Indenting soft samples (hydrogels and cells) with cantilevers possessing various shapes of probing tip

Abstract

The identification of cancer-related changes in cells and tissues based on the measurements of elastic properties using atomic force microscopy (AFM) seems to be approaching clinical application. Several limiting aspects have already been discussed; however, still, no data have shown how specific AFM probe geometries are related to the biomechanical evaluation of cancer cells. Here, we analyze and compare the nanomechanical results of mechanically homogenous polyacrylamide gels and heterogeneous bladder cancer cells measured using AFM probes of various tip geometry, including symmetric and non-symmetric pyramids and a sphere. Our observations show large modulus variability aligned with both types of AFM probes used and with the internal structure of the cells. Altogether, these results demonstrate that it is possible to differentiate between compliant and rigid samples of kPa elasticity; however, simultaneously, they highlight the strong need for standardized protocols for AFM-based elasticity measurements if applied in clinical practice including the use of a single type of AFM cantilever.

Characterization of the nanomechanical properties of the fission yeast (Schizosaccharomyces pombe) cell surface by atomic force microscopy

“…Young’s elasticity moduli were calculated from AFM extension curves by the Asylum Igor Pro MFP-3D software using the Hertz model equation (Ahmed Touhami, Nysten, & Dufrêne, 2003; Zemła et al, 2020): Where F is the applied force, δ is the resulting indentation depth, E is the Young’s modulus, and θ is the half-opening angle (35° from manufacturer). Notably, we utilized a sample Poisson of 0.03 in these calculations as this value was utilized in prior S. pombe elasticity modeling (Abenza et al, 2015; Atilgan et al, 2015; Davi et al, 2018).…”

“…Young's elasticity moduli were calculated from AFM extension curves by the Asylum Igor Pro MFP-3D software using the Hertz model equation (Ahmed Touhami, Nysten, & Dufrêne, 2003;Zemła et al, 2020):…”

Characterization of the nanomechanical properties of the fission yeast (Schizosaccharomyces pombe) cell surface by atomic force microscopy

“…Young's elasticity moduli were calculated from AFM extension curves by the Asylum Igor Pro MFP‐3D software using the Hertz model equation (Touhami et al, 2003; Zemła et al, 2020): where F is the applied force, δ is the resulting indentation depth, E is the Young's modulus, and θ is the half‐opening angle (35° from manufacturer) (Figure S2). Notably, we used a sample Poisson of 0.03 in these calculations as this value was utilized in prior S. pombe elasticity modeling (Abenza et al, 2015; Atilgan et al, 2015; Davi et al, 2018).…”

Changes in Biomechanical Properties of A375 Cells Due to the Silencing of TMSB4X Expression Are Not Directly Correlated with Alterations in Their Stemness Features

“…We could have decided to perform experiments at the cell periphery. However, according to the literature, the outcomes obtained for that area of a cell could be adulterated by the proximity of the cantilever tip to the substrate on which cells grow [ 47 , 48 ]. That’s why we have chosen the nuclear region of the cells to perform this analysis.…”