Mechanical and diffusive properties of homogeneous alginate gels in form of particles and cylinders

Pasut, E.; Toffanin, Renato; Voinovich, Dario; Pedersini, Cristiano; Murano, Erminio; Grassi, Mario

doi:10.1002/jbm.a.31680

Cited by 27 publications

(13 citation statements)

References 28 publications

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“…where R is the universal gas constant, T is the temperature and G (shear modulus) can be computed as the sum of the elastic contributions (G i ) pertaining to each element of the generalized Maxwell model describing the hydrogel mechanical spectrum [35]. Finally, the equivalent network theory (see Equation (4)) [36] allows evaluating the average network mesh size !…”

Section: Rheological Characterizationmentioning

confidence: 99%

Guar gum/borax hydrogel: Rheological, low field NMR and release characterizations

Coviello¹,

Matricardi²,

Alhaique³

et al. 2013

Express Polym. Lett.

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Abstract. Guar gum (GG) and Guar gum/borax (GGb) hydrogels are studied by means of rheology, Low Field Nuclear Magnetic Resonance (LF NMR) and model drug release tests. These three approaches are used to estimate the mesh size (!) of the polymeric network. A comparison with similar Scleroglucan systems is carried out. In the case of GGb, the rheological and Low Field NMR estimations of ! lead to comparable results, while the drug release approach seems to underestimate !. Such discrepancy is attributed to the viscous effect of some polymeric chains that, although bound to the network to one end, can freely fluctuate among meshes. The viscous drag exerted by these chains slows down drug diffusion through the polymeric network. A proof for this hypothesis is given by the case of Scleroglucan gel, where the viscous contribution is not so significant and a good agreement between the rheological and release test approaches was found. Vol.7, No.9 (2013) 733-746 Available online at www.expresspolymlett.com DOI: 10.3144/expresspolymlett.2013.71 * Corresponding author, e-mail: mariog@dicamp.univ.trieste.it © BME-PT mation in aqueous solution and a single coiled disordered conformation in methylsulphoxide or at high pH values (NaOH$>0.2 M) [10,11]. Due to its peculiar properties, SCLG was extensively used for various commercial applications (secondary oil recovery, ceramic glazes, food, paints, cosmetics, etc.) [12] and it was also investigated for modified/ sustained release formulations and ophthalmic preparations [13]. Actually, it is well known that borax is an efficient crosslinker for polymers bearing hydroxyl groups but the type of formed linkages is still debated and so far two main models have been proposed. The most popular one implies the existence of pure chemical crosslinks between the polymeric chains and borax [14], and it was proposed for the GG/ borax interactions. According to the other model, the borax ions hold together the polymeric chains by means of mixed physical/chemical linkages. This model was firstly proposed for poly-(vinylalcohol) [15] and it was recently suggested also for SCLG [16,17]. The considerable effort devoted to the study of polymer-ion complexes is due to the wide range of application of these systems. In particular, the complex between GG and borate was previously studied by several authors [18,19] that investigated the effect of polymer and borate concentration, temperature, environmental pH conditions, and GG molecular weight on the peculiar rheological properties detected by the frequency dependence of relaxation spectra. Furthermore, a detailed study of the crosslinking reaction of borate ion with polyhydroxy polymers was carried out by means of 11 Keywords: polymer gels, rheology, low field NMR, transport processes, mesh-size eXPRESS Polymer Letters

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Section: Rheological Characterizationmentioning

confidence: 99%

Guar gum/borax hydrogel: Rheological, low field NMR and release characterizations

Coviello¹,

Matricardi²,

Alhaique³

et al. 2013

Express Polym. Lett.

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“…Assuming an affine tetra‐functional network, the revised Flory's theory enables the determination of polymeric network crosslink density ρ x (defined as the moles of junctions between different polymeric chains per hydrogel unit volume):

ρ_{x} = G / R T

where R is the universal gas constant, T is the temperature, and G (shear modulus) can be computed as the sum of the elastic contributions ( G i ) related to each element of the generalized Maxwell model describing the hydrogel mechanical spectrum . Equation implicitly implies that the rheological characterization is performed on a gel that did not undergo neither swelling nor deswelling with respect to the crosslinking conditions.…”

Section: Methodsmentioning

confidence: 99%

Influence of borate amount on the swelling and rheological properties of the Scleroglucan/borax system

Coviello

Margheritelli

Matricardi

et al. 2015

J of Applied Polymer Sci

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Scleroglucan is a fungal polysaccharide that, when dispersed in water, assumes a very stable triple helix structure. It has numerous industrial applications in different fields, such as food industry, cosmetics, and pharmaceutics. In the presence of borate ions, this polymer forms weak gels that, after freeze-drying and compaction, show an anisotropic swelling behavior, related to the borate/polymer ratio. By monitoring the evolution of the elastic and viscous moduli it was possible to follow the gel formation kinetics. The rheological properties of the network were studied as a function of crosslinking agent concentration and the corresponding flow curves and mechanical spectra were recorded. The kinetics of the crosslinking reaction was monitored by following the time evolution of the storage and loss moduli, after the addition of borate ions to the Scleroglucan system. Creep-recovery experiments allowed acquiring recoverable strain values and those of the critical stress above which a very high compliance of the sample is reached. Obtained results are to be related to the specific type of bonds between the polysaccharide chains and the crosslinking agent.

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“…The stiffness of a gel bead was evaluated by measuring elastic modulus of a cylindrical gel prepared with the same composition (Pasut et al, 2008). To prepare the cylindrical gel, alginate or MA solution was placed inside a plastic syringe with a diameter of 7 mm.…”

Section: Methodsmentioning

confidence: 99%

Tuning structural durability of yeast‐encapsulating alginate gel beads with interpenetrating networks for sustained bioethanol production

Cha¹,

Kim²,

Liu³

et al. 2011

Biotech & Bioengineering

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Microorganisms have become key components in many biotechnological processes to produce various chemicals and biofuels. The encapsulation of microbial cells in calcium cross-linked alginate gel beads has been extensively studied due to several advantages over using free cells. However, industrial use of alginate gel beads has been hampered by the low structural stability of the beads. In this study, we demonstrate that the incorporation of interpenetrating covalent cross-links in an ionically cross-linked alginate gel bead significantly enhances the bead's structural durability. The interpenetrating network (IPN) was prepared by first cross-linking alginate chemically modified with methacrylic groups, termed methacrylic alginate (MA), with calcium ions and subsequently conducting a photo cross-linking reaction. The resulting methacrylic alginate gel beads (IPN-MA) exhibited higher stiffness, ultimate strength and ultimate strain and also remained more stable in media either subjected to high shear or supplemented with chelating agents than calcium cross-linked alginate gel beads. Furthermore, yeast cells encapsulated in IPN-MA gel beads remained more metabolically active in ethanol production than those in calcium cross-linked alginate gel beads. Overall, the results of this study will be highly useful in designing encapsulation devices with improved structural durability for a broad array of prokaryotic and eukaryotic cells used in biochemical and industrial processes.

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Mechanical and diffusive properties of homogeneous alginate gels in form of particles and cylinders

Cited by 27 publications

References 28 publications

Guar gum/borax hydrogel: Rheological, low field NMR and release characterizations

Guar gum/borax hydrogel: Rheological, low field NMR and release characterizations

Influence of borate amount on the swelling and rheological properties of the Scleroglucan/borax system

Tuning structural durability of yeast‐encapsulating alginate gel beads with interpenetrating networks for sustained bioethanol production

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