White Paper: Collagen fibrils imaging in air and in liquid
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CORPORATE PARTNER WHITE PAPER
Collagen fibrils imaging in air and in liquid PARK SYSTEMS Mina Hong, Gerald Pascual, Byong Kim, and Keibock Lee
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s the most abundant (25–35%) protein in mammals,1 collagen is found everywhere in connective tissues, including bone, skin, and muscle. Thus characterization of the structure, compositions, and mechanical properties of collagen fibrils is crucial in understanding their performance over time. Atomic force microscopy (AFM), as a powerful nanotechnology tool, has been widely used to determine the morphology, mechanical properties, and in situ self-assembly processes of collagen fibrils.2 Conventional techniques to characterize these collagen fibrils are mainly based on AFM force-volume spectroscopy, which collects force– distance (F–d) curves at each pixel to calculate material properties. However, these techniques have been recognized as being exceedingly slow—it takes hours to acquire an elasticity map. Driven by the demand for a much faster technique, Park Systems developed the PinPoint Nanomechanical Mode to provide a solution that is at least 100 times faster than traditional techniques.3 With this application, an elasticity map can be acquired within minutes and with a correlated topography image that reveals the position and orientation of the sample. This mode represents a new application tool for acquiring real-time topography and quantitative mechanical property maps of various materials, ranging from hard disks to soft tissues. Here, we report imaging collagen fibrils using the PinPoint Nanomechanical Mode. Park Systems The MRS Corporate Partner Program supports the Materials Research Society Foundation.
Technique Well-defined control of the XY scanner in the Park NX10 AFM system and the Park SmartScan operation software allow the PinPoint Nanomechanical
Mode to provide high-speed F–d curves with accurate control of both contact force and time. The tip is lifted up before moving to the next pixel to prevent sample damage or tip wear due to the lateral force. Additionally, compared to the traditional AFM force-volume mode, which takes several hours to finish a 128 × 128 pixel image, PinPoint only takes several minutes to yield high-resolution topography images as well as maps of various mechanical properties such as stiffness, adhesion force, modulus, and deformation. The F–d curves collected at each pixel were fitted to the Hertz model, which due to the ease of use, has been extensively applied by the AFM
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Figure 1. PinPoint Nanomechanical images of collagen for (a) contrast enhanced height, (b) adhesion force, (c) modulus, and (d) stiffness images. (e) Module line profile averaged over the red rectangular area along the length of the collagen fibril in the image (c). Images: 256 × 256 pixel and scan size 10 μm × 10 μm.
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