Extension of spectral domain phase microscopy to three-dimensional nanoscale displacement mapping in cardiomyocytes

Abstract

Spectral domain phase microscopy (SDPM) is a functional extension of optical coherence tomography (OCT) whose common-path interferometric design enables phase-referenced imaging of dynamic samples. Like OCT, axial resolution in SDPM is determined by the source coherence length, while lateral resolution is limited by diffraction in the microscope optics. Nonetheless, the quantitative phase information SDPM generates is sensitive to sub-Angstrom displacements of scattering structures. Integrative quantitative phase imaging techniques, such as Fourier phase microscopy, Hilbert phase microscopy, and Digital holographic microscopy, have achieved sub-micron motion detection in live cells. In contrast with the techniques, SDPM can achieve full depth discrimination, allowing for resolution of the motion of independent, sub-cellular structures at various cross-sectional planes within the sample. The ability of SDPM to measure Doppler flow in single-celled organisms, time-resolved cellular motions, and rheological information of the cytoskeleton has been previously demonstrated. The objective of this study is to extend the use of SDPM to produce three-dimensional reconstructions of the internal and surface motions of beating cardiomyocytes. Phase information is used to the motion of quantify cellular structures in the axial dimension. Our gated acquisition process involves synchronization of the SDPM detection system with and applied electrical field used to stimulate beating in isolated cardiomyocytes. For a given pacing protocol, we obtain repeat motion measurements in two-dimensions during cellular contraction, building a volume image by repeating the process at multiple discrete slices through the cell. This experiment serves as a proof-of-principle for volumetric imaging of beating cardiomyocytes.