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| 2. |
- Fontes-Candia, Cynthia, et al.
(författare)
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Maximizing the oil content in polysaccharide-based emulsion gels for the development of tissue mimicking phantoms
- 2021
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Ingår i: Carbohydrate Polymers. - : Elsevier Ltd. - 0144-8617 .- 1879-1344. ; 256
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Tidskriftsartikel (refereegranskat)abstract
- Formulations based on agar and κ-carrageenan were investigated for the production of emulsion gels applicable as tissue mimicking phantoms. The effects of the polysaccharide matrix, the oil content and the presence of surfactants on the micro-/nanostructure, rheology, and mechanical and dielectric properties were investigated. Results showed a high capacity of the agar to stabilize oil droplets, producing gels with smaller (10−21 μm) and more uniform oil droplets. The addition of surfactants allowed increasing the oil content and reduced the gel strength and stiffness down to 57 % and 34 %, respectively. The permittivity and conductivity of the gels were reduced by increasing the oil content, especially in the agar gels (18.8 and 0.05 S/m, respectively), producing materials with dielectric properties similar to those of low-water content tissues. These results evidence the suitability of these polysaccharides to design a variety of tissue mimicking phantoms with a broad range of mechanical and dielectric properties.
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| 3. |
- Bojorges, Hylenne, et al.
(författare)
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Structural and functional properties of alginate obtained by means of high hydrostatic pressure-assisted extraction
- 2023
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Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617 .- 1879-1344. ; 299
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Tidskriftsartikel (refereegranskat)abstract
- The effects of the high hydrostatic pressure (HPP) pre-treatment on the alginate extraction were seen to greatly depend on the recalcitrant nature of two algae species. Alginates were deeply characterized in terms of composition, structure (HPAEC-PAD, FTIR, NMR, SEC-MALS), functional and technological properties.The pre-treatment significantly increased the alginate yield in the less recalcitrant A. nodosum (AHP) also favoring the extraction of sulphated fucoidan/fucan structures and polyphenols. Although the molecular weight was significantly lower in AHP samples, neither the M/G ratio nor the M and G sequences were modified. In contrast, a lower increase in alginate extraction yield was observed for the more recalcitrant S. latissima after the HPP pre-treatment (SHP), but it significantly affected the M/G values of the resulting extract. The gelling properties of the alginate extracts were also explored by external gelation in CaCl2 solutions. The mechanical strength and nanostructure of the hydrogel beads prepared were determined using compression tests, synchro-tron small angle X-ray scattering (SAXS), and cryo-scanning electron microscopy (Cryo-SEM). Interestingly, the application of HPP significantly improved the gel strength of SHP, in agreement with the lower M/G values and the stiffer rod-like conformation obtained for these samples.
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| 4. |
- Martínez-Sanz, Marta, et al.
(författare)
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Composition and rheological properties of microalgae suspensions : Impact of ultrasound processing
- 2020
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Ingår i: Algal Research. - : Elsevier B.V.. - 2211-9264. ; 49
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Tidskriftsartikel (refereegranskat)abstract
- In this study the rheological properties of aqueous suspensions of three microalgae species, Nannochloropsis gaditana, Scenedesmus almeriensis and Spirulina platensis, were investigated as a function of solids content, and related to their composition and microstructure. In addition, the impact of ultrasound processing on their structuring ability was also studied. The less rigid character of the Spirulina platensis cell walls (with very low carbohydrate contents) and the presence of extracellular components promoted cell-cell interactions, yielding suspensions which showed a shear thinning behaviour at lower concentrations than Nannochloropsis gaditana and Scenedesmus almeriensis. It is noteworthy that the three species showed different viscoelastic properties at 25 wt.% total solids. Spirulina platensis suspensions showed a more elastic behaviour and lower frequency dependence, characteristic of weak gels, whilst Nannochloropsis gaditana and Scenedesmus almeriensis behaved more like viscous liquids. The ultrasound treatment did not affect the cell wall integrity, but it promoted the release of intracellular components (some of which could have been partially degraded) and disrupted physical interparticle interactions in Nannochloropsis gaditana and Scenedesmus almeriensis. This has an impact on the rheological properties, increasing the viscosity of Nannochloropsis gaditana suspensions, whilst the viscosity of Scenedesmus almeriensis suspensions was reduced. The outcomes of this work give insights into the exploitation of these microalgae species in soft materials for food, pharma and other technological applications.
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| 5. |
- Fontes-Candia, Cynthia, et al.
