Real-time and non-invasive quantitative phase imaging of pancreatic ductal adenocarcinoma cell mechanical properties

Abstract

Cellular mechanical properties are known to influence both their cellular and subcellular functions. Whilst methods to assess cellular mechanics such as Atomic Force Microscopy (AFM) are already available, there is an emerging need to measure cellular mechanical properties in a label-free and contactless mode, to allow for long time monitoring of cell behaviour, and to enable measurements of cells embedded in extracellular matrix. In this study, we have employed Digital Holographic Microscopy (DHM) combined with the well-controlled application of hydrostatic pressure to study cellular mechanical properties in real-time and in a noncontact manner. Cyclic stress was applied non-destructively and non-invasively to pancreatic ductal adenocarcinoma Focal Adhesion Kinase (FAK) knockout cells (Panc47-1 -/-null) and their corresponding re-expressing clonal population (Panc47-1 +/+ wild type) within a 25cm2 culture flask by a microfluidic pump 24h after seeding. Cyclic stress was successfully applied directly to cells, and corresponding change in volume was recorded in real-time at the nanometre scale for cell, yielding the mechanical properties of the cells. Change in amplitude and/or frequency of the stimuli was translated to corresponding cell response. Differences were observed in relative strain rates between the cell lines under investigation. We have described a novel method to perform optical elastography on live cells at single cell resolution in realtime and non-destructively. This allows for long-term monitoring of mechanical properties during cell proliferation and differentiation, and disease progress. This can be directly related to the biomechanical properties of cells.