Microrheology of cells with magnetic force modulation atomic force microscopy

Area of Science:

• Biophysics
• Cell Mechanics
• Materials Science

Background:

• Atomic Force Microscopy (AFM) is a powerful tool for probing cellular mechanical properties.
• Existing AFM methods may have limitations in measuring dynamic viscoelastic properties of living cells.
• Understanding cell mechanics is crucial for various biological processes and disease states.

Purpose of the Study:

• To develop and validate a novel magnetic force modulation method for measuring cell stiffness and viscosity.
• To apply this method to determine the frequency-dependent stiffness and internal friction of 3T3 fibroblasts.
• To compare experimental results with established rheological models.

Main Methods:

• Utilized a modified AFM apparatus with a magnetic cantilever.
• Applied an oscillating magnetic field to induce AC indentation on living cells.
• Compared cantilever motion amplitudes (free vs. sample contact) to calculate mechanical properties.

Main Results:

• Determined the frequency-dependent stiffness of 3T3 fibroblasts using a power law: k(s)(f) = α + β(f/f¯)(γ) with γ = 0.6.
• The obtained stiffness coefficient (γ) aligns well with rheological data from actin solutions.
• Estimated an average damping coefficient of 75.1 μN s m(-1) for cells at specific indentation depths.

Conclusions:

• The magnetic force modulation method provides a reliable approach for quantifying cell viscoelasticity.
• This technique offers insights into the internal friction and mechanical behavior of living cells.
• The findings contribute to a better understanding of cellular biomechanics and material properties.