Mapping viscoelasticity, (specific) adhesion and near-field fluorescence of cellular structures with scanning probe microscopy

Abstract

One of the major features of scanning probe microscopy is the ability to produce high-resolution images in air and in liquid. This makes these microscopes potentially very useful for the study of biological materials. Indeed the number of reports that use these microscopes, especially the atomic force microscope (AFM), has increased exponentially in the past decade. However, in order to become a routine apparatus that is able to image live processes at a scale of a few nanometers, the instrumentation of the AFM has to be improved. First of all, under normal operation, the movement of the tip across the surface of fragile biological structures such as cell membranes, often results in movement or even destruction of the object. Secondly, the lack of specificity of the AFM makes it difficult to identify the observed structures. Other problems include the low imaging speed and problems associated with the tip-sample convolution. Here we will report on attempts to improve the first two points: sample destruction and specificity.It has become clear recently that for operation in air the so-called tapping mode AFM is much more gentle for the sample than the standard operation mode.