Measurement of single-cell elasticity by nanodiamond-sensing of non-local deformation

TL;DR

This study introduces a nanodiamond-based method to measure non-local cell deformation, revealing the influence of capillarity and cytoskeleton on cell elasticity with high precision, bypassing the need for detailed local contact modeling.

Contribution

It presents a novel nanodiamond sensing technique to assess non-local deformation in cells, improving accuracy in cell mechanics measurement without detailed contact modeling.

Findings

Capillarity affects apparent cell elastic moduli.

Depolymerization reduces cell elasticity and surface tension.

Nanodiamond sensing enables high-precision, non-local deformation measurement.

Abstract

Nano-indentation based on, e.g., atomic force microscopy (AFM), can measure single cell elasticity with high spatial resolution and sensitivity, but relating the data to cell mechanical properties depends on modeling that requires knowledge about the local contact between the indentation tip and the material, which is unclear in most cases. Here we use the orientation sensing by nitrogen-vacancy centers in nanodiamonds to chart the non-local deformation of fixed HeLa cells induced by AFM indentation, providing data for studying cell mechanics without requiring detailed knowledge about the local contact. The competition between the elasticity and capillarity on the cells is observed. We show that the apparent elastic moduli of the cells would have been overestimated if the capillarity is not considered (as in most previous studies using local depth-loading data). We also find reduction of both elastic moduli and surface tensions due to depolymerization of the actin cytoskeleton structure. This work demonstrates that, under shallow indentation, the nanodiamond sensing of non-local deformation with nanometer precision is particularly suitable for studying mechanics of cells.