Examining cardiomyocyte development with spectral domain phase microscopy

Phase-sensitive detection has long been recognized as a mechanism for increasing imaging contrast. The proliferation of quantitative phase contrast techniques and the breadth of emerging applications reflects the potential for achieving subdiffraction-limited resolution of cellular structure and dynamic phenomena with phase. Our laboratory developed spectral domain phase microscopy (SDPM) as a simple, phase-stable tool for studying cell dynamics and structure. As a functional extension of optical coherence tomography (OCT), SDPM inherited the high-resolution depth-sectioning capabilities for which OCT is well known, but adds to this an ability to discriminate sub-coherence length changes in optical pathlength within target samples at discrete axial positions. Early demonstrations of SDPM showed it to be extremely sensitive to thickness changes in biological and non-biological samples; the results of our previous studies investigating cell surface motion in cardiomyocyte contractility, cytoplasmic streaming rates in single-celled organisms, and rheological properties of the cytoskeleton suggest that SDPM can contribute insights of biological relevance. The principal aim of this work is to refine SDPM to enable imaging, interrogation, and quantification of parameters of interest in developing cardiomyocytes. In this manuscript, we report on the technology advances that enable multidimensional SDPM, and the results of new inotropic imaging studies of chick embryo cardiomyocytes.