The mechanics of cell-seeded collagen hydrogels
This study aims to measure the mechanical properties, namely permeability and stiffness, of HepG2 cell-seeded collagen hydrogels. Confined compression testing in conjunction with biphasic theory modelling was utilised to provide measures of these mechanical parameters of interest. Different cell seeding densities and culture durations were tested to observe their effects on mechanical properties in order to understand how significantly the cells remodel the gel and alter mechanical properties with their physical presence. Background: Physical and mechanical interactions between cells and ECM components have been shown to affect cellular characteristics and the mechanics of the overall construct. The appropriateness of the scaffold can therefore influence cellular properties and function. Methodology: 0.3% collagen hydrogels were seeded with HepG2 cells at different seeding densities ('no cell' control, 1x10⁴, 2x10⁴, 5x10⁴, 10x10⁴ and 20x10⁴ cells/well) and cultured for durations of 1, 3 and 5 days. An MTT assay was used to determine cell viability before mechanical tests were undertaken. Confined compression in conjunction with biphasic modelling was used to determine measures for the Aggregate Modulus (HA), Hydraulic Permeability (k₀), Nonlinear Permeability Coefficient (M), Correlation Coefficient (r²), peak stress and equilibrium stress. Results and conclusions: No statistically significant trends were determined for the mechanical properties between cell seeding densities, however differences in hydraulic permeability and peak stress were observed with culture duration. r² values obtained from this study suggest experimental data analysed with the biphasic model has large confidence intervals and may not be entirely suitable.
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