Lab-on-a-chip device for microfluidic trapping and TIRF imaging of single cells.

Total internal reflection fluorescence (TIRF) microscopy is a powerful imaging technique that visualizes the outer surface of specimens in close proximity to a substrate, yielding crucial insights in cell membrane compositions. TIRF plays a key role in single-cell studies but typically requires chemical fixation to ensure direct contact between the cell membrane and substrate, which can compromise cell viability and promote clustering. In this study, we present a microfluidic device with structures designed to trap single yeast cells and fix them in direct contact with the substrate surface to enable TIRF measurements on the cell membrane. The traps are fabricated using two-photon polymerization, allowing high-resolution printing of intricate structures that encapsulate cells in all three dimensions while maintaining exposure to the flow within the device. Our adaptable trap design allows us to reduce residual movement of trapped cells to a minimum while maintaining high trapping efficiencies. We identify the optimal structure configuration to trap single yeast cells and demonstrate that trapping efficiency can be tuned by modifying cell concentration and injection methods. Additionally, by replicating the cell trap design with soft hydrogel materials, we demonstrate the potential of our approach for further single-cell studies. The authors have no relevant financial or non-financial interests to disclose and no competing interests to declare.