Whole cell imaging based on wide-field interferometric phase microscopy and its application to cardiomyocytes

Whole cell imaging is a novel technique using which the time-dependent quantitative phase profiles of live unstained biological cells are analyzed numerically to learn on the cell functionally. Dynamic phase profiles of the sample are first acquired by wide-field digital interferometry (WFDI), a quantitative holographic approach, without the need for scanning or using exogenous contrast agents. The resulting phase profiles are proportional to the multiplication between the cell thickness profile and its integral refractive index profile. However, many morphological parameters, including cell volume and cell force distribution, are based on the cell thickness profile, rather than on its WFDI phase profile. For cells with heterogeneous refractive index structure, more than a single exposure is typically needed to decouple thickness from integral refractive index using the phase profile, with the risk of losing transient acquisition. The presented whole-cell-imaging approach show that the WFDI phase profiles are useful for numerically analyzing cells even in cases where decoupling of thickness and integral refractive index is not possible or desired. We thus define new numerical parameters that directly utilize the WFDI phase profile and demonstrate their usefulness for characterizing contracting cardiomyocytes, cells with complex and highly-dynamic refractive-index structure.