Label-free full-field Doppler phase microscopy based on optical computation

The capability to image subtle mechanical motion at cellular and sub-cellular scales can be used to study how extracellular particles interact with cultured cells and, more generally, how cells interact with their environment. However, current technologies need to provide sufficient spatial resolution, temporal resolution, and motion sensitivity to image cellular and sub-cellular motion in the en face plane. To address this unmet need, we investigate a full-field Doppler phase microscopy (FF-DPM) technology based on an innovative optical computation strategy that enables depth-resolved imaging and phase quantification. In this study, we validated the motion tracking (displacements and velocities) capability of FF-DPM by imaging samples actuated by a piezo transducer (PZT). We demonstrated FF-DPM imaging of magnetic particles under different conditions with different motion characteristics. Our results show that free particles (suspended in a cell culture medium) had a significantly larger magnitude of motion than particles adhered to a cell. The key innovation of this study is the use of an optical computation strategy to perform depth-resolved phase quantification and Doppler measurement. The FF-DPM will have a significant impact, as it provides a unique capability to quantitatively measure subtle motion for models based on cultured cells.