Molecular recognition in a combined optical- AFM microscope for live cell studies

C. VON BILDERLING; M. CALDAROLA; M. E. MASIP; A. V. BRAGAS; L. I. PIETRASANTA

San Javier, Tucumán

Congreso; Reunión Anual de la Sociedad Argentina de Biofísica; 2012

Sociedad Argentina de Biofísica

Molecular recognition plays an essential role in the formation and function of biological systems. Several specific interactions can be observed including antigens and antibodies, enzymes and substrates, DNA promoters and transcription factors, ligands and receptors, which have high specificity and binding strength. These interactions are involved in many cellular functions and are of great interest for applications in molecular and cell biology, biophysics and nanotechnology. In recent years, optical microscopy and atomic force microscopy (AFM) techniques have both experienced significant progress. The motivation for combining fluorescence microscopy with AFM becomes visible from the need to exploit the complementary advantages of both techniques. Whereas fluorescence offers high temporal resolution and sensitivity to local physical chemistry, AFM provides a unique key to obtain topography images with nanoscale resolution, the possibility of mechanical manipulation and detection of single molecule interaction forces. In this work we present a combined optical-AFM microscope designed and assembled for the purpose of acquisition of topography/mechanics and fluorescence information on living cells. Contact mode, tapping mode imaging plus force spectroscopy are all available techniques in this microscope, which is suitable to work with samples in air and under liquid environments. The AFM head works on top of an inverted multipurpose optical microscope, which can operate as a wide field fluorescence microscope, a confocal fluorescence microscope or a multiphoton microscope. The combined microscope was tested and validated by successfully imaging of living cells. We also exploited the possibility of measuring interaction forces based on molecular recognition of the pair biotin-streptavidin.