Subsurface Imaging of Cell Organelles by Force Microscopy

Abstract

The development of high-resolution, label-free, noninvasive, and subsurface microscopy methods of living cells remains a formidable problem. Force-microscopy-based stiffness measurements contribute to our understanding of single-cell nanomechanics. The elastic properties of the cell’s outer structures, such as the plasma membrane and actin cytoskeleton, dominate stiffness measurements, which in turns prevents the imaging of intracellular structures. We propose that the above limitation could be overcome by combining 2D sections of the cell’s viscoelastic properties. We show the simultaneous imaging of the outer cell’s cytoskeleton and the organelles inside the nucleus. The elastic component of interaction force carries information on the cell’s outer elements as the cortex and the actin cytoskeleton. The inelastic component is sensitive to the hydrodynamic drag of the inner structures such the nucleoli.

Label‐Free Imaging of Cholesterol Assemblies Reveals Hidden Nanomechanics of Breast Cancer Cells

“…To tackle this point, we used an AFM-based vertical segmentation approach on living cells, which enables us to isolate the contribution of the PM from overall cell mechanics ( Figure 2g). [32,42,43] We first extracted FD curves from the nuclear region of MCF10 cells probed with a bare AFM tip. Next, we defined different fit ranges in the contact region of these FD curves to specifically extract PM and cell cortex elasticity (Figure 2g and the Experimental Section).…”

Extracting viscoelastic material parameters using an atomic force microscope and static force spectroscopy

“…Modern AFM applications commonly involve testing samples that are soft, biological, or polymeric in nature. Understanding the dissipative nature of these materials at the nanoscale is especially important to their use in many applications [1][2][3][4][5][6]. Howev-er, performing such measurements using AFM has been difficult due to the complexity of material phenomena that govern AFM observables.…”

Cells nanomechanics by atomic force microscopy: focus on interactions at nanoscale

“…Contrast by stiffness tomography was used to visualize and obtain mechanical feedback about mitochondria and Golgi apparatus without specific staining [53]. Rheological model was applied on stiffness tomography for fibroblast cells localizing actin bundle fibers under cell surface or nucleoli within nucleus structure from the contrast of different hydrodynamic drag [54]. This interesting approach can visualize mechanical properties of materials with different phases at micro-nano level even at ultralow stiffness [55], still the mathematical interpretation is ill-defined, in fact, the convolution of elastic response of different phases must be considered for a correct quantification [28].…”

“…Actin stress fibres at cell periphery and nuclear region can be easily detected from topography. Mechanical features at subcellular level in heterogenous cells can be resolved and different mechanical properties can be distinguished and quantified [54]. For example, applying small forces, the surface structure of living kidney cells were observed evidencing microvilli consisting in plasma membrane-covered actin bundles stabilized by crosslinking proteins [112].…”