Model s 2400

Representative samples (n=3) were primarily fixed in 2.5% glutaraldehyde (Sigma-Aldrich) for 2 h, followed by secondary fixation in 2% osmium tetroxide (Sigma-Aldrich) for another 2 h. The samples were then dehydrated in a gradient ethanol series, in hexamethyldisilazane (HMDS, Sigma-Aldrich) at a ratio of 1:1 with ethanol twice for 1 h each time, in HMDS at a ratio of 1:2 with ethanol overnight, and in HMDS three times for 4 h each time. The samples were air-dried for 24 h and gold sputter was added. The images were recorded by a scanning electron microscope (SEM) (Hitachi, Model S 2400).

Representative samples (n=2) were primarily fixed in 2.5% glutaraldehyde for 2 h followed by secondary fixation in 2% osmium tetroxide as described previously (Tan et al. 2010 (link)). The samples were then dehydrated consecutively in 25%, 50%, 75%, 95%, and 100% ethanol for 10 min each, in hexamethyldisilazane (HMDS) at a ratio of 1:1 with ethanol twice for 1 h each time, in HMDS at a ratio of 1:2 with ethanol overnight, and in HMDS three times for 4 h each time. The samples were air-dried for 24 h and gold sputter was added. The images were recorded by an SEM (Model S 2400; Hitachi, Brisbane, CA).

Representative samples (n=2) were first fixed in 2.5% glutaraldehyde (Sigma-Aldrich) for 2 h, followed by secondary fixation in 2% osmium tetroxide (Sigma-Aldrich) for another 2 h. After dehydration in a gradient ethanol series, the samples were treated by hexamethyldisilazane (HMDS, Sigma-Aldrich) at 1:1 with ethanol, 1:2 with ethanol, and HMDS alone, respectively, followed by air-drying for 24 h in a desiccator and addition of gold sputter. The images were taken using SEM (Hitachi, Model S 2400).