Key result
An explicit model for AFM force-indentation curves successfully extracted viscoelastic properties, showing that mitotic HeLa cells have higher apparent elasticity and lower apparent viscosity.
The proposed explicit model provides a simple method to extract viscoelastic properties of cells directly from standard AFM force-indentation curves.
Provides explicit viscoelastic model from routine AFM curves; leaves open cardiovascular cell mechanics applications pending validation.
Atomic force microscopy (AFM) is widely used for quantifying the mechanical properties of soft materials such as cells. AFM force-indentation curves are conventionally fitted with a Hertzian model to extract elastic properties. These properties solely are, however, insufficient to describe the mechanical properties of cells. Here, we expand the analysis capabilities to describe the viscoelastic behavior while using the same force-indentation curves. Our model gives an explicit relation of force and indentation and extracts physically meaningful mechanical parameters. We first validated the model on simulated force-indentation curves. Then, we applied the fitting model to the force-indentation curves of two hydrogels with different crosslinking mechanisms. Finally, we characterized HeLa cells in two cell cycle phases, interphase and mitosis, and showed that mitotic cells have a higher apparent elasticity and a lower apparent viscosity. Our study provides a simple method, which can be directly integrated into the standard AFM framework for extracting the viscoelastic properties of materials.
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Abuhattum et al. (2022) studied this question. Explicit model to extract viscoelastic properties vs. Conventional Hertzian model was evaluated on Viscoelastic properties (apparent elasticity and apparent viscosity). An explicit model for AFM force-indentation curves successfully extracted viscoelastic properties, showing that mitotic HeLa cells have higher apparent elasticity and lower apparent viscosity.
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