Abstract

The understanding of the interaction between biological specimen and new structured biomaterials is fundamental in the field of tissue engineering and tissue repair. The cross-talk interaction is induced by biological, topographic and mechanical cues and one of the challenge is the knowing of their infuelnce on cell fate. In biology and biomedical research fields one of the main topic is the understanding of morphology and mechanics of cells and microorganisms. Nowadays, one of the main tool is the study of the interaction with smart substrates. Biological samples present low amplitude contrast that limits the information that can be retrieved through optical bright-field microscope measurements. Optical transparency is overcame for fixed specimen by means of staining techniques but such well-established methods present the issue to be invasive and not applicable on live cells. Study of microorganism in their natural environment without perturbing their equilibrium is challenging in biology. When light passes thorough biological samples a little change in amplitude is due to their low absorption properties that is not sufficient to distinguish cellular and sub-cellular morphologies. The main effect on light propagating in such objects is in phase, indeed it is altered respect to the phase of the beam propagating in the surrounding medium. This is known as phase-retardation or phase-shift. Objects are visible by Phase Contrast Imaging (PCI) due to interferometric processes able to transform tiny phase variation in amplitude modulation so that any small differences in the beam optical path can be visualized. Common PCI methods are qualitative as they enhance the phase gradients but they cannot be connected to quantitative optical path variations. Digital Holography (DH) in microscopy present as a powerful tool to overcome all these issues. DH presents many advantages as high transversal and axial resolution and allows numerical aberration compensation and focus flexibility. The main characteristic is the possibility to discern between intensity and phase information performing quantitative mapping of the Optical Path Length (OPL). Up to now, DH has been considered as an innovative and alternative approach in microscopy and it’s a good candidate for complete specimen analysis in the framework of no invasive microscopy. In this paper, the flexibility of DH is employed to analyse in a completely and no-invasive way the cell mechanics of live and unstained cell subjected to appropriate stimuli. The potentialities of DH are employed to measure all the parameters useful to understand the deformations induced by external and controlled stress in living cells.

© 2013 IEEE