A549 cell coating. (a) A549 cells cultured on the FNTD crystal surface starting to form a confluent monolayer. A typical island formation with branching cells is clearly visible. Scale bar, approximately 200 μ m (b) Magnified section of a confluent monolayer. The cells are tightly packed. It is difficult to contrast cells from the transparent crystal substrate with light microscopy. Scale bar, 10 μ m. (c) CM-DiI labeled and proliferating cells forming a confluent monolayer. Scale bar, approximately 200 μ m (d) Section of CM-DiI labeled monolayer reveals clear cytoplasmic coloring. Cytoplasmic granules (multilamellar bodies) exhibit a strong fluorescent signal. Scale bar, approximately 20 μ m. (e) Cell layer is labeled with Calcein AM to test cell viability. The outer red line indicates the cell membrane. The cell nucleus is defined by the inner red line. A strong perinuclear fluorescent signal with many bright spots (cytoplasmic organelles) and round nuclei indicate good cell viability. Scale bar, 20 μ m. (f) Immunofluorescent labeling of cell nuclei by HOECHST 33342 stain. A uniform monolayer of proliferating cells is visible. Scale bar, 10 μ m. Images (a), (c), and (d) were obtained by wide field microscopy whereas images (b, e, and f) were obtained in confocal fluorescent mode. Images (a)-(e) show live cell stainings. In (f) cells are fixed with 4% PFA.