Effect of mechanical contact on the molecular recognition of biomolecules

Several developing technologies rely upon the activity of surface-bound biomolecules to control the functionality of an interface. The specificity of these biomolecules can be compromised by mechanical stresses present during their preparation or use. Moreover, many new biomechanical devices are also sensitive to mechanical stress. This paper is concerned with the direct assessment of the mechanical limits beyond which biomolecules are rendered inactive. These mechanical limits are evaluated by a combined approach involving an atomic force microscope (AFM), an optical microscope, and standard colorimetric techniques. The AFM is used to systematically stress micrometer-sized domains of biomolecule-laden surfaces; the results of which can be directly observed with an optical microscope following histochemical staining of the surface with biologically specific dyes. Using this method, we examined the limiting conditions of two benchmark systems, i.e., streptavidin and DNA. Because of the breadth of histochemical staining combined with the nature of the study, our approach is equally applicable to a wide range of biomolecular systems, perhaps even including the surfaces of living cells.