A key goal of this CRUK Accelerator is to study individual cell fate in 3D cell cultures, e.g., in response to chemotherapy, and to understand the heterogeneity in the response of cells to such interventions. To this end, it is necessary to resolve single cells and to track them over time. Whiles this can be undertaken using fluorescent labels of cellular structures, such labels can be toxic to the cells and the fluorescence process is itself phototoxic, which can limit the extent to which cell scan be imaged during time-lapse experiments. We are therefore exploring label-free approaches to image single cells with a view to track individual cell trajectories and to generate segmentation masks to be able to allocate detected fluorescence photons to specific cells.
As a first step, within the Photonics Group at Imperial, we have developed a novel single-shot, semi-quantitative phase imaging (QPI) method called polarisation-resolved differential phase contrast microscopy (pDPC) that utilises a novel polarisation-sensitive camera. pDPC can be implemented using low phototoxicity near infrared radiation and be readily integrated with fluorescence microscopes. For more information on pDPC, please click here. This method is currently implemented using transmitted light illumination and is most suitable for traditional 2D cell cultures. We are currently using this to explore the integration of QPI and FRET for long time-lapse single cell-resolved assays and are also developing a new QPI technique specifically for imaging 3D cancer models arrayed in multiwell plates.