the central goals of mechanobiology are to understand how cells generate force and how they respond to environmental mechanical stimuli. A full picture of these processes requires high-resolution, volumetric imaging with time-correlated force measurements. Here we present an instrument that combines an open-top, single-objective light sheet fluorescence microscope with an atomic force microscope (AfM), providing simultaneous volumetric imaging with high spatiotemporal resolution and high dynamic range force capability (10 pN-100 nN). With this system we have captured lysosome trafficking, vimentin nuclear caging, and actin dynamics on the order of one second per single-cell volume. to showcase the unique advantages of combining Line Bessel light sheet imaging with AfM, we measured the forces exerted by a macrophage during fcɣR-mediated phagocytosis while performing both sequential two-color, fixed plane and volumetric imaging of F-actin. This unique instrument allows for a myriad of novel studies investigating the coupling of cellular dynamics and mechanical forces. Cells interact mechanically with their environment by generating and responding to forces. A focus on the mechanical dynamics of cell phenomena such as motility, division and phagocytosis is essential for understanding stem cell fate 1 , cancer progression 2 and innate immunity 3. These mechanical processes are inherently three-dimensional (3D) and are regulated both by very local (nm) interactions as well as whole-cell scale (μm) biochemical and mechanical signaling. Obtaining a more complete picture of a cell's mechanical interaction with its environment requires monitoring local and global structures in 3D while simultaneously measuring associated forces. These goals necessitate integrating high spatial and temporal resolution volumetric imaging methods with high resolution force acquisition. Light sheet florescence microscopy (LSFM) enables acquisition of volumetric, multicolor time series at a high resolution and frame rate with low background fluorescence and low phototoxicity 4-6. Among single cell force methods 7 , Atomic Force Microscopy (AFM) 8 is unique in combining a large force range (10-11-10-6 N) that enables molecular-scale to tissue-level mechanics measurements, with high bandwidth temporal resolution (μs) and sub-nanometer spatial control. LSFM provides sufficient spatiotemporal resolution for studying cell-wide protein specific dynamics that AFM imaging cannot. Therefore, by using the AFM for force spectroscopy and LSFM for imaging we have exploited the strengths of each technique resulting in a system that is greater than its parts. Combining LSFM with AFM (AFM-LS) imposes significant geometrical constraints to the optical system design, and demands low vibration operation to accommodate sensitive force measurements. To address this challenge, we used a single-objective selective plane microscopy (soSPIM) technique integrated with, and time-synchronized to, an AFM. As described in a report on our first generation system 9 , we gene...

No abstract

The central goals of mechanobiology are to understand how cells generate force and how they respond to environmental mechanical stimuli. A full picture of these processes requires high-resolution, volumetric imaging with time-correlated force measurements. Here we present an instrument that combines an open-top, single-objective light sheet fluorescence microscope with an atomic force microscope (AFM), providing simultaneous volumetric imaging with high spatiotemporal resolution and high dynamic range force capability (10 pN – 100 nN). With this system we have captured lysosome trafficking, vimentin nuclear caging, and actin dynamics on the order of one second per volume. To showcase the unique advantages of combining Line Bessel light sheet imaging with AFM, we measured the forces exerted by a macrophage during FcɣR-mediated phagocytosis while performing both sequential two-color, fixed plane and volumetric imaging of F-actin. This unique instrument allows for a myriad of novel studies investigating the coupling of cellular dynamics and mechanical forces.

Changes in cellular mechanical properties correlate with the progression of metastatic cancer along the epithelial-to-mesenchymal transition (EMT). Few high-throughput methodologies exist that measure cell compliance, which can be used to understand the impact of genetic alterations or to screen the efficacy of chemotherapeutic agents. We have developed a novel array high-throughput microscope (AHTM) system that combines the convenience of the standard 96-well plate with the ability to image cultured cells and membrane-bound microbeads in twelve independently-focusing channels simultaneously, visiting all wells in eight steps. We use the AHTM and passive bead rheology techniques to determine the relative compliance of human pancreatic ductal epithelial (HPDE) cells, h-TERT transformed HPDE cells (HPNE), and four gain-of-function constructs related to EMT. The AHTM found HPNE, H-ras, Myr-AKT, and Bcl2 transfected cells more compliant relative to controls, consistent with parallel tests using atomic force microscopy and invasion assays, proving the AHTM capable of screening for changes in mechanical phenotype.