Digital Holographic Microscopy: A New Imaging Technique to Quantitatively Explore Cell Dynamics with Nanometer Sensitivity

In the first part of this chapter, we describe how the new concept of digital optics applied to the field of holographic microscopy has made it possible to quantitatively and accurately measure the phase retardation induced on the transmitted wavefront by the observed transparent specimen, allowing thus to develop a reliable and flexible digital holographic quantitative phase microscopy (DH-QPM). In the second part the most relevant DH-QPM applications in the field of cell biology are presented. Particularly, applications taking directly advantage of benefits provided by digital optics particularly off-line autofocusing and extended depth of focus, are outlined. Otherwise, special emphasis is placed on how important biophysical cell parameters including absolute cell volume, dry mass, protein content, transmembrane water movements, cell membrane fluctuations etc. can be derived from the quantitative phase signal (QPS) and used to characterize cell dynamics, analyze specific biological mechanisms and discriminate between physiological and pathophysiological states. In the last part, we present how transmembrane water movement measurements can be used to resolve neuronal network activity.