Of silicon. Moreover, the 24 h culture time ensured a sufficient cell density with a few cells overlapping and without the need to replace the culture medium. To establish a more general finding relative to the capability of cells to actively colonize the deep gaps of silicon HAR PhCs, we investigated the behavior of eight cell lines with different morphology and adhesion properties. The MRC-5V1, CF and HT1080 lines are cells with a mesenchymal phenotype characterized by a spindle-shaped morphology with migratory protrusions and capability [34]. These cells are able to migrate as individual cells through the extracellular matrix to which they adhere, and rarely establish direct contact with neighboring cells. On the other hand, SW613-B3, HeLa, HCT116 and HT29 epithelial cells tend to form a sheet or Solvent Yellow 14 layers of cells that are tightly connected. Under normal conditions epithelial cells are unable to establish strong interactions with the underlying extracellular matrix. Finally, we exploited primary adenocarcinoma SW480 cells that, despite their epithelial origin, undergo the epithelial to mesenchymal transition (EMT) when grown at low density [35], and also in our experimental conditions they exhibited a mesenchymal behavior. As reported in Figure 2 for HT29 cell culture, as a representative example, the comparison among cells grown on flat silicon substrates (S), Figures 2c , or on conventional glass slides (glass), Figures 2a , showed no appreciable differences in cell density and/or morphology. These results are in agreement with the fact that the physico-chemical properties of a silicon surface are very similar to those of glass slides. Cells were cultured also on silicon dice incorporating the HAR PhC to investigate the effect of surface texture, as reported in Figures 2e for the same line. The image shows that the morphology of cells grown on deeply etched regions resembles the morphology exhibited by cells on flat silicon and glass slides. The use of dice that incorporate two different regions allows a direct comparison of the cell behavior on standardCell Culture on Silicon SamplesCell culture experiments were repeated several times, as previously described: the 24 h incubation of cells directly into the well ensured a sufficient cell density. Sterilized micromachined silicon devices fitting in 12-well plates were incubated as usual at 37uC in a humidified atmosphere containing 5 CO2 for 24 h, before fixing.Influence of “Cell Sedimentation”To evaluate the contribution of bare “cell sedimentation” on silicon device colonization, we performed the following tests: (a) a drop of cell suspension in isotonic medium (Phosphate Buffer Solution, PBS) without nutrients was placed on silicon, at the same cell concentration as previously described, and maintained at 37uC for 2 h; a drop of cell suspension was placed on silicon as in (a) but maintained at room temperature (at 20uC) for 2 h.(b)These experiments were designed to verify the eventual influence of spontaneous sedimentation, on cell penetration, inside the silicon grooves also as function of viscosity and/or temperature of the medium. Also these samples were, then, fixed and labelled as described in the next paragraph.Fluorescence Microscopy AnalysisAt the end of the incubation time, after the medium was removed, silicon dice were gently washed (twice) with PBS (0.1 M), finally replaced with cold (220uC) 70 ethanol (2 ml) for cell fixation. The silicon dice were Itacitinib chemical information stored after.Of silicon. Moreover, the 24 h culture time ensured a sufficient cell density with a few cells overlapping and without the need to replace the culture medium. To establish a more general finding relative to the capability of cells to actively colonize the deep gaps of silicon HAR PhCs, we investigated the behavior of eight cell lines with different morphology and adhesion properties. The MRC-5V1, CF and HT1080 lines are cells with a mesenchymal phenotype characterized by a spindle-shaped morphology with migratory protrusions and capability [34]. These cells are able to migrate as individual cells through the extracellular matrix to which they adhere, and rarely establish direct contact with neighboring cells. On the other hand, SW613-B3, HeLa, HCT116 and HT29 epithelial cells tend to form a sheet or layers of cells that are tightly connected. Under normal conditions epithelial cells are unable to establish strong interactions with the underlying extracellular matrix. Finally, we exploited primary adenocarcinoma SW480 cells that, despite their epithelial origin, undergo the epithelial to mesenchymal transition (EMT) when grown at low density [35], and also in our experimental conditions they exhibited a mesenchymal behavior. As reported in Figure 2 for HT29 cell culture, as a representative example, the comparison among cells grown on flat silicon substrates (S), Figures 2c , or on conventional glass slides (glass), Figures 2a , showed no appreciable differences in cell density and/or morphology. These results are in agreement with the fact that the physico-chemical properties of a silicon surface are very similar to those of glass slides. Cells were cultured also on silicon dice incorporating the HAR PhC to investigate the effect of surface texture, as reported in Figures 2e for the same line. The image shows that the morphology of cells grown on deeply etched regions resembles the morphology exhibited by cells on flat silicon and glass slides. The use of dice that incorporate two different regions allows a direct comparison of the cell behavior on standardCell Culture on Silicon SamplesCell culture experiments were repeated several times, as previously described: the 24 h incubation of cells directly into the well ensured a sufficient cell density. Sterilized micromachined silicon devices fitting in 12-well plates were incubated as usual at 37uC in a humidified atmosphere containing 5 CO2 for 24 h, before fixing.Influence of “Cell Sedimentation”To evaluate the contribution of bare “cell sedimentation” on silicon device colonization, we performed the following tests: (a) a drop of cell suspension in isotonic medium (Phosphate Buffer Solution, PBS) without nutrients was placed on silicon, at the same cell concentration as previously described, and maintained at 37uC for 2 h; a drop of cell suspension was placed on silicon as in (a) but maintained at room temperature (at 20uC) for 2 h.(b)These experiments were designed to verify the eventual influence of spontaneous sedimentation, on cell penetration, inside the silicon grooves also as function of viscosity and/or temperature of the medium. Also these samples were, then, fixed and labelled as described in the next paragraph.Fluorescence Microscopy AnalysisAt the end of the incubation time, after the medium was removed, silicon dice were gently washed (twice) with PBS (0.1 M), finally replaced with cold (220uC) 70 ethanol (2 ml) for cell fixation. The silicon dice were stored after.
