STUDYING THE SURFACE OF SOFT MATERIALS (LIVE CELLS) AT HIGH-RESOLUTION BY SCANNING PROBE MICROSCOPY - CHALLENGES FACED

The formation of transmembrane protein channels in the cells of multic ellular organisms is not well understood. These transmembrane channels play important roles in cell signal transduction and, in the case of gap junctions, (J.-P. Revel, J.H. Hoh, S.A. John, D.W. Laird, K.. Pura nam, S.B. Yancey, Cell Biol. 3 (1992) 21) intercellular communication. Obtaining high resolution images (less than 1 nm) of the surface of l iving cells (the plasma membrane) would contribute valuable informatio n towards understanding the formation of these channels. At present, a tomic or scanning force microscopy (AFM or SFM) shows the greatest pot ential for reaching this goal. AFM is able to obtain high resolution o n the surfaces of hard materials immersed in a solution. Thus, it is p ossible to image cells with AFM in an aqueous solution which mimics ph ysiological conditions, so they can remain alive. We have taken up thi s challenge and have found that interpreting data from imaging a cell surface at the nanoscale is difficult due to its soft material propert ies (when compared to the cantilever and probe materials). Therefore, a better understanding of the resolution achievable by AFM on sort mat erials is needed. The probe apex structure directly affects the resolu tion of AFM, so it is important to characterize it accurately (J.A. De Rose, J.-P. Revel, Microsc. Microanal. 3 (1997) 203). In addition, one needs to better understand the probe-sample interaction for AFM to im age highly deformable materials, such as cells, with reliable high res olution. We have studied AFM probe structure before and after use for imaging and the results have elucidated some information on the probe- sample interaction. (C) 1998 Elsevier Science S.A. All rights reserved .