Atomic force microscopy-based mechanobiology

Mechanobiology emerges at the crossroads of medicine, biology, biophysics and engineering and describes how the responses of proteins, cells, tissues and organs to mechanical cues contribute to development, differentiation, physiology and disease. The grand challenge in mechanobiology is to quantify how biological systems sense, transduce, respond and apply mechanical signals. Over the past three decades, atomic force microscopy (AFM) has emerged as a key platform enabling the simultaneous morphological and mechanical characterization of living biological systems. In this Review, we survey the basic principles, advantages and limitations of the most common AFM modalities used to map the dynamic mechanical properties of complex biological samples to their morphology. We discuss how mechanical properties can be directly linked to function, which has remained a poorly addressed issue. We outline the potential of combining AFM with complementary techniques, including optical microscopy and spectroscopy of mechanosensitive fluorescent constructs, super-resolution microscopy, the patch clamp technique and the use of microstructured and fluidic devices to characterize the 3D distribution of mechanical responses within biological systems and to track their morphology and functional state. Mechanobiology describes how biological systems respond to mechanical stimuli. This Review surveys basic principles, advantages and limitations of applying and combining atomic force microscopy-based modalities with complementary techniques to characterize the morphology, mechanical properties and functional response of complex biological systems to mechanical cues. Key points The versatile functions of biological systems ranging from molecules, cells and cellular systems to living organisms are governed by their mechanical properties and ability to sense mechanical cues and respond to them. Atomic force microscopy (AFM)-based approaches provide multifunctional nanotools to measure a wide variety of mechanical properties of living systems and to apply to them well-defined mechanical cues. AFM allows us to apply and measure forces from the piconewton to the micronewton range on spatially defined areas with sizes ranging from the sub-nanometre to several tens of micrometres. Mechanical parameters characterized by AFM include force, pressure, tension, adhesion, friction, elasticity, viscosity and energy dissipation. The mechanical parameters of complex biological systems can be stru