Uncovering real-time interaction of polystyrene particles and cells from scales of Atlantic salmon by quantitative phase microscopy

The ubiquitous nature of microplastics in marine environments poses a significant threat to Atlantic salmon aquaculture, and fish in general. Mucosal surfaces are continuously exposed to microparticles – such as the skin epithelial layer with highly migrating keratocyte cells. This study applied the capabilities of Linnik-based Quantitative Phase Microscopy (QPM) equipped with a pseudo-thermal light source (PTLS) to examine the interactions between polystyrene microplastics (MPs) and Atlantic salmon keratocytes. The PTLS enables the QPM system to achieve high spatial phase sensitivity, allowing for the observation of precise morphological changes within the cell and migration in real time. Our study shows that cells that were exposed to polystyrene MPs exhibited dynamic fluctuations of the lamellipodia and provide evidence for early-stage phase membrane invaginations around the beads indicative of phagocytic activity. Implementation of QPM based on PTLS is a high-speed, non-invasive, label-free approach that provides vital insights into the morphological dynamics of MP exposure. This research not only contributes to the understanding of cellular morphological responses to microplastics in Atlantic salmon but also highlights the utility of advanced QPM imaging techniques from an environmental toxicology perspective.