High-speed atomic force microscopy for nano-visualization of dynamic biomolecular processes

The atomic force microscope (AFM) has a unique capability of allowing the high-resolution imaging of biological samples on substratum surfaces in physiological solutions. Recent technological progress of AFM in biological research has resulted in remarkable improvements in both the imaging rate and the tip force acting on the sample. These improvements have enabled the direct visualization of dynamic structural changes and dynamic interactions occurring in individual biological macromolecules, which is currently not possible with other techniques. Therefore, high-speed AFM is expected to have a revolutionary impact on biological sciences. In addition, the recently achieved atomic-resolution in liquids will further expand the usefulness of AFM in biological research. In this article, we first describe the various capabilities required of AFM in biological sciences, which is followed by a detailed description of various devices and techniques developed for high-speed AFM and atomic-resolution in-liquid AFM. We then describe various imaging studies performed using our cutting-edge microscopes and their current capabilities as well as their limitations, and conclude by discussing the future prospects of AFM as an imaging tool in biological research. 2008 Elsevier Ltd. All rights reserved. 0079-6816/$ see front matter 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.progsurf.2008.09.001 * Corresponding author. Address: Department of Physics, Kanazawa University, Kakuma-machi, Kanazawa 920-1192, Japan. Tel.: +81 76 264 5663; fax: +81 76 264 5739. E-mail address: [email protected] (T. Ando). 338 T. Ando et al. / Progress in Surface Science 83 (2008) 337–437