Micromechanical model of biphasic biomaterials with internal adhesion: Application to nanocellulose hydrogel composites

[Display omitted] The mechanical properties of hydrated biomaterials are non-recoverable upon unconfined compression if adhesion occurs between the structural components in the material upon fluid loss and apparent plastic behaviour. We explore these micromechanical phenomena by introducing an aggre...

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Bibliographic Details
Published in:Acta biomaterialia 2016-01, Vol.29, p.149-160
Main Authors: Bonilla, Mauricio R., Lopez-Sanchez, P., Gidley, M.J., Stokes, J.R.
Format: Article
Language:English
Subjects:
Agglomeration
Bacteria
Biomaterials
Biomedical materials
Biphasic model
Cellulose
Composites
Compressing
Compression
Compressive Strength
Gel
Hydrogels
Hydrogels - chemistry
Mathematical models
Models, Chemical
Nanocomposites - chemistry
Poroelastic
Rheology
Surgical implants
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Summary:[Display omitted] The mechanical properties of hydrated biomaterials are non-recoverable upon unconfined compression if adhesion occurs between the structural components in the material upon fluid loss and apparent plastic behaviour. We explore these micromechanical phenomena by introducing an aggregation force and a critical yield pressure into the constitutive biphasic formulation for transversely isotropic tissues. The underlying hypothesis is that continual fluid pressure build-up during compression temporarily supresses aggregation. Once compression stops and the pressure falls below some critical value, internal aggregation occurs over a time scale comparable to the poroelastic time. We demonstrate this model by predicting the mechanical response of bacterial nanocellulose hydrogel composites, which are promising biomaterials and a structural mimetic for the plant cell wall. Cross-linking of cellulose by xyloglucan creates an extensional resistance and substantially increases the compressive modulus under large compression and densification. In comparison, incorporating non-crosslinking arabinoxylan into the hydrogel has little effect on its mechanics at the strain rates investigated. These results assist in elucidating the mechanical role of these polysaccharides in the complex plant cell wall structure. They also suggest xyloglucan is a suitable candidate to tailor the stiffness of nanocellulose hydrogels in biomaterial design, which includes modulating cell-adhesion in tissue engineering applications. The model and overall approach may be utilised to characterise and design a myriad of biomaterials and mammalian tissues, particularly those with a fibrillar structure. The mechanical properties of hydrated biomaterials can be non-recoverable upon compression due to increased adhesion occurring between the structural components in the material. Cellulose–hemicellulose composite hydrogels constitute a classical example of this phenomenon, since fibres can freely re-orient and adhere upon fluid loss to produce significant variations in the mechanical response to compression. Here, we model their micromechanics by introducing an aggregation force and a critical yield pressure into the constitutive formulation for transversely isotropic biphasic materials. The resulting model is easy to implement for routine characterization of this type of hydrated biomaterials through unconfined compression testing and produces physically meaningful and reproducible me
ISSN:1742-7061
1878-7568
DOI:10.1016/j.actbio.2015.10.032