Creep indentation of single cells.

Area of Science:

• Biophysics
• Cell Mechanics
• Biomaterials

Background:

• Understanding the mechanical properties of individual cells is crucial for studying cellular functions and diseases.
• Existing methods often lack the precision to measure the viscoelastic behavior of single, adherent cells under controlled stress.
• Investigating mechanotransduction pathways requires precise tools to probe cell mechanics at the single-cell level.

Purpose of the Study:

• To design, develop, and validate a novel apparatus for creep indentation of individual adherent cells.
• To quantitatively measure the viscoelastic properties of single anchorage-dependent cells using stress-controlled experiments.
• To establish a new methodology for analyzing cell mechanics and mechanotransduction.

Main Methods:

• Development of a creep cytoindentation apparatus (CCA) capable of resolving forces in the nN range and deformations in the 0.1 micron range.
• Performing stress-controlled indentation experiments on single bovine articular chondrocytes with loads around 10 nN.
• Modeling the observed viscoelastic behavior using the punch problem and standard linear solid models.

Main Results:

• The CCA successfully performed stress-controlled indentation on single cells, measuring viscoelastic responses.
• Young's modulus was determined to be 1.11 +/- 0.48 kPa via the punch problem model.
• The standard linear solid model yielded an instantaneous elastic modulus of 8.00 +/- 4.41 kPa, a relaxed modulus of 1.09 +/- 0.54 kPa, apparent viscosity of 1.50 +/- 0.92 kPa-s, and a time constant of 1.32 +/- 0.65 s.

Conclusions:

• The developed creep cytoindentation apparatus (CCA) is a novel tool for single-cell mechanical characterization.
• This study presents the first stress-controlled indentation testing at the single cell level.
• The methodology provides new insights into the mechanical nature of anchorage-dependent cells and their mechanotransduction pathways.