(författare)
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Rheological and structural characterization of carrageenan emulsion gels
- 2020
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Ingår i: Algal Research. - : Elsevier B.V.. - 2211-9264. ; 47
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Tidskriftsartikel (refereegranskat)abstract
- Carrageenan emulsion gels containing sunflower oil were prepared using three different commercial carrageenan grades (κ-C, ι-C and λ-C). The effect of the carrageenan and salt content, as well as the oil:water ratio, on the emulsion gel strength was evaluated through a response surface methodology. Moreover, the rheological properties and the micro- and nanostructure from the stronger emulsion gel formulations were investigated and compared to their analogous hydrogel formulations. Interestingly, emulsion gels formed stronger and more thermally stable networks than the hydrogels, being this effect more evident in ι-C and λ-C. The results indicate that this was mainly due to a polysaccharide concentration effect, as no evidence of interactions between the carrageenan and the oil phase was found. Consequently, the rheological behaviour of the emulsion gels was mostly determined by the type of carrageenan. The association of carrageenan molecular chains was favoured in κ-C and λ-C (due to the presence of κ-carrageenan in the latter) and promoted by the addition of KCl. In contrast, a lower degree of chain association, mostly driven by ionic cross-linking, took place in ι-C. These results evidence the relevance of the gelation mechanism on the properties of emulsion gels and provide the basis for the design of these systems for targeted applications within the food industry.
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| 6. |
- Fontes-Candia, Cynthia, et al.
(författare)
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Understanding nanostructural differences in hydrogels from commercial carrageenans: Combined small angle X-ray scattering and rheological studies
- 2020
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Ingår i: Algal Research. - : Elsevier BV. - 2211-9264. ; 47, s. 101882-
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Tidskriftsartikel (refereegranskat)abstract
- Hydrogels from commercial carrageenans (κ-C, ι-C, λ↑-C (high viscosity) and λ↓-C (low viscosity)) were prepared with and without the addition of salts (KCl and CaCl2). FT-IR and 1H NMR characterization evidenced that while the κ-C and ι-C grades were relatively pure carrageenans, the two λ-C grades were λ-, κ-, θ- and μ-carrageenan hybrids. The effect of carrageenan and salt concentration on the hydrogel strength were evaluated through a response surface design and a detailed structural characterization was carried out by small angle X-ray scattering (SAXS) and rheology. The low amount of sulphate substitution in κ-C enabled intramolecular association, giving rise to strong hydrogels, even in the absence of salts. On the other hand, ι-C, λ↑-C and λ↓-C produced much weaker hydrogels and required the addition of salts to induce intramolecular association by ionic cross-linking. SAXS results suggested the formation of similar structures of double helices in κ-C and ι-C with the addition of salts; however, distinct network structures were attained. In the case of κ-C, a Gauss-Lorentz gel model was suitable to describe the hydrogel structure and the addition of K+ promoted the formation of more ordered and densely packed structures. On the other hand, larger but weaker aggregates, with marked periodicity, were observed in ι-C, with Ca2+ inducing the formation of more densely packed networks. The complex composition of the λ-C grades gave rise to more heterogeneous branched network structures, properly described by a correlation length model, where the gelation mechanism was mostly governed by the κ-carrageenan component.
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| 7. |
- Malafronte, Loredana, 1986, et al.
(författare)
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Macroalgae suspensions prepared by physical treatments: Effect of polysaccharide composition and microstructure on the rheological properties
- 2021
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Ingår i: Food Hydrocolloids. - : Elsevier BV. - 0268-005X .- 1873-7137. ; 120
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Tidskriftsartikel (refereegranskat)abstract
- The use of macroalgae in food products is growing due to their techno-functionality and nutritional properties. In this context, an increased understanding of the rheological properties which are relevant for manufacturing and texture is needed. Here we investigated the impact of thermal and mechanical treatments, including high pressure homogenisation (HPH), on the polysaccharide composition, microstructure, and rheological properties of brown algae Laminaria digitata suspensions (5 wt %). Monosaccharide analysis and immunolabeling of alginate in combination with confocal laser scanning microscopy, revealed a sequential release of different polysaccharides as result of the applied shear. Results showed that thermal treatment (70 °C 1 h) and mild shear lead to suspensions of clusters of cells and release of fucoidan and laminarin into the liquid phase, conferring shear thinning properties to the suspensions. High pressure homogenisation was able to completely break the macroalgae cells, reducing particle size and releasing other soluble polysaccharides, in particular alginate, conferring gel properties (G'>G'') to the suspensions. This study contributes to the knowledge of how to design sustainable, innovative and nutritious liquid/semiliquid food products containing macroalgae biomass.
