Comparison of polystyrene and hydrogel microcarriers for optical imaging of adherent cells
The ability to observe and monitor cell density and morphology has been imperative for assessing the health of a cell culture and for producing high quality, high yield cell cultures for decades. Microcarrier-based cultures, used for large-scale cellular expansion processes, are not compatible with traditional visualization-based methods such as widefield microscopy due to their thickness and material composition. Light-sheet tomography using label-free elastic scattering contrast from planar side illumination can achieve optical sectioning of thick samples, permitting non-invasive and non-destructive, in toto, three-dimensional, high-resolution visualization of cells cultured on microcarriers. Here, we assess the optical imaging capabilities of commercial polystyrene microcarriers versus custom-fabricated gelatin methacrylate (gelMA) microcarriers for non-destructive and non-invasive visualization of the entire microcarrier surface, direct cell enumeration, and sub-cellular visualization of mesenchymal stem/stromal cells (MSCs). The polystyrene microcarrier prevents visualization of cells on the distal half of the microcarrier using either fluorescence or elastic scattering contrast, whereas the gelMA microcarrier allows high fidelity visualization of cell morphology and quantification of cell density using light sheet fluorescence microscopy and tomography. The combination of optical-quality gelMA microcarriers and label-free light-sheet tomography will facilitate enhanced control of bioreactor-microcarrier cell culture processes.