New hydrogels based on the interpenetration of physical gels of agarose and chemical gels of polyacrylamide

Fernández, Emiliano Fernández de Pinedo y; Mijangos, Carmen; Guenet, Jean‐Michel; Cuberes, M. Teresa; López, Daniel

doi:10.1016/j.eurpolymj.2008.11.041

Cited by 16 publications

(12 citation statements)

References 35 publications

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“…Nevertheless, this difficulty seems to be reduced by the use of microcalorimetry. In this way, similar results were obtained by performing this type of measurement on gels with low PVA concentrations,(8) although the uncertainties related to the obtained results are still large.…”

Section: Resultssupporting

confidence: 82%

“…8,33 If covalent cross-links were an important contribution to the final gel properties, then residual couplings should persist even above the melting temperature of the crystallites, which is not the case. However, the presence of (rapidly tumbling) microgels above the main melting point cannot be ruled out and is in fact indicated by the relatively high viscosity (as checked by a simple tilt test).…”

Section: Resultsmentioning

confidence: 99%

“…The cross-link points are therefore constituted of polymer crystallites, and the formed gels could be described by a bicontinuous structure of polymer-rich and polymer-poor regions. In contrast, Hernández et al, 8−10 on the basis of DSC measurements, also inferred the possibility of the existence of covalent cross-links between the polymer chains brought about by the formation of radicals due to strong local shear during water crystal growth. (33)…”

Section: Introductionmentioning

confidence: 97%

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Structure of Poly(vinyl alcohol) Cryo-Hydrogels as Studied by Proton Low-Field NMR Spectroscopy

et al. 2008

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The network structure of poly(vinyl alcohol) (PVA) hydrogels obtained by freezing−thawing cycles was investigated by solid-state 1H low-field NMR spectroscopy. By the application of multiple-quantum NMR experiments, we obtain information about the segmental order parameter, which is directly related to the restrictions on chain motion (cross-links) formed upon gelation. These measurements indicate that the network mesh size as well as the relative amount of nonelastic defects (i.e., non-cross-linked chains, dangling chains, loops) decrease with the number of freezing−thawing cycles but are independent of the polymer concentration. The formation of the PVA network is accompanied by an increasing fraction of polymer with fast magnetization decay (∼20 μs). The quantitative study of this rigid phase with a specific refocusing pulse sequence shows that it is composed of a primary crystalline polymer phase (∼5%), which constitutes the main support of the network structure and determines the mesh size, and a secondary population of more imperfect crystallites, which increase the number of elastic chain segments in the polymer gel but do not affect the average network mesh size appreciably. Correspondingly, progressive melting of the secondary crystallites with increasing temperature does not affect the network mesh size but only the amount of network defects, and melting of the main PVA crystallites at ∼80 °C leads to the destruction of the network gel and the formation of an isotropic PVA solution.

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Section: Resultssupporting

confidence: 82%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 97%

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Structure of Poly(vinyl alcohol) Cryo-Hydrogels as Studied by Proton Low-Field NMR Spectroscopy

et al. 2008

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“…Lower concentrations than generally reported were tested (0.25 to 0.6 %) and measured μ ∞ were over a lower range (0.07 to 1.8 kPa for ν=0.35 – 0.499) than previously reported. For the 0.5 % agarose hydrogel, the estimated value of μ ∞ (1.1 ± 0.33 kPa for ν= 0.499) was similar to that found previously by Fernandez et al (μ ∞ ~ 1.3 kPa) under low frequency (1 Hz) tensional shear testing 34 and by Normand et al (μ ∞ ~ 1.8 kPa) under compression testing of low viscous agarose gels 35 (we compared values for ν=0.499 since previous mechanical testing studies assumed material incompressibility). Our estimated value was also similar to the modulus moduli measured by Yang et al using a similar OCT-indentation system (μ ∞ ~ 0.8 kPa estimated from their displacement curve using our Abacus model) 27 .…”

Section: Discussionsupporting

confidence: 88%

Optically based‐indentation technique for acute rat brain tissue slices and thin biomaterials

et al. 2011

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Currently, micro-indentation testing of soft biological materials is limited in its capability to test over long time scales due to accumulated instrumental drift errors. As a result, there is a paucity of measures for mechanical properties such as the equilibrium modulus. In this study, indentation combined with optical coherence tomography (OCT) was used for mechanical testing of thin tissue slices. OCT was used to measure the surface deformation profiles by placing spherical beads onto submerged test samples. Agarose-based hydrogels at low-concentrations (w/v, 0.3–0.6 %) and acute rat brain tissue slices were tested using this technique over a 30 min time window. To establish that tissue slices maintained cell viability, allowable testing times were determined by measuring neuronal death or degeneration as a function of incubation time with Fluor-Jade C (FJC) staining. Since large deformations at equilibrium were measured, displacements of surface beads were compared with finite element elastic contact simulations to predict the equilibrium modulus, μ∞. Values of μ∞ for the low- concentration hydrogels ranged from 0.07–1.8 kPa, and μ∞ for acute rat brain tissue slices was 0.13 ± 0.04 kPa for the cortex and 0.09 ± 0.015 kPa for the hippocampus (for Poisson ratio=0.35). This indentation technique offers a localized, real-time, and high resolution method for long-time scale mechanical testing of very soft materials. This test method may also be adapted for viscoelasticity, for testing of different tissues and biomaterials, and for analyzing changes in internal structures with loading.

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“…The precipitate was rinsed with deionized water three times to remove ammonium nitrate and excess ammonium hydroxide. The sample is then quenched in liquid nitrogen and freeze‐dried for 2 d to obtain agarose/zirconia nanocomposite . Zirconia precipitation in the absence of agarose was also carried out as a benchmark for comparison.…”

Section: Methodsmentioning

confidence: 99%

Aqueous Route Synthesis of Mesoporous ZrO₂ by Agarose Templation

Klosterman

et al. 2012

J. Am. Ceram. Soc.

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Mesoporous zirconia with high surface area has been synthesized using self‐assembling agarose gel as a template. Agarose gel was formed in the presence of aqueous zirconyl nitrate solutions followed by precipitation of zirconium (hydr)oxide in the gel framework. A porous zirconia structure is obtained by pyrolysis of agarose. Fourier transform infrared spectroscopy is employed to assess the agarose‐zirconia precursor interaction. Changes in the C–O absorption bands indicate zirconium association with the OH groups of the agarose. Solid state 13C NMR studies of the nanocomposite showed a shift in intensity from 70 to 75 ppm indicating conversion of ~7% of C–O–H to C–O–Zr. Scanning electron microscopy reveals that both agarose/zirconia nanocomposite and zirconia have similar morphological features as that of pure agarose gel confirming agarose templation. Phase transformation of zirconia from amorphous to tetragonal between 300°C and 500°C, and gradually into monoclinic phase up to 900°C is observed using X‐ray powder diffraction. Specific surface area and pore size distribution are determined using nitrogen adsorption, employing BET and Barrett–Joyner–Halenda methods, respectively. The specific surface area of porous zirconia after heat treatment at 500°C was determined to be 86 m2/g, which reduced with increasing temperature to 13 m2/g above 900°C. Transmission electron microscopy confirmed the hierarchical structure of porous zirconia.

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New hydrogels based on the interpenetration of physical gels of agarose and chemical gels of polyacrylamide

Abstract: In this paper we report a novel method for preparing interpenetrating polymer hydrogels of agarose and polyacrylamide (PAAm)

Cited by 16 publications

References 35 publications

Structure of Poly(vinyl alcohol) Cryo-Hydrogels as Studied by Proton Low-Field NMR Spectroscopy

Structure of Poly(vinyl alcohol) Cryo-Hydrogels as Studied by Proton Low-Field NMR Spectroscopy

Optically based‐indentation technique for acute rat brain tissue slices and thin biomaterials

Aqueous Route Synthesis of Mesoporous ZrO₂ by Agarose Templation

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New hydrogels based on the interpenetration of physical gels of agarose and chemical gels of polyacrylamide

Abstract: In this paper we report a novel method for preparing interpenetrating polymer hydrogels of agarose and polyacrylamide (PAAm)

Cited by 16 publications

References 35 publications

Structure of Poly(vinyl alcohol) Cryo-Hydrogels as Studied by Proton Low-Field NMR Spectroscopy

Structure of Poly(vinyl alcohol) Cryo-Hydrogels as Studied by Proton Low-Field NMR Spectroscopy

Optically based‐indentation technique for acute rat brain tissue slices and thin biomaterials

Aqueous Route Synthesis of Mesoporous ZrO2 by Agarose Templation

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Aqueous Route Synthesis of Mesoporous ZrO₂ by Agarose Templation