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| 8. |
- Martinez-Sanz, Elena, et al.
(författare)
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Minimally invasive mandibular bone augmentation using injectable hydrogels
- 2012
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Ingår i: Journal of Tissue Engineering and Regenerative Medicine. - : Hindawi Limited. - 1932-6254. ; 6:S3, s. s15-s23
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Tidskriftsartikel (refereegranskat)abstract
- Hyaluronic acid-based hydrogels are proven biocompatible materials and excellent carriers of bone morphogenetic protein-2 (BMP-2) that have been successfully tested for bone generation in vivo. Different formulations, with or without nanohydroxyapatite, have shown promise for craniofacial applications. In this study, 28 rats were used to investigate whether it is possible to achieve mandibular bone augmentation upon injection of novel hyaluronic acid-based hydrogels containing nanohydroxyapatite and different concentrations of BMP-2 (0, 5 and 150ÎŒg/ml). The biomaterials were injected subperiosteally through fine needles into the innate mandibular diastema, imitating a clinical procedure for resorbed mandibles. No incisions, flaps or sutures were necessary. After 8weeks the mandibles were evaluated by peripheral quantitative computed tomography (pQCT), micro-computed tomography (ÎŒCT), histology, immunohistochemistry and fluorochrome labelling. As a result, engineered bone was observed in all treated mandibles, with a statistically significant increase in mandibular bone volume correlated with the amount of BMP-2 loaded in the hydrogel formula. We therefore demonstrated that minimally invasive mandibular bone augmentation is possible upon injection in rats, when using the appropriate injectable scaffolds. This represents an attractive clinical alternative for oral implantology patients.
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| 9. |
- Martinez-Sanz, Marta, et al.
(författare)
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Advanced structural characterisation of agar-based hydrogels : Rheological and small angle scattering studies
- 2020
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Ingår i: Carbohydrate Polymers. - : Elsevier BV. - 0144-8617 .- 1879-1344. ; 236
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Tidskriftsartikel (refereegranskat)abstract
- Agar-based extracts from Gelidium sesquipedale were generated by heat and combined heat-sonication, with and without the application of alkali pre-treatment. Pre-treatment yielded extracts with greater agar contents; however, it produced partial degradation of the agar, reducing its molecular weight. Sonication produced extracts with lower agar contents and decreased molecular weights. A gelation mechanism is proposed based on the rheological and small angle scattering characterization of the extracts. The formation of strong hydrogels upon cooling was caused by the association of agarose chains into double helices and bundles, the sizes of which depended on the agar purity and molecular weight. These different arrangements at the molecular scale consequently affected the mechanical performance of the obtained hydrogels. Heating of the hydrogels produced a gradual disruption of the bundles; weaker or smaller bundles were formed upon subsequent cooling, suggesting that the process was not completely reversible.
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| 10. |
- Martínez-Sanz, Marta, et al.
(författare)
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Alternative protocols for the production of more sustainable agar-based extracts from Gelidium sesquipedale
- 2021
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Ingår i: Algal Research. - : Elsevier B.V.. - 2211-9264. ; 55
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Tidskriftsartikel (refereegranskat)abstract
- Agar-based extracts from Gelidium sesquipedale were obtained by applying a conventional hot water treatment and alternative ultrasound- and microwave-assisted methods, with and without the application of an alkaline pre-treatment. The alkaline pre-treatment produced refined extracts with higher purity; however, extraction yields increased from 2–5% to 7–19% by omitting this step. In particular, the ultrasound-assisted extraction allowed reducing 4-fold the extraction time, while keeping constant or even increasing the yield (up to 19% for the 1 h extraction) with respect to the conventional protocol. Interestingly, the presence of proteins and polyphenols conferred the semi-refined extracts a relatively high antioxidant capacity (19–24 μmol TE/g extract). The refined extract produced by the standard protocol formed the strongest hydrogels (>1000 g/cm2). On the other hand, the semi-refined extracts produced by the alternative protocols formed slightly stronger hydrogels (337–438 g/cm2) than the refined counterparts (224–311 g/cm2), due to their greater molecular weights of the former ones. LCA assessment showed lower global warming potential for the semi-refined extracts, especially the ultrasound-assisted extraction, hence highlighting the potential of this method to produce more sustainable agar-based extracts for food-related applications.
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