AFM on Biological Systems

Nanotechnology meets Life Sciences

With the ongoing progress in scanning probe techniques, nanometer- and even atomic-scale imaging became possible on a variety of different samples. On biological systems, however, the resolution is often limited by the intrinsic softness of the investigated materials. This drawback can be overcome by profiling samples with non-contact scanning force microscopy which have been immobilized using cryo-techniques. For this purpose, we developed an instrument specially suited for the investigation of soft biological matter at low temperatures.

Methods and Instrumentation

The microscope is mounted on a commercially available vibration isolation system and is integrated into an ultrahigh vacuum chamber. The vacuum system consists of a transfer chamber, a preparation chamber including a stage for in-situ freeze drying, freeze etching, or freeze fracturing, and the analysis chamber with the microscope. The transfer chamber allows besides its use as simple air lock also an exchange of the cold sample with cryo-electron microscopes. A flow cryostat cools the sample to the temperature of liquid nitrogen, while the tip is scanned. First test measurements on samples such as T4-bacteriophages (virus) are currently in progress.

Selected Publications

1. Pros and cons: cryo-electron microscopic evaluation of block faces versus cryo-sections from frozen-hydrated skin specimens prepared by different techniques
   T. Richter, S. S. Biel, M. Sattler, H. Wenck, K.-P. Wittern, R. Wiesendanger, and R. Wepf,
   J. Microsc. 225 (Pt 2), 201 (2007)
2. Dead but highly dynamic - the stratum corneum is divided into three hydration zones
   T. Richter, C. Peuckert, M. Sattler, K. König, I. Riemann, U. Hintze, K.-P. Wittern, R. Wiesendanger, and R. Wepf,
   Skin Pharmacology and Physiology 17, 246 (2004)
3. Frozen hydrated block face investigation of tissue for Cryo-SEM
   T. Richter, M. Sattler, R. Wiesendanger, K.-P. Wittern, and R. Wepf,
   Microscopy and Microanalysis 9 (Suppl. 2),p. 1546 (2003)
4. A cryogenic scanning force microscope for the characterization of frozen biological samples
   J.H. Müller, U.D. Schwarz, R. Wepf, and R. Wiesendanger,
   Appl. Phys. A 76, 893 (2003)
5. Investigation of the swelling of human skin cells in liquid media by tapping mode scanning force microscopy
   T. Richter, J. Müller, U.D. Schwarz, R. Wepf, and R. Wiesendanger, Appl. Phys. A 72 [Suppl.], 125 (2001)
6. Penetration pathways of fluorescent dyes in human hairfibres investigated by scanning near-field optical microscopy
   A. Kelch, S. Wessel, T. Will, U. Hintze, R. Wepf, and R. Wiesendanger,
   J. Microsc. 200, 179 (2000)



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