starch microparticles showed no loss of antioxidant activity. Starch microparticles are a food-grade solid matrix suitable as carriers for active compounds

Starches Isolated from Potatoes Grown in Chile: Characterisation and Nanoparticle Preparation

International audienceThe most widely cultivated varieties of potato in Chile are Patagonia and Asterix. However, there is scarce information about the physical–chemical characteristics of starches isolated from these potatoes. In this study, the starches from two potato varieties, Patagonia and Asterix, were isolated and characterised. In addition, an exploratory study of the preparation of starch nanoparticles from these potato varieties by the flash nanoprecipitation method was performed. The morphology (scanning electron microscopy and optical microscopy), crystallinity (X-ray diffraction), thermal (differential scanning calorimetry), rheological (rapid visco analyser) and hydration properties are reported. Starches from Patagonia potato (PPS) and Asterix potato (APS) were isolated by the wet milling method. PPS and APS had similar starch content on fresh weight basis, around 15%. The granule particle sizes of Chilean potato starches showed a unimodal distribution, in the range of 10–90 µm. Amylose content varied between 23.8 and 25.3% for APS and PPS, respectively, making them normal starches. Gelatinisation temperature and enthalpy were 58.6 and 60.1 °C and 15.5 and 17.8 J/g for APS and PPS, respectively. Significant differences were obtained in the pasting parameters of Chilean potato starches; the rapid visco analyser pasting profiles of PPS exhibited a large viscosity peak and APS did not show a distinctive viscosity peak. The pasting profiles of APS are required for food products such as soups and sauces. Spherical nanoparticles were prepared from the Chilean potato starches by flash nanoprecipitation method using two micromixer devices: confined impinging jet mixer and multi-inlet vortex mixer. The size of potato nanoparticles depended on micromixer device, and the lowest particle size (100 nm) was obtained when the confined impinging jet mixer was used. The nanoparticles from Chilean potato starches are potential raw materials for the nutraceutical, food and pharmaceutical fields