Atomic force microscopy-based mechanobiology

Abstract

Mechanobiology focuses on how physical forces and the mechanical properties of proteins, protein assemblies, cells and tissues contribute to signalling, development, cell division, differentiation and sorting, physiology and disease 1-4. On virtually any scale, ranging from organisms 2,4 to components such as organs 5,6 , tissues 3,7 , cells 8-10 , viruses 11,12 , complex extracellular or intracellular architecture (including vesicles, the extracellular matrix or actin network 13,14) or single proteins 15-17 , biological systems respond to mechanical forces and generate mechanical cues. In mechanobiology, living systems are described by cycles of mechanosensation, mechanotransduction and mechanoresponse 2,18. In addition to its state, the functional response of a living system depends on the nature of the mechanical signal, whether it is applied at the nanometre or micrometre scale, for a short or long time, with low or high magnitude, and on whether it is scalar or vectorial. Nanotechnological and microtechnological approaches have enabled tremendous progress in quantifying the mechanical properties of biological systems. The links between mechanical response, morphology and function, however, are conspicuously ill understood. The most widely used approaches to structurally map the mechanical properties and responses of biological systems, ranging from millimetre to sub-nanometre resolution and from micronewton to piconewton sensitivity, are based on atomic force microscopy (AFM) 19,20. In this Review, we survey the exciting developments in AFM-based approaches towards the morphological mapping of a wide variety of mechanical properties and the characterization of the functional response of biological systems under physiologically relevant conditions. We further discuss key challenges and caveats that have to be taken into account to overcome the limitations of AFM-based approaches to more fully describe the mechanical properties of living systems and highlight how complementary techniques can contribute to directly linking the functional responses of complex biological systems to mechanical cues. Characterizing biosystems by AFM The introduction of AFM in 1986 opened the door to imaging and manipulating matter at the atomic, molecular and cellular scales and was central to the nascent nanotechnological revolution 21,22. Of particular importance for the characterization of biological systems, atomic force microscopes can operate in aqueous environments and at physiological temperatures. In an atomic force microscope, a cantilever that is several micrometres long and has a molecularly sharp probe at the end is used to trace the sample topography, detecting

Cortical cell stiffness is independent of substrate mechanics

“…Error! Reference source not found. ), and it can be combined in the future with other models 36 to disentangle the contributions of the coat and the cells to the measurements.…”

Tissue rheology in embryonic organization

“…It records the bending of a cantilever with known mechanical properties that approaches and contacts the surface of a cell or tissue at a defined speed (Gautier et al, 2015;Haase & Pelling, 2015;Krieg et al, 2019). We will first introduce the different rheological states a tissue can exhibit and how these states are defined by certain tissue architecture features.…”

“…We will then summarize and discuss recent findings on the Box 1: Biophysical tools measuring embryonic tissue rheology Cell/tissue force spectroscopy: Cell/tissue force spectroscopy is an Atomic Force Microscopy (AFM) application used for measuring material properties of cells and tissues. It records the bending of a cantilever with known mechanical properties that approaches and contacts the surface of a cell or tissue at a defined speed (Gautier et al, 2015;Haase & Pelling, 2015;Krieg et al, 2019). For probing large-scale material properties within embryonic tissues, typically a large bead is attached to the AFM cantilever in order to avoid probing local cell heterogeneities.…”

Adhesion force spectroscopy with nanostructured colloidal probes reveals nanotopography-dependent early mechanotransductive interactions at the cell membrane level

“…To unravel the molecular mechanisms of cellular mechanosensing and the mechanotransductive responses it provokes in the cells, versatile biophysical approaches are essential 10,17,29,[32][33][34][35][36][37][38][39] . Smart biomaterials with complex structural architectures and/or tuneable physical properties are needed to create controllable cellular microenvironments that mimic the in vivo ECM situation 7,29,32,34,35 .…”