Strain Hardening in Highly Acetylated Chitosan Gels

Furlani, Franco; Marfoglia, Andrea; Marsich, Eleonora; Donati, Ivan; Sacco, Pasquale

doi:10.1021/acs.biomac.1c00293

Cited by 17 publications

(14 citation statements)

References 39 publications

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“…Following a previously described technique, sample ACh1 was used to prepare genipin-based hydrogels [ 22 ]. The gelation kinetics were monitored in the rheometer for three hours.…”

Section: Resultsmentioning

confidence: 99%

“…Interestingly, the magnitude of strain hardening, calculated as

(see Equation (4)), scaled with the chitosan concentration ( Figure 2 ). This behavior can be safely ascribed to the formation of more physical entanglements throughout the network due to the higher flexibility of the polymer chains, i.e., an increased R D/G [ 22 ].…”

Section: Resultsmentioning

confidence: 99%

“…Entanglements between the polysaccharide chains are described as temporary crosslinks which are formed when the critical strain is exceeded, leading to strain hardening. This model was developed by incubating the hydrogel at 60 °C [ 22 ]. Based on the results of this study, strain hardening could be the result of an equilibrium between two phenomena: (i) the probability of temporary entanglement between the polymer chains in the forming gel; (ii) the reaction rate of genipin.…”

Section: Resultsmentioning

confidence: 99%

“…However, there are few examples of genipin–chitosan hydrogels prepared at a neutral pH. Recently, our research group has shown that highly acetylated chitosan samples are suitable for this purpose and that the hydrogels prepared exhibit a strain-hardening effect [ 22 ].…”

Section: Introductionmentioning

confidence: 99%

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Influence of Temperature and Polymer Concentration on the Nonlinear Response of Highly Acetylated Chitosan–Genipin Hydrogels

Mio

Sacco

Donati

2022

Gels

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Strain hardening, i.e., the nonlinear elastic response of materials under load, is a physiological response of biological tissues to mechanical stimulation. It has recently been shown to play a central role in regulating cell fate. In this paper, we investigate the effect of temperature and polymer concentrations on the strain hardening of covalent hydrogels composed of pH-neutral soluble chitosans crosslinked with genipin. A series of highly acetylated chitosans with a fraction of acetylated units, FA, in the range of 0.4–0.6 was synthesized by the homogeneous re-N-acetylation of a partially acetylated chitosan or the heterogeneous deacetylation of chitin. A chitosan sample with an FA = 0.44 was used to prepare hydrogels with genipin as a crosslinker at a neutral pH. Time and frequency sweep experiments were then performed to obtain information on the gelling kinetics and mechanical response of the resulting hydrogels under small amplitude oscillatory shear. While the shear modulus depends on the chitosan concentration and is almost independent of the gel temperature, we show that the extent of hardening can be modulated when the gelling temperature is varied and is almost independent of the experimental conditions used to build the hydrogels (ex situ or in situ gelation). The overall effect is attributed to a subtle balance between the physical (weak) entanglements and covalent (strong) crosslinks that determine the mechanical response of highly acetylated chitosan hydrogels at large deformations.

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“…Following a previously described technique, sample ACh1 was used to prepare genipin-based hydrogels [ 22 ]. The gelation kinetics were monitored in the rheometer for three hours.…”

Section: Resultsmentioning

confidence: 99%

“…Interestingly, the magnitude of strain hardening, calculated as

Section: Resultsmentioning

confidence: 99%

Section: Resultsmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Influence of Temperature and Polymer Concentration on the Nonlinear Response of Highly Acetylated Chitosan–Genipin Hydrogels

Mio

Sacco

Donati

2022

Gels

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“…Rheological time sweep experiments are frequently used in the characterization of viscoelastic materials to extrapolate information about their mechanical response under oscillatory stimulation [ 37 , 38 ].…”

Section: Resultsmentioning

confidence: 99%

Effect of α-Amylase on the Structure of Chia Seed Mucilage

et al. 2022

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Thanks to its nutritional and mechanical properties, chia seed mucilage is becoming increasingly popular in the food industry as a small biomolecule. The mechanical properties of an ingredient are a key element for food appreciation during chewing. Therefore, with this study, we explore for the first time the structural changes that chia seed mucilage undergoes when treated with α-amylase, the most abundant enzyme in human saliva. First, rheological time-sweep tests were performed on samples with different enzyme and constant chia mucilage concentrations. Then, the effect of increasing the chia mucilage concentration at a constant enzyme content was investigated. The results show that structural changes occur after enzyme treatment. Rheological measurements show a thickening of the material with an increase in the elastic modulus depending on the concentrations of α-amylase and chia used. This effect is attributed to the release and aggregation of insoluble fibrous aggregates that naturally form the mucilage after the cleavage of the α-1,4-glucoside bond between the α-D-glucopyranose residue and the second β-D-xylopyranose residue by α-amylase. Thus, our data suggest an α-amylase-mediated restructuring of the chia mucilage network that could have implications for the commercial processing of this material.

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Properties of Cross‐Linked Poly‐l‐lysine Hydrogels across the Random Coil–Helix Transition

Wilcox,

Grinevich,

Linscott

et al. 2023

Macro Chemistry & Physics

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Hydrogels are key components of biological tissues and have applications in biomedicine and commercial industry. Many biological tissues are known to strain harden due to the semiflexible nature of the chains. Here, the mechancial properties of poly‐l‐lysine (PLL) hydrogels, whose network chains undergo a random coil–helix transition, are studied as a function of the polypeptide's structural changes. PLL is cross‐linked with poly(ethylene glycol)diglycidyl ether at cross‐link percents ranging from 3% to 6%. The conformation change and mechanical properties are investigated with circular dichroism and small and large amplitude oscillatory shear rheology, respectively. As a function of pH at low cross‐link percents, a transition from strain softening to strain hardening is observed as the network chains become helical that is similar to the behavior of biological filamentous gels and consistent with recent theoretical descriptions of network strain hardening. At higher cross‐link densities, the hydrogels become brittle due to stress concentration in inhomogeneous locations in the network, which is studied with dynamic light scattering. Overall, the random coil–helix transition has a significant effect on the nonlinear mechanical properties of PLL hydrogels. By understanding the hydrogel structure and response to environmental changes, their potential can be expanded as functional biomedical materials.

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Strain Hardening in Highly Acetylated Chitosan Gels

Cited by 17 publications

References 39 publications

Influence of Temperature and Polymer Concentration on the Nonlinear Response of Highly Acetylated Chitosan–Genipin Hydrogels

Influence of Temperature and Polymer Concentration on the Nonlinear Response of Highly Acetylated Chitosan–Genipin Hydrogels

Effect of α-Amylase on the Structure of Chia Seed Mucilage

Properties of Cross‐Linked Poly‐l‐lysine Hydrogels across the Random Coil–Helix Transition